tag:blogger.com,1999:blog-9428327085934106582024-03-12T11:13:56.227+00:00False ElectronicsOccasional repairs, builds, teardowns. At War With False Electronics.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.comBlogger54125tag:blogger.com,1999:blog-942832708593410658.post-26778146907335392332020-07-14T15:08:00.001+01:002020-07-14T15:09:16.619+01:00DOD American Metal<div>Another quick one. This American Metal would power up, pass a clean signal but wouldn't pass an effected signal.<br /></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguEwn-4t5iacz_HQqHGJbyV84M4K6ZYJJxnSUEuRBCy0WtjwnH6fJxyBysWRmC6dYW8X0h2l2yDxBlmFjFWPbn2YEp_KnoPh1BpOmT_gpF9aJU4QPYAop0Qf4W85dU0pU55-Q5YvIIinkC/s2048/IMG_20200524_171728075.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguEwn-4t5iacz_HQqHGJbyV84M4K6ZYJJxnSUEuRBCy0WtjwnH6fJxyBysWRmC6dYW8X0h2l2yDxBlmFjFWPbn2YEp_KnoPh1BpOmT_gpF9aJU4QPYAop0Qf4W85dU0pU55-Q5YvIIinkC/w300-h400/IMG_20200524_171728075.jpg" width="300" /></a></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Schematics are older DOD pedals aren't too hard to come by (I believe some of them were supplied in the original boxes). I suspected a bad switching JFET was blocking signal, but they all measured fine on the oscilloscope.<br /></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfAgLDGDyWYeAxb-KH661ieaJiXuHGYeBiYcRbUJ6zLnfUrc_uRpbcugk240YUtXh6c8fcQh4It6ZhPe_WCbCkYX_ObztwlIZLI5nyR16cIqeIIS9U0TWW5sTtfhME_JU9Dnzf0z0z-vDA/s1588/fx56.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1137" data-original-width="1588" height="286" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfAgLDGDyWYeAxb-KH661ieaJiXuHGYeBiYcRbUJ6zLnfUrc_uRpbcugk240YUtXh6c8fcQh4It6ZhPe_WCbCkYX_ObztwlIZLI5nyR16cIqeIIS9U0TWW5sTtfhME_JU9Dnzf0z0z-vDA/w400-h286/fx56.jpg" width="400" /></a></div><div><br /></div><div>I found that two of the transistors near the distortion control had very little voltage on the collectors. The schematic shows a series 1k resistor and a 47uF capacitor from the 9V supply, so there's a good chance that capacitor is shorted.<br /></div><div><br /></div><br /><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-hzZTb4meWLt3fvV1uCIgsRnZBPbe2Edfv5RKexylrMDVexgEXmX7mswfHgsbULqo7BqARYNSv1dsgVvBUKCCRLbBjRhgqd_b2Oyn644wtGktYfW2CtJekJJ9G_gqYUpJDo09Jl-o6X5g/s556/schem-crop.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="474" data-original-width="556" height="341" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-hzZTb4meWLt3fvV1uCIgsRnZBPbe2Edfv5RKexylrMDVexgEXmX7mswfHgsbULqo7BqARYNSv1dsgVvBUKCCRLbBjRhgqd_b2Oyn644wtGktYfW2CtJekJJ9G_gqYUpJDo09Jl-o6X5g/w400-h341/schem-crop.jpg" width="400" /><br /></a></div><div><br /></div><div>The 47uF is right in the middle of the PCB. Pulling out brought back the effected signal, so I replaced it and put things back together.<br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-hzZTb4meWLt3fvV1uCIgsRnZBPbe2Edfv5RKexylrMDVexgEXmX7mswfHgsbULqo7BqARYNSv1dsgVvBUKCCRLbBjRhgqd_b2Oyn644wtGktYfW2CtJekJJ9G_gqYUpJDo09Jl-o6X5g/s556/schem-crop.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZgUPz0JXcmIkD6-Xu4ymvWWUm815UGixufPj4COTEyZfUMJo74LlTgSCJz7BGErmM0LHBCidNmX8ghuwQJSb11fOLfFXJ9kTQSqBb__ugOf652-Hpj6mMwOOfgRyFeRy9YzSuULdo3VBW/s2048/IMG_20200524_142559218.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2048" data-original-width="1536" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZgUPz0JXcmIkD6-Xu4ymvWWUm815UGixufPj4COTEyZfUMJo74LlTgSCJz7BGErmM0LHBCidNmX8ghuwQJSb11fOLfFXJ9kTQSqBb__ugOf652-Hpj6mMwOOfgRyFeRy9YzSuULdo3VBW/w300-h400/IMG_20200524_142559218.jpg" width="300" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">This is a very cool pedal, definitely in the HM-2 family. Maybe not as much gain and not as much EQ control, but it certainly does the buzzsaw sound when turned up.<br /></div>krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com13tag:blogger.com,1999:blog-942832708593410658.post-15030095161652763352020-07-13T21:09:00.001+01:002020-07-13T21:10:48.751+01:00Digitech PDS 8000<div class="separator">I got this one for completeness sake after looking at the other PDS series.<br /></div><div class="separator"><br /></div><br /><div style="text-align: center;"></div><div class="separator" style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0MieJWwvUJ0bdyxwGqxxlhASzTfwDU0SOsxtVukxyIhJbcWGjcNoQEoM0sOxetcwLdwtPZFJspWbb2nJyGw4dzqF8P4Hc7BERRgoBAGKJjgbJsM9eIxPVUKB4-VP195aST1tnFQ6NO_f_/s2048/IMG_20200620_132159505.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0MieJWwvUJ0bdyxwGqxxlhASzTfwDU0SOsxtVukxyIhJbcWGjcNoQEoM0sOxetcwLdwtPZFJspWbb2nJyGw4dzqF8P4Hc7BERRgoBAGKJjgbJsM9eIxPVUKB4-VP195aST1tnFQ6NO_f_/w400-h300/IMG_20200620_132159505.jpg" width="400" /><br /></a></div><div class="separator"><br /></div><div class="separator">The insides are very similar to the PDS 2000, with 4 times the memory. The <a href="https://drive.google.com/file/d/1tRAnF3jEh3PUPlnmjdFkNmH94DAiXzx-/view?usp=sharing">PDS 8000 schematic is online</a>, but the quality of the scan is so poor that the 2000 schematic is probably more useful.<br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqy_QCnIMOBduk9kFC2o5aO0Rw3F8DX1LNVUQXflVzEpyb5PP1KMTEVsGRUpJhoogHGzwAbOTCXkdlTUF1SLdX1mTYeMqILJ-qJpP_SHKK5zaQ8F_vcDsanpgP-qQAjsJ2JBxoIPFRiKnQ/s2048/IMG_20200620_132159505.jpg" style="margin-left: 1em; margin-right: 1em;"></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9DUyFE2Ezo0uLICjlUNWlZu13DzmeONgtHIYwGkKFRRb_nL3A0U_iZ3CLgYm_RsCT1beW3jFi-u62Ahl7qHVneHOxKBaG2ggNO2jH6AYV9ZN-IvAsG3RQM-PD_z40-S1QD_c9N3ZbkYEU/s2048/IMG_20200620_132142483.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9DUyFE2Ezo0uLICjlUNWlZu13DzmeONgtHIYwGkKFRRb_nL3A0U_iZ3CLgYm_RsCT1beW3jFi-u62Ahl7qHVneHOxKBaG2ggNO2jH6AYV9ZN-IvAsG3RQM-PD_z40-S1QD_c9N3ZbkYEU/w400-h300/IMG_20200620_132142483.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">As arrived, no activity. The reverse polarity diode was shorted, after clipping it out I had 5V at the digital chips but no 9V at any of the analog stuff.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">I knew that the 9V supply has a soft-start circuit (as in the 2000) - the JFET was also dead. With a repaired soft-start, the 9V rail was shorted to ground. There is only one 470 uF electrolytic capacitor from 9V to ground, replacing this fixed the pedal. It also got new footswitches as the old ones were prettyy unreliable.<br /></div>krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com11tag:blogger.com,1999:blog-942832708593410658.post-65045223137655888172019-03-28T18:41:00.001+00:002019-03-28T18:41:43.044+00:00Electro-Harmonix Micro PogI think this is the last entry in the EHX POG series that I haven't
repaired. As usual, this came from eBay and doesn't work. No signs of
life.<br /><br />
<div style="text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcVvVhL1vrh-Pw8QAt5Mn0nM9ebyONesYWURvIcETtVB8FtEJ8w9Ogwa0lL7ZeaNz5Zw7c1OgM6KB58LWgvSi8IknhsrAgeB2u8gsvt44I1vw-JnbUP1u9XuL9HXFx3wcOo6R7UzvR3P7g/s1600/micro_pog.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1355" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcVvVhL1vrh-Pw8QAt5Mn0nM9ebyONesYWURvIcETtVB8FtEJ8w9Ogwa0lL7ZeaNz5Zw7c1OgM6KB58LWgvSi8IknhsrAgeB2u8gsvt44I1vw-JnbUP1u9XuL9HXFx3wcOo6R7UzvR3P7g/s400/micro_pog.jpeg" width="338" /></a> </div>
<br />
On
first inspection, it looks like the diode in the switching power supply
is trying to escape the PCB. I don't think that overheating could cause
this without scorching the board, someone probably attempted to
desolder this. My multimeter confirmed that this diode was a short
circuit, so that's probably the fault. The diode is an <a href="https://uk.farnell.com/on-semiconductor/ss14/diode-schottky-1a-40v-smd/dp/1467537">SS14</a>, which is also the same part used for input polarity protection. The switching IC is a <a href="https://www.onsemi.com/PowerSolutions/product.do?id=CS51413">CS51413</a> buck regulator.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4hdMkeJ3rfWRJUlq4S9qL1FvluZPfLZq8Yb81cwSSWi9QXHuN61odztqCcAEoaOONF1Nn9t1nbDWDH0s67S-hNaztxlkw0kbxhhyphenhyphenV_zDAD8OLugG07hLeHZnICr-R6PmuYJlgk3ZbJATp/s1600/bad_diode.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1322" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4hdMkeJ3rfWRJUlq4S9qL1FvluZPfLZq8Yb81cwSSWi9QXHuN61odztqCcAEoaOONF1Nn9t1nbDWDH0s67S-hNaztxlkw0kbxhhyphenhyphenV_zDAD8OLugG07hLeHZnICr-R6PmuYJlgk3ZbJATp/s400/bad_diode.jpeg" width="330" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
I removed the diode and still measured a short across it's pads, so the switching chip is probably bad. That came off as well.</div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div style="text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRD93VycdwL8RnKIWdksZgecmuV6bT_6YmnzX4-Ckc3iC89LSDFf0-WCOIG0lbIeE-Ro6hsoBsN4voveWvt6_VUO-StI6APVjLQe3CnwCKHFaon11Xz3d6bJHOwvZEAjecnnqyVfNsstgP/s1600/pulled_parts.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1403" data-original-width="1600" height="350" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRD93VycdwL8RnKIWdksZgecmuV6bT_6YmnzX4-Ckc3iC89LSDFf0-WCOIG0lbIeE-Ro6hsoBsN4voveWvt6_VUO-StI6APVjLQe3CnwCKHFaon11Xz3d6bJHOwvZEAjecnnqyVfNsstgP/s400/pulled_parts.jpeg" width="400" /></a><br />
<br />
<div style="text-align: left;">
I
ordered a replacement CS51413 but actually received a CS51414, which
was annoying. However, the CS51313 and CS51414 are very similar, the
'313 has an external sync pin where the '514 has an external bias pin.
The Micro POG doesn't actually route pins 4 & 5 anywhere, so either
chip can be used. I suspect that both are the actually the same die,
with different pads broken out to external pins.</div>
<div style="text-align: left;">
<br /></div>
<div style="text-align: left;">
After
replacing the controller IC and the switching diode, I still had a
short from output voltage to ground. The output capacitor (C3) is also
connected across these nodes, so I removed it and then the pedal worked.
C3 is filtering the output of the 3.3V switching supply and doesn't
seem to be always necessary. I don't know the value of C3, but the
datasheet recommends 100uF. A 100uF ceramic capacitor in this package is
actually quite expensive, so I used a 47uF.</div>
<div style="text-align: left;">
<br /></div>
</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7PzkHJ8IzWqWej5bpzHm3QDxU_K6-EFLiklw8omayU5XaSn0_3a-yx9x-UeWaobjNo_K_KADbPLv2z_cSCD7zINCWBop1Nj_DvHZKSDnBAXY2pR2rx9qE8pZEOlCf-jyXctsSHKzVRuRQ/s1600/pcb_componentside.JPeG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1461" data-original-width="1600" height="365" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7PzkHJ8IzWqWej5bpzHm3QDxU_K6-EFLiklw8omayU5XaSn0_3a-yx9x-UeWaobjNo_K_KADbPLv2z_cSCD7zINCWBop1Nj_DvHZKSDnBAXY2pR2rx9qE8pZEOlCf-jyXctsSHKzVRuRQ/s400/pcb_componentside.JPeG" width="400" /></a></div>
<br />
The
rest of the pedal is very similar to other Electro-Harmonix XO series
units. There's a PIC18F2431 microcontroller, a DSP56364AF100 DSP and a
PCM3052A audio codec.<br />
<br />
<div style="text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRzBLbwZRIl1jrDXmPQvLQKTgvUGqjHBYZDypnHxc-4TZcGtXgdACceVzqGhaNiebjZcz0IQq4DiTTB0mkEXZNWCid_vUvgSMD8kNarOb7gbFy760QpgKLhqfOem5nmqgTqZ2SlWaOSMlL/s1600/backside_pcb.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1597" data-original-width="1600" height="398" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRzBLbwZRIl1jrDXmPQvLQKTgvUGqjHBYZDypnHxc-4TZcGtXgdACceVzqGhaNiebjZcz0IQq4DiTTB0mkEXZNWCid_vUvgSMD8kNarOb7gbFy760QpgKLhqfOem5nmqgTqZ2SlWaOSMlL/s400/backside_pcb.jpeg" width="400" /></a> </div>
<br />
When
I had this working the "Octave Up" pot felt a bit weird. The shaft had
actually broken away form the pot and had been re-inserted. I replaced
it with a new 5Kohm part from Smallbear which is an almost perfect
match.<br />
<br />
<div style="text-align: center;">
<img border="0" data-original-height="1325" data-original-width="1600" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-cXH-JqkYCdqVxETuo3INBsoHPTm16hHr2wDK37owVLxasRxvxe8N0fC9elnvtrJvY_AhvVMynEPy8sz3AOuSotodKLQCEPZqerNUES2ipxHqJ_JXSvMyMek3V4Don9sK3fJHqT49D8RM/s400/after.jpeg" width="400" /></div>
<div style="text-align: left;">
</div>
<div style="text-align: left;">
That's it. Maybe someday I'll look at the HOG series as well. </div>
krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com20tag:blogger.com,1999:blog-942832708593410658.post-72499675968250325722019-03-15T13:32:00.001+00:002019-03-15T13:32:32.940+00:00Yamaha QY20After fixing the MS-20 I was having a lot of fun with it, but really wanted some kind of sequencer. I would have preferred not to have to rely on a laptop and was looking for something small and cheap.<br />
<br />
I found this Yamaha QY20 on sale from a Japanese eBay seller, listing as non-functional. It was a portable sequencing device from the early 90s, with some workstation-style sounds and MIDI I/O. The service manual was available online, it was very cheap and it looked like a decent form-factor so I took a chance.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEge32LDO2Hq5dT7U1oQ5gsY_7Kf7qTtxfoalMRejWGFKfOTIKjbwxlTqCWRPd6H1V4mZBW6FhyphenhyphenG5UkX6a15f5xKfA6T2KjGkH3D9d5Aa7jbBNpnzfAdd5ZNGRVVKoDTSVO83njaLWnuJZlw/s1600/qy20.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1055" data-original-width="1600" height="263" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEge32LDO2Hq5dT7U1oQ5gsY_7Kf7qTtxfoalMRejWGFKfOTIKjbwxlTqCWRPd6H1V4mZBW6FhyphenhyphenG5UkX6a15f5xKfA6T2KjGkH3D9d5Aa7jbBNpnzfAdd5ZNGRVVKoDTSVO83njaLWnuJZlw/s400/qy20.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Yamaha QY20, with carry case</td></tr>
</tbody></table>
<br />
I applied 12V from a bench power supply to the DC jack - it pulled around 135 mA but didn't show any sign of life. However, when I connected the headphone jack to a speaker and pushed some keys I could hear a piano. I could also connect up the MS-20 by MIDI and trigger notes using the QY20 keys. It looked like the there was just an issue with the display.<br />
<br />
Usually LCD displays have a bias voltage supply that is much more positive or negative than the supply for the logic chips. I expected a bad switching power supply. The <a href="https://elektrotanya.com/yamaha_qy-20_sm.pdf/download.html">service manual</a> is very comprehensive and has a complete schematic, it shows a MAX680 inverting charge pump generating a negative supply of -9.3 to -9.6V from the 5V rail. Either the charge pump has failed, or the contrast pot has gone open circuit.<br />
<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyX2U2zcOVewefscutQMg79sce7Ot-flJUTId3bV6Mr37xrKesEBSpSfJ-1Jo9btRqNgdpEfuhAKKoI-T1N0HMqskwzOG0_UhBAUOzoI5r96xkpaQqajhfFbXFbEdtm5qoNixNp6puE4tY/s1600/vee_schematic.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="467" data-original-width="821" height="227" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyX2U2zcOVewefscutQMg79sce7Ot-flJUTId3bV6Mr37xrKesEBSpSfJ-1Jo9btRqNgdpEfuhAKKoI-T1N0HMqskwzOG0_UhBAUOzoI5r96xkpaQqajhfFbXFbEdtm5qoNixNp6puE4tY/s400/vee_schematic.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">LCD bias supply schematic, from service manual.</td></tr>
</tbody></table>
<br />
It's fairly easy to take apart the QY20, but there is a copper sheet for shielding that needs to be desoldered.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4VtlCXBsvRvJUErVMykdyhetRnTXLP7LazXH6IdDLWJyqDseSzj4purajg8eFOwCh5agofpbqw7-vxDNKlChyphenhyphenXzJCDfjGWFbXpXG32_vskJDPg-qGwWYj1LSBU8GVA0RXNWV6fpnScram/s1600/IMG_20190312_175930442.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4VtlCXBsvRvJUErVMykdyhetRnTXLP7LazXH6IdDLWJyqDseSzj4purajg8eFOwCh5agofpbqw7-vxDNKlChyphenhyphenXzJCDfjGWFbXpXG32_vskJDPg-qGwWYj1LSBU8GVA0RXNWV6fpnScram/s320/IMG_20190312_175930442.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shielding has to be desoldered at the MIDI and line output connectors.<br />
</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwYrtg3pvID_d-1KSE96pMKlBDChGnia5eRrtzO7UfwAYlNv4tw4RK16GexhgD47LX1v0ZD5P4H4jge_WowQJYB315I6IhXmtbY1KELqrShPbJISzHHUN1rTVu4yrki0OHWmlEmjUAmSmT/s1600/pcb.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="697" data-original-width="1600" height="173" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwYrtg3pvID_d-1KSE96pMKlBDChGnia5eRrtzO7UfwAYlNv4tw4RK16GexhgD47LX1v0ZD5P4H4jge_WowQJYB315I6IhXmtbY1KELqrShPbJISzHHUN1rTVu4yrki0OHWmlEmjUAmSmT/s400/pcb.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Digital and audio PCB</td></tr>
</tbody></table>
The insides are fairly typical surface mount construction for early 90s, particularly for a portable unit.<br /><br />Funnily enough, the microcontroler is a H8/520, the same family used in the MS-20 20+ years later. The main soundchip is a YMW-258-F "AWM & FM Tone Generator", which is likely to be some variant on the chips Yamaha were doing for synths and video games at the time.<br />
<br />
I measured the Vee bias voltage for the LCD at only -5 V. It should be closer to -10V, as the MAX680 charge pump is an inverting and voltage doubling converter. I would guess that one switching stage inside the MAX680 is bad and it is only inverting.<br />
<br />
I removed the MAX680 (looks like I forgot to take a picture of this, it's a SOIC 8 chip on the backside of the board) and the 4 22 uF switching capacitors (C26,C27,C28,C29).<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVR_au_Wz7rOKC8sot8m27E_vHCXaOiT1DWG2ssm7GbpbqBYNGcBXju4pFUSaVrXrsORcAOuY76RUdtfd43gsuBsvOIBsBE3n2tTgnHOzeB_sNaDTypdW-NX2dheRVnhru6m0U0vv7YUlO/s1600/IMG_1637.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVR_au_Wz7rOKC8sot8m27E_vHCXaOiT1DWG2ssm7GbpbqBYNGcBXju4pFUSaVrXrsORcAOuY76RUdtfd43gsuBsvOIBsBE3n2tTgnHOzeB_sNaDTypdW-NX2dheRVnhru6m0U0vv7YUlO/s400/IMG_1637.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">C26-C29 removed</td></tr>
</tbody></table>
After installing new parts, Vee was now -9.2V - a little bit low, but certainly a change. When I re-attached the LCD board, the display worked again.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEEq3J5r1pLh7_6ByNQajledE5eMYt0TZ9Uts9WQtnVNxy6j5oScl1xX_N1I8OKfqwwnM4vgmrOluOmavBYnlgtOcPRBDJ_BvBy5n0zrXB7E0vWD_rZ22iVWKLDkIr4od1MIC9mC2CGDSM/s1600/IMG_1640.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEEq3J5r1pLh7_6ByNQajledE5eMYt0TZ9Uts9WQtnVNxy6j5oScl1xX_N1I8OKfqwwnM4vgmrOluOmavBYnlgtOcPRBDJ_BvBy5n0zrXB7E0vWD_rZ22iVWKLDkIr4od1MIC9mC2CGDSM/s320/IMG_1640.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Reflective LCDs are surprisingly difficult to photograph,</td></tr>
</tbody></table>
I can change the cheesy electric piano to 100+ other throwback workstation sounds! Time to learn how to use this as a MIDI sequencer.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com15tag:blogger.com,1999:blog-942832708593410658.post-47681355091493331352019-03-12T21:57:00.001+00:002019-03-12T21:57:12.781+00:00Korg MS20 Mini<h2>
Korg MS-20 Mini Repair:</h2>
<br />
I have wanted one of these since they were first released, but ended up waiting until a broken one came along. I probably overpaid a little for this, but the fixes weren't too bad.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhONtUmJhXFLeo_4x02LHRewqACcaGb8u9J3D0k7Fgb8uB-3UcKNn1th9N4eQCVrGWUG3342E1S1Ctc2lBWO1LFxBClEk5Qa_JpkSpKXA07qVrjVCNaXkoWdluYLu6vYmLo1T7JZRWFSw1u/s1600/ms20.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="709" data-original-width="1600" height="176" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhONtUmJhXFLeo_4x02LHRewqACcaGb8u9J3D0k7Fgb8uB-3UcKNn1th9N4eQCVrGWUG3342E1S1Ctc2lBWO1LFxBClEk5Qa_JpkSpKXA07qVrjVCNaXkoWdluYLu6vYmLo1T7JZRWFSw1u/s400/ms20.jpeg" width="400" /></a></div>
<br />This came from eBay, the seller had bought it as faulty with a non-functioning headphone output. When they received it they found it wouldn't power up, so they sold it on again. I am expecting some kind of power fault and something else wrong with the headphone output.<br />
<br />
Despite the popularity of this synth and the number of mods documented online, there isn't a lot of information on some of the parts used, so hopefully this will be useful to others.<br />
<br />
There are 3 main PCBs, all mounted to the sheet metal case and connected together with cables.<br />
<ol>
<li>Digital board - power entry and power supplies, the microcontroller, MIDI and USB ports.</li>
<li>Analog board - all synthesizer circuits, knobs, switches and jacks.</li>
<li>Keyboard PCB - breaks out the keys to a connector. I didn't look at this. </li>
</ol>
<h2>
Digital Board (KLM-3163C):</h2>
<br />
The digital board is the largest difference between the Mini and the original MS-20, and unfortunately there is no available manual or schematic.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhN5C6tp6cHoyq7i3KpIZPDRtDzbYJMbQYUhV4zTBXmvp5S-JV42YY6LSqW6pz9IS49fR8LwCuDZ_C3aZvT34Mey5Wk8EiWG400GbnARE1g1VZuIXME0n-zvdlxSGcI1S90vkuPPyRjY8uD/s1600/digital_board.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="611" data-original-width="1600" height="152" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhN5C6tp6cHoyq7i3KpIZPDRtDzbYJMbQYUhV4zTBXmvp5S-JV42YY6LSqW6pz9IS49fR8LwCuDZ_C3aZvT34Mey5Wk8EiWG400GbnARE1g1VZuIXME0n-zvdlxSGcI1S90vkuPPyRjY8uD/s400/digital_board.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">KLM-3163C</td></tr>
</tbody></table>
<br />
There is a switching power supply on the left hand side of the image, the large transformer/dual inductor is a give-away. The microcontroller (IC3) is right next to the keyboard connector and all the pins are routed right to it, so it is doing keyboard-scanning as well as USB and MIDI.<br />
<br />
I applied power and found that there was no voltage at the switch mode power supply inputs, and therefore nothing powering the analog board.<br />
<br />
There is a component marked "F2" that is connected to both the SMPS input and the incoming 9V. Despite the silkscreen, I was pretty sure this was a P-channel FET and not a fuse. IC50 is a CD4011 Quad NAND which is powered by 9V - I am fairly certain this uses some surrounding resistors, capacitors and transistors as a timing circuit to turn on the P-FET gate a short amount of time after power is applied. This works as a "soft-start" and limits the inrush current.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitb-5Dt22sdAWxGn8qjrznT72upG2dKwpdqtMsGmWoByFyuQzS0Bfy_E7XfuizMx5CnVBH7KgchmICHEuNWrfn8vXyoYhLhyR60fV3TMVivCDjF-q6CeL23LLsUlpsIS0UWBpW3Dgx3Ecd/s1600/IMG_1598.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitb-5Dt22sdAWxGn8qjrznT72upG2dKwpdqtMsGmWoByFyuQzS0Bfy_E7XfuizMx5CnVBH7KgchmICHEuNWrfn8vXyoYhLhyR60fV3TMVivCDjF-q6CeL23LLsUlpsIS0UWBpW3Dgx3Ecd/s320/IMG_1598.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Temporary fix to get things working</td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
<br />
To test this, I just shorted across the FET and connected power to the
switching power supply chip. This worked, I now had +14.5V and -14.5V
rails, and when I connected everything back together the synth worked
when using the main output jack, but not the headphone jack.<br />
<br />
I later confirmed the part number of F2 and replaced it.<br />
<br />
Here are part numbers for all the ICs and transistors, from my notes:<br />
<br />
F2 (?) - RRL025P03 - Pch -30V -2.5A Power MOSFET - used for power supply polarity protection. Amusing numerated "F2".<br />
<a href="http://www.farnell.com/datasheets/2706699.pdf">http://www.farnell.com/datasheets/2706699.pdf</a><br />
<br />
IC1 - R1154H036B - 3.6V voltage regulator. MCU (IC3) runs at 3.6V.<br />
<a href="https://www.mouser.com/datasheet/2/792/r1154-ea-923729.pdf">https://www.mouser.com/datasheet/2/792/r1154-ea-923729.pdf</a><br />
<br />
DT1 - DT4 - 2DTC114 digital transistors, marked "24" - used in other Korgs.<br />
<a href="https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e">https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e</a><br />
<a href="http://pdf1.alldatasheet.com/datasheet-pdf/view/201787/RICOH/R1154H036B.html">http://pdf1.alldatasheet.com/datasheet-pdf/view/201787/RICOH/R1154H036B.html</a><br />
<br />
IC2
- BU4227 - marked YU, used in other Korgs. This is an under-voltage
detector, it resets the MCU if the supply voltage drops below 2.7V. <br />
<a href="https://www.rohm.com.tw/datasheet/BU4325G/bu42xxg-e">https://www.rohm.com.tw/datasheet/BU4325G/bu42xxg-e</a><br />
<a href="http://rohmfs.rohm.com/en/products/databook/datasheet/ic/power/voltage_detector/bu42xxg-e.pdf">http://rohmfs.rohm.com/en/products/databook/datasheet/ic/power/voltage_detector/bu42xxg-e.pdf </a><br />
<br />
IC3 - H8S/2210C - main microcontroller, covers keyboard scanning, USB & MIDI.<br />
<a href="http://pdf.datasheetz.com/data/Integrated%20Circuits%20(ICs)/Microcontrollers/HD6473042F16-datasheetz.pdf">http://pdf.datasheetz.com/data/Integrated%20Circuits%20(ICs)/Microcontrollers/HD6473042F16-datasheetz.pdf</a><br />
<br />
IC9 - JRC 4558 - opamp, not sure what this is doing.<br />
<br />
IC44 - 74LVC1G126DCKRG4 - Single Bus Buffer Gate, marked CN5, also used in Kronos.<br />
<a href="http://www.ti.com/lit/ds/symlink/sn74lvc1g126.pdf">http://www.ti.com/lit/ds/symlink/sn74lvc1g126.pdf</a><br />
<br />IC47 - TPS54240 3.5-V to 42-V Step-Down DC - DC Converter With Eco-Mode™ - uses an onboard transformer to generator the analog voltage rails, which are regulated down further by IC49 and IC53, probably to clean up the switching noise.<br />
<a href="http://www.ti.com/lit/ds/symlink/tps54240.pdf">http://www.ti.com/lit/ds/symlink/tps54240.pdf</a><br />
<br />
IC49 - TPS73801 1.0-A Low-Noise Fast-Transient-Response Low-Dropout Regulator - regulates the +14.5V rail.<br />
<a href="http://www.ti.com/lit/ds/symlink/tps73801.pdf">http://www.ti.com/lit/ds/symlink/tps73801.pdf</a><br />
<br />
IC50 - CD4011 - Quad 2 Input NAND gate<br />
<a href="https://www.ti.com/lit/ds/symlink/cd4011b.pdf">https://www.ti.com/lit/ds/symlink/cd4011b.pdf</a><br />
<br />
IC 53 - TPS7A340 1–20-V, –200-mA,Low-Noise Negative Voltage Regulator - regulates the -14.5V rail.<br />
<a href="http://www.ti.com/lit/ds/symlink/tps7a3401.pdf">http://www.ti.com/lit/ds/symlink/tps7a3401.pdf</a><br />
<br />
DT1 - DT4 - 2DTC114 digital transistors, marked "24" - used in other Korgs.<br />
<a href="https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e">https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e</a><br />
<br />
PC1 - Toshiba TLP2368 Optoisolator - isolates the MIDI input. <br />
<a href="https://www.kynix.com/Detail/697092/TLP285GB.html">https://www.kynix.com/Detail/697092/TLP285GB.html</a><br />
<br />
<h2>
Analog Board (KLM-3162C):</h2>
<br />
I also wanted to fix the headphone output, if possible.<br />
<br />
The analog guts are all on one large PCB that has all the pots and jacks mounted. The jacks and pots are not actually panel mounted with nuts, they just poke through the panel. This does not give the greatest tactile response - everything wobbles a little bit - but it probably explains how Korg managed to keep the price so low. There is at least a large sheet metal cover to stiffen the PCB.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQL0RcBBGpkbhywpHcDF2HeSZExPS_PENalUoRruuc5OsdXcP1ybQfDiJJ7zFHr5xW-5YlJsBmTFwt07E_DW6yKt-pPM8sX3-o_yxFbNjKjmuU3gnhzZiLXt12NIk8MBtQrBvAIxhTGLBK/s1600/analog_board_shield.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="571" data-original-width="1600" height="142" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQL0RcBBGpkbhywpHcDF2HeSZExPS_PENalUoRruuc5OsdXcP1ybQfDiJJ7zFHr5xW-5YlJsBmTFwt07E_DW6yKt-pPM8sX3-o_yxFbNjKjmuU3gnhzZiLXt12NIk8MBtQrBvAIxhTGLBK/s400/analog_board_shield.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">KLM-3162C with shield</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGwToyFZsBIKgwc91exKE7xUDj88o-4AgadZHbhPlJLAbH3Pwae-BygtFYoag1nix02FrjaZOtyggiyujFjTbQ0KC4ZuWy13qzY_LmtBUqiQealnI650rLyUhZTybdhEDURBXgXot6f80v/s1600/analog_board.jPeG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="595" data-original-width="1600" height="148" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGwToyFZsBIKgwc91exKE7xUDj88o-4AgadZHbhPlJLAbH3Pwae-BygtFYoag1nix02FrjaZOtyggiyujFjTbQ0KC4ZuWy13qzY_LmtBUqiQealnI650rLyUhZTybdhEDURBXgXot6f80v/s400/analog_board.jPeG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">KLM-3162C uncovered</td></tr>
</tbody></table>
<br />
The headphone output is in the upper right. The original MS-20 has a very simple headphone amplifier, just an opamp driving each side. The Mini is pretty different, and seems to add transistors to buffer the opamp outputs.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5jnpW1JECpD8UZUI1CFfHk6w0Sjfwd9PwsqcTOTl12mjUkxYUNTcu8ccMCTwW_2pwoCZFcGsJZOJCEQ__YSc0Gfs5co3xP-ZLP5OUdLdbRUncdfztO5FlC03jBNX02gDGswN9GTbCFCEz/s1600/IMG_1610.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5jnpW1JECpD8UZUI1CFfHk6w0Sjfwd9PwsqcTOTl12mjUkxYUNTcu8ccMCTwW_2pwoCZFcGsJZOJCEQ__YSc0Gfs5co3xP-ZLP5OUdLdbRUncdfztO5FlC03jBNX02gDGswN9GTbCFCEz/s400/IMG_1610.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Headphone output circuit. C251 was removed for testing and later repopulated.</td></tr>
</tbody></table>
<br />
I held down some keys and probed around for a signal. The headphone output seemed to disappear at one side of a 10 ohm resistor (R314 & R315) for both left and right outputs. I desoldered these and they confirmed they were open circuits. I replaced them with new 0603 10 ohm parts and the headphone worked. It's possible these were killed by someone patching the headphone jack into somewhere strange and pulling too much current (?)<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDnNtY037xkZldfVtwlwwQo5oXfuPFlv5UmTLW_d-7ik6l1y6HqDs2vVoYh0DP7x6Ij0dG49thr8v28kBxZmu_Cwe5KMFmq6zMI3Pj9tvkvlu-rAWArj3yOwqUY5_PPsCBucY2G4bekRkA/s1600/dead_resistors.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1103" data-original-width="1600" height="220" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDnNtY037xkZldfVtwlwwQo5oXfuPFlv5UmTLW_d-7ik6l1y6HqDs2vVoYh0DP7x6Ij0dG49thr8v28kBxZmu_Cwe5KMFmq6zMI3Pj9tvkvlu-rAWArj3yOwqUY5_PPsCBucY2G4bekRkA/s320/dead_resistors.jpeg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Offending 10 ohm resistors</td></tr>
</tbody></table>
<br />
<h2>
Korg Service Manuals:</h2>
There are a lot of Korg schematics and service manuals online. Many are publically accessible on the Korgusa.com portal, even though the page requires a dealer or repair center account. I used some of the following as reference material:<br />
<br />
MS20 Original service Manual<br />
<a href="http://www.synfo.nl/servicemanuals/Korg/MS-20_SERVICE_MANUAL.pdf">http://www.synfo.nl/servicemanuals/Korg/MS-20_SERVICE_MANUAL.pdf</a><br />
<br />
MicroKorg Service Manual<br />
<a href="https://elektrotanya.com/korg_microkorg_x-1110.pdf/download.html">https://elektrotanya.com/korg_microkorg_x-1110.pdf/download.html</a><br />
<br />
MicroKorg XL Service Manual<br />
<a href="http://dealers.korgusa.com/svcfiles/MKXL_SManual.pdf">http://dealers.korgusa.com/svcfiles/MKXL_SManual.pdf</a><br />
<br />
Korg Kronos Service Manual<br />
<a href="http://www.markpenny.ie/wp-content/uploads/2017/03/273600278-Korg-KRONOS-Service-Manual-v2-0-2012.pdf">http://www.markpenny.ie/wp-content/uploads/2017/03/273600278-Korg-KRONOS-Service-Manual-v2-0-2012.pdf</a><br />
<br />
Korg Volca Bass Service Manual:<br />
<a href="http://www.ksadhu.niezba.org/sajty/korg_volca_bass_sm.pdf">http://www.ksadhu.niezba.org/sajty/korg_volca_bass_sm.pdf</a><br />
<br />
Monotribe schematic:<br />
<a href="https://www.korg.com/download/global/monotribe_schematic/monotribe_sch.pdf">https://www.korg.com/download/global/monotribe_schematic/monotribe_sch.pdf</a><br />
<br />
Monotron delay schematic:<br />
<a href="https://www.korg.com/download/global/monotron_delay_schematic/monotron_DELAY_sch.pdf">https://www.korg.com/download/global/monotron_delay_schematic/monotron_DELAY_sch.pdf</a>krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com7tag:blogger.com,1999:blog-942832708593410658.post-53272355342167292472019-02-14T21:59:00.005+00:002022-10-05T15:25:42.064+01:00Another Ibanez ES2 Echo Shifter repairI took another look at an <a href="https://falseelectronics.blogspot.com/search/label/ES2">Ibanez Echo Shifter</a> that I had previously repaired, but had come back to me. This time it wouldn't light up, but did pass a clean signal. I suspected a bad power supply for the digital section.<br />
<br />
I opened it up, and I could see ~8.5V volts powering the opamps but no voltage at any of the digital parts, where I would expect 3.3V.<br />
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Way back in July 2017 a <a href="https://falseelectronics.blogspot.com/2016/09/ibanez-es2-echo-shifter.html?showComment=1499959302998#c1699497661396665877">commenter asked</a> if I knew what the part number for U14 was, likely to be a buck-converter, and that they suspected it was a <a href="http://www.ti.com/product/TPS62056">Texas Instruments TPS62056</a>. The package, function and chips marking all looked like a perfect match so I ordered a few this week to see if it was right.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzLT6TsY6IkD7V8CQ9CfZL9gKly6Ke8N4rfhaYRPl0GXZEDQEFD_uVGKhWbaGobTwWyM6J3si1xeUS_VIvJ7eZoAAc_WxG_P7jSEC3BMQktfN5SqgwkjfTwOknb0O4lYnU1GBKwCehOhD3/s1600/IMG_1592.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzLT6TsY6IkD7V8CQ9CfZL9gKly6Ke8N4rfhaYRPl0GXZEDQEFD_uVGKhWbaGobTwWyM6J3si1xeUS_VIvJ7eZoAAc_WxG_P7jSEC3BMQktfN5SqgwkjfTwOknb0O4lYnU1GBKwCehOhD3/s400/IMG_1592.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Before</td></tr>
</tbody></table>
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Desoldering was straight-forward, I used hot air and kapton for protecting parts I didn't want to overheat.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKayon03YUegYu_FNdO9WBMaU7L8xtiWqSDUckGWwsoLrqdLiF0B5dbaECE9aijp5lven9eP1iQf6_r7kfuDgyitk9utpIgYgPe8lalIS-LSmzBIT3taRL8o6DlKz0W6ZtM49o7tjuBEA-/s1600/IMG_1593.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKayon03YUegYu_FNdO9WBMaU7L8xtiWqSDUckGWwsoLrqdLiF0B5dbaECE9aijp5lven9eP1iQf6_r7kfuDgyitk9utpIgYgPe8lalIS-LSmzBIT3taRL8o6DlKz0W6ZtM49o7tjuBEA-/s400/IMG_1593.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">During</td></tr>
</tbody></table>
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The new chip has near identical markings to the old one. Re-soldering was a little harder as there isn't a lot of space, I ended up removing C73 temporarily to get better access. The bridged pins are fine, all those pins are connected together at the PCB.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIerd8KH6Gke32nbRWKdFvfheW31xP8pNaGME52YtsiglhUOo_SPyJYBpT15r8WmtXEwIWGLbYsyd3O7Tjf4FSTHPH3iM1oEENUuV7Ece0h-EryEJZyyeZzafuZsiiGNfrAn92D965nGgV/s1600/IMG_1594.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIerd8KH6Gke32nbRWKdFvfheW31xP8pNaGME52YtsiglhUOo_SPyJYBpT15r8WmtXEwIWGLbYsyd3O7Tjf4FSTHPH3iM1oEENUuV7Ece0h-EryEJZyyeZzafuZsiiGNfrAn92D965nGgV/s400/IMG_1594.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">After</td></tr>
</tbody></table>
<br />
Everything works again with the new chip. Thanks to Shane Bussiere for doing the research and sharing the part number, sorry I didn't help out.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1AAfzO7a0WrAOvZTeAPpIKAfyxk362h6O1yt7M4l9YAwK5zEAVI4Q5WTixED7gILmn7X7bozUCPJ9Wn8DstifUv7fH5lyGRMPz6K0CqBduWX7O7yjYx9NS9WkaZrJn5-TEzlaavk3zHJL/s1600/IMG_1595.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1AAfzO7a0WrAOvZTeAPpIKAfyxk362h6O1yt7M4l9YAwK5zEAVI4Q5WTixED7gILmn7X7bozUCPJ9Wn8DstifUv7fH5lyGRMPz6K0CqBduWX7O7yjYx9NS9WkaZrJn5-TEzlaavk3zHJL/s400/IMG_1595.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All working again.</td></tr>
</tbody></table>
<br />
Looking at the <a href="http://www.ti.com/lit/ds/symlink/tps62056.pdf">TPS62056</a> datasheet, I can guess why this failed. The buck converter chip has a maximum Vin of 10V, the Echo Shifter runs the power jack through a series Schottky diode for polarity protection and then to the TPS. If you use a 9V power supply the chip gets around 8.6V, which is fine, but using a 12V power supply or higher will probably kill it. I couldn't find a compatible chip from TI with the same footprint and pinout but higher maximum input voltage, let me know if one exists.<br />
<br />
I would really like to modify this to add a modulation rate control. I hunted around for modulation signals and unfortunately there doesn't seem to be a LFO onboard, it looks like the modulation is done in software in the <a href="https://www.analog.com/en/products/adau1701.html">ADAU1701</a> DSP. A modulated square wave is run out of the first audio DAC on pin 46.<br />
<br />
While I had this open I desoldered the <a href="https://www.microchip.com/wwwproducts/en/24AA128">24AA128</a> serial EEPROM and dumped the contents, it can <a href="https://drive.google.com/file/d/1HRqzytm-v8yFSNC-N_23zqeaY8-UoyiJ/view?usp=sharing">be downloaded here</a>. Afaik the ADAU1701 instruction set is not publicly documented, so I don't think the firmware can be easily modified.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com8tag:blogger.com,1999:blog-942832708593410658.post-59862914656894696382019-02-08T17:40:00.000+00:002019-02-08T17:40:42.852+00:002 70s Electro-Harmonic Small Stone phasers<div class="separator" style="clear: both; text-align: center;">
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2 vintage Electro-Harmonix Small stone phasers. The artwork for both of these is almost identical to the 90s reissue (which uses LM13700 OTAs) but the lack of any LED indicators gives away that these are older - probably late 70s or 80s.<br />
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<img border="0" data-original-height="1169" data-original-width="1600" height="291" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9RsH9eMf2PL36D938RQXjoffzNBrm4JgFZ6nqMovdqPR2jmUXnU6Gdocfz0n2oPwDky1k5wn7k2WEp2Lou73IS6-raybx1ut4W95lSsetsOaUF2QEzVZ4ICEhpWCUlpquK4eL8LdD6xDJ/s400/smallstones.jpeg" width="400" /></div>
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<h2>
Small Stone #1</h2>
I think this is the pedal I have owned the longest with repairing. I started buying broken stuff to repair from eBay in 2011, and picked up a couple of vintage Big Muffs. One was a lot that came with this pedal, a Small Stone, pretty much as pictured - no knob, no pot, no switch and a lot of broken wiring.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPggSqL77l3ffVRzKuV-dvoXfIofEd_SJHFree_knlE4SJDDMs7dIrsQwQ8MBW60NUHLZv3W9YeRUG1X3EpFDW263JHc1TkzUPdXm1KFMJUwNnLvK2tARH_6lHttMpP5xH331o6XNRdyLW/s1600/casing1.JPeG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1176" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPggSqL77l3ffVRzKuV-dvoXfIofEd_SJHFree_knlE4SJDDMs7dIrsQwQ8MBW60NUHLZv3W9YeRUG1X3EpFDW263JHc1TkzUPdXm1KFMJUwNnLvK2tARH_6lHttMpP5xH331o6XNRdyLW/s400/casing1.JPeG" width="293" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiak2248TXjo1z2utca7gcf82OToiGF13seF3KbzWSB1N46KyCKA1aa6VAPj8o9Fp2edIXpacyrGjNFLgRKrt-O5DUGlDrQFRz2NRzfzmREPF0IURkRNw47xmmKc8s3x2hHeFJrgiP13CoZ/s1600/guts1.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1086" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiak2248TXjo1z2utca7gcf82OToiGF13seF3KbzWSB1N46KyCKA1aa6VAPj8o9Fp2edIXpacyrGjNFLgRKrt-O5DUGlDrQFRz2NRzfzmREPF0IURkRNw47xmmKc8s3x2hHeFJrgiP13CoZ/s400/guts1.jpeg" width="271" /></a></div>
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The Small Stone has 4 phase shifting stages, using 1 OTA as an LFO and 4 more as variable RC filters that give varying phase shifts. Early versions of the Small Stone used CA3094 OTAs branded as "EH1048", a house-marking for Electro-Harmonix. This version is an "Issue J" and has the 5 EH1048 chips, dated to 1977.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNeEwpNXKJW3MeX6k681CUhT1KMt3fYujduYoPE08QDT66w-3XC29F-rNQoT_gvBVXuNEfqUqHOacyzVCYV_0KZrGTVOrnrRxaVGFlFjisDAcQMcMJ770RbVdnGBpVtBiPoDMsmCChsZI4/s1600/pcb_1_before.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1199" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNeEwpNXKJW3MeX6k681CUhT1KMt3fYujduYoPE08QDT66w-3XC29F-rNQoT_gvBVXuNEfqUqHOacyzVCYV_0KZrGTVOrnrRxaVGFlFjisDAcQMcMJ770RbVdnGBpVtBiPoDMsmCChsZI4/s400/pcb_1_before.jpeg" width="298" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Issue J</td></tr>
</tbody></table>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs5Ayr4I8V_cWHcVw0kyTGoLRwLGChIbuWszszvE-pzMWWKRhe2bHtSko9NZXT8bqiUrhsfQrYdOK5m-OuPs4N2PrIA-nhTTkyr8htgnI2nuEQkcAly-LV8KafUIXglDp5uMyPhfgR8VGj/s1600/IMG_0763.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs5Ayr4I8V_cWHcVw0kyTGoLRwLGChIbuWszszvE-pzMWWKRhe2bHtSko9NZXT8bqiUrhsfQrYdOK5m-OuPs4N2PrIA-nhTTkyr8htgnI2nuEQkcAly-LV8KafUIXglDp5uMyPhfgR8VGj/s400/IMG_0763.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">EH1048 - 1977, week 32.</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
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<br />
<br />
<br />
I bought a new 24mm reverse log pot, installed a 3PDT switch and re-wired the pedal (true bypass, why not). It didn't pass an effected signal. I think I put it aside at this point, I suspected that the OTAs might be bad and didn't have any replacements.<br />
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<br />
I came back to this recently. The oscilloscope showed that there was no LFO signal anywhere on the board, even though most of the voltages on oscillator OTA looked reasonable. I bought an RCA metal can CA3094 and replaced it - now I had an LFO, but still no wet signal. Looking at the input and output pins of each OTA, I could see that the first stage was phase shifting, but the second had no output. I shorted together the input and outputs of the second stage, and now I had a phase-shifted signal. It wasn't quite as deep as it should be, with only 3 or 4 stages active, but it verified that the other two ICs were good. I ordered one more CA3094 to replace the dead EH1048, and complete things.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhG4mZ0-7F9B0TKZ_zIe99Uqp6JDBID1MaKfHU3f2BeLCnahUIM0qkJT5wQgos-FoBO6RQi_UolDsFtLNqysikvExtPvLgGZvF_P0h1On1yqauo2L5LlDwW_8IBoE6brgR9til4DXAwiXE5/s1600/pcb_1_after.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1053" data-original-width="1600" height="262" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhG4mZ0-7F9B0TKZ_zIe99Uqp6JDBID1MaKfHU3f2BeLCnahUIM0qkJT5wQgos-FoBO6RQi_UolDsFtLNqysikvExtPvLgGZvF_P0h1On1yqauo2L5LlDwW_8IBoE6brgR9til4DXAwiXE5/s400/pcb_1_after.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Before re-housing</td></tr>
</tbody></table>
I sourced a new hockey put knob that fit the new 24mm pot. Originals are hard to come by, but it fits the right aesthetic.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgebKI2uO0KON_YYXcfOxNy_IeJKxIXOCM4JlD5L8adrt4RMyqEEhs5GTDP7Ra3BxTtmj7LZC9SI5R8Eqsxb7F1BtYVm5eJNcTu4WIfosGMKgBpINnacVyCLlJeK9QsaQ66s0JswayTH7_z/s1600/IMG_0765.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgebKI2uO0KON_YYXcfOxNy_IeJKxIXOCM4JlD5L8adrt4RMyqEEhs5GTDP7Ra3BxTtmj7LZC9SI5R8Eqsxb7F1BtYVm5eJNcTu4WIfosGMKgBpINnacVyCLlJeK9QsaQ66s0JswayTH7_z/s400/IMG_0765.JPG" width="400" /></a></div>
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This was inspected by... Elsa? Cheers, Elsa.<br />
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There is usually some foam behind the PCB on the back panel of the housing. The PCBs just hang off the back of the rate pot, the foam is to prevent it from shorting out on the back panel. This foam had perished, so I taped some card down to insulate the PCB instead. <br />
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<h2>
Small Stone #2</h2>
This second unit is a similar vintage, I picked it up hoping it might help repair the first one.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuPnsAqatWQ85y0MEYhPNtIKKuCEnkmF5gxvKR3QT8W2Zly8EXOHF9V7iBR5tisqtO6AjOjmCSx1rBP_Nts-7WZ5_bYeMhNZoxe7uDvnZIE7aNB2Z20VMZN8Ey8Iw7_Ytspn-iGFdIcLcH/s1600/2_pcb.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1219" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuPnsAqatWQ85y0MEYhPNtIKKuCEnkmF5gxvKR3QT8W2Zly8EXOHF9V7iBR5tisqtO6AjOjmCSx1rBP_Nts-7WZ5_bYeMhNZoxe7uDvnZIE7aNB2Z20VMZN8Ey8Iw7_Ytspn-iGFdIcLcH/s400/2_pcb.jpeg" width="303" /></a></div>
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This is a slightly different PCB (with a phenolic substrate instead of fibreglass?), but looks to be the same circuit more-or-less. It also has 5 EH1048s, dated to 1979.<br />
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This one actually worked despite being sold as faulty (this is not that unusual). It just had a couple of quirks. It was a big help in verifying the switch wiring on the other unit, and for taking reference voltage readings off the OTA chips.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzMkvEhBwifdvCpciiOAzlqC_O_g0rKwoKkH-kEXW0xuXWXV646kAm_QSOWsRoIQ20eG68keWO1ufVIG7rBc0kwf0quhDug7yWUURsW8nYBj3JMQClpiGv6rGO_k_BPTjwbAiZOCQ7U7SV/s1600/IMG_1561.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzMkvEhBwifdvCpciiOAzlqC_O_g0rKwoKkH-kEXW0xuXWXV646kAm_QSOWsRoIQ20eG68keWO1ufVIG7rBc0kwf0quhDug7yWUURsW8nYBj3JMQClpiGv6rGO_k_BPTjwbAiZOCQ7U7SV/s400/IMG_1561.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Phenolic PCB, instead of fibreglass?</td></tr>
</tbody></table>
The first was that the rate pot had some odd damage, the casing was partially open. I guess this could have been caused by dropping the pedal onto the knob, or by pulling on the PCB while it was still attached to the enclosure. Or during factory assembly, this was EHX after all. This was easy to close and re-crimp with pliers.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWsvp_HOluRFSaE5YbTNjb_7DK9GNfoILsmqufCutW16Y5bY4ItcNBG3L-MjzWilMdSS6f11DV1sDCHYIo-in_ewxf9iTn8cXd90WTb-ThUwGPFfSKGjtEU42HQV11vg5qhgQeh2kpxI4b/s1600/IMG_1562.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWsvp_HOluRFSaE5YbTNjb_7DK9GNfoILsmqufCutW16Y5bY4ItcNBG3L-MjzWilMdSS6f11DV1sDCHYIo-in_ewxf9iTn8cXd90WTb-ThUwGPFfSKGjtEU42HQV11vg5qhgQeh2kpxI4b/s320/IMG_1562.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Opened pot housing...</td></tr>
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<tr><td class="tr-caption" style="text-align: center;">...closed again</td></tr>
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The second was that it would start to oscillate with the "color" switch in the up position and <i>no input</i>. It works fine with a guitar connected, or a buffered pedal in front of it, but with no cable or dangling unconnected cable it will start to ring at the top of the phaser sweep. As far as I can tell this is just something that this revision does, to fix it I would have to switch to a shorting input jack or modify the pedal to reduce the positive feedback when the color switch is in the up position, neither of which I really want to do.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3wDDc6ebCx_q9eji7rtZCatUCa0XJrrd1oljTVxSLixpIfLBkjT2RY3ZFwtK2Dk1LU0GYPNL8Yo7cwudzrgQZ7XD4qv2G2OXELNqGUgPpal5gCRA5NSo25UfYCLJSyhRwPJhhi1qW8wCm/s1600/IMG_20190207_163055556.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3wDDc6ebCx_q9eji7rtZCatUCa0XJrrd1oljTVxSLixpIfLBkjT2RY3ZFwtK2Dk1LU0GYPNL8Yo7cwudzrgQZ7XD4qv2G2OXELNqGUgPpal5gCRA5NSo25UfYCLJSyhRwPJhhi1qW8wCm/s400/IMG_20190207_163055556.jpg" width="400" /></a></div>
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These turned out really well. Feels good to have them done. They sound almost identical, the only change that jumps out is that the two different brands of pots don't quite match up - the plastic shaft CTS pot physically rotates further than the new Alpha pot, so the rates are slightly different when the pointers are matched by eye.<br />
I don't have a modern Small Stone, or a Sovtek, to compare with. They definitely sound smoother than JFET phasers I'm used to.<br />
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One or both of these will probably hit Reverb in the next couple of days, get in touch if interested.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com7tag:blogger.com,1999:blog-942832708593410658.post-33099001054768809302019-02-08T14:18:00.002+00:002019-02-08T16:02:35.524+00:00Electro-Harmonix Stereo Memory Man (EH-7811)The classic, basic, no-frills BBD delay. This is an EH-7811 revision, dating from around 1980 based on IC codes. This version is main powered (240V), runs at +/-15V internally, Panasonic MN3005. There is no LED, I think this was the last version without one. There is an Echo/Chorus switch which probably reduces delay times, and in-phase and out-of-phase outputs for a "stereo" effect.<br />
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This is another one that I have had a for a while, and later came back to. I bought this a couple of years ago and nearly got it working, then hit a dead-end.<br />
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It was pretty dirty on first inspection, and missing a knob for the blend control. The power cable had been shortened to a ridiculous length, about six inches, making it awkward to work on.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhN6jL19Mya5u6LJ5IpahDZhWWw0DkccCjsvXfMirpQxHv5KiEnGmkTiKjTuxuGvlQYCansb9S72PKuCk7TUbM76ix9ZM0hEXbTRVvK0kEBQdnBFNXh5YZ-7fbb5J5Ywwneh_re876TzGiy/s1600/cropped.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1266" data-original-width="1600" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhN6jL19Mya5u6LJ5IpahDZhWWw0DkccCjsvXfMirpQxHv5KiEnGmkTiKjTuxuGvlQYCansb9S72PKuCk7TUbM76ix9ZM0hEXbTRVvK0kEBQdnBFNXh5YZ-7fbb5J5Ywwneh_re876TzGiy/s400/cropped.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Before cleaning...</td></tr>
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The original eBay picture shows this off:</div>
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<img border="0" data-original-height="200" data-original-width="125" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCkzhBn2xXLqEmmwDsF0HccydX8YRFOhDYl2mWz6tkkTduZr_TiaLpz4oxFha-J0wATJjh0vDe8TS3CVeiRUKSRFPiusYwrecAYuI_ktYtiyJm5uWh8K_kesuRKEzZ-AFWku4ic8OSJ_af/s1600/unnamed.jpg" /> </div>
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The insides show that the PCB is complete with no obvious damage. It does anchor everything off of board-mounted pots which are only on one side of the large PCB - the other end floats and tends to cantilever.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiibKVV9Wuzuw1kOY6I0lzY9vYDGY3qlY8-pKmVsBJ36-Tg3rB-7P-nqqIzGYoq67DbatC6tV2-EXsbxTInlg_cqmbqAhZY0SvqzTpdT7HGd8ui9OhyFnyNdxlzxmqtCvHfMQxv6FwV6_SS/s1600/IMG_0932.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiibKVV9Wuzuw1kOY6I0lzY9vYDGY3qlY8-pKmVsBJ36-Tg3rB-7P-nqqIzGYoq67DbatC6tV2-EXsbxTInlg_cqmbqAhZY0SvqzTpdT7HGd8ui9OhyFnyNdxlzxmqtCvHfMQxv6FwV6_SS/s400/IMG_0932.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PCB as received</td></tr>
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The delay/chorus switch is almost entirely missing, just the frame left.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvYbuQv3JV5ZPntMNb2QMvvPPGt-AOm4TFxXcKUABJatIVtCkJiiKf0t02aZgaIREuSWeBZikKiX13c8AOoVVNakWVP73y-VCloCAEFkunhf18YgX1QOvNZHG81hrIf1A52TtbTuXGW0mn/s1600/IMG_0934.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvYbuQv3JV5ZPntMNb2QMvvPPGt-AOm4TFxXcKUABJatIVtCkJiiKf0t02aZgaIREuSWeBZikKiX13c8AOoVVNakWVP73y-VCloCAEFkunhf18YgX1QOvNZHG81hrIf1A52TtbTuXGW0mn/s400/IMG_0934.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Interior of case, Echo/Chorus switch.</td></tr>
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Closer inspection of the PCB found that the Blend potentiometer's pads had all craclked off. The pot was still hanging onto the board, but nothing was electrically connected. I ran some small jumpers from the pot back to the nearby traces. I also installed a new sliding switch. I referenced a schematic for the later EH-7811B at <a href="https://sites.google.com/a/davidmorrin.com/www/home/trouble/troubleeffects/electro-harmonix-memory-man/eh-7811b">David Morrin's excellent site</a>. The main difference (apart from the LED) seems to be that this version has an extra 741 opamp to invert the delay signal for the out-of-phase output.</div>
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At this point, I had some signal coming thorough, but hugely distorted. All output opamps were saturated, sitting at ~ 13 or -13 volts. I socketed and replaced some of the opamps with no change. There was a DC offset being introduced somewhere.</div>
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I had a few ideas:</div>
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<li>dead opamp, or opamp feedback network. No changes when swapping opamps and measuring feedback resistors.</li>
<li>leaking AC-coupling capacitors. I replaced some 1uF caps of a type I had seen fail before with modern film caps, no changes</li>
<li>Missing ground node somewhere...</li>
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This went back into the "fix later" box for a while. I dug it out and went over some of schematics for other revisions and noticed that one side of the blend knob should be connected to ground. My blend knob had been cracked off the board, I could barely see a small track below the pot's pads that should have been connecting to ground.<br />
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I ran another jumper wire to ground, and now all the outputs were sitting at 0V. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6KeVuLNvYHzIfQFCuC_AUrAALX-yVbAAtxrZDEj16yHxaHIHkKlfzvofKIloL3UCHQzyKLg8FRR0wgt7LyUlv3RKQZeTWY_RVCVtWF2h3sHyokCH0UbM1kraa18hDh9UD0sLua1lWd1r3/s1600/stereo_memory_man.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1237" data-original-width="1600" height="492" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6KeVuLNvYHzIfQFCuC_AUrAALX-yVbAAtxrZDEj16yHxaHIHkKlfzvofKIloL3UCHQzyKLg8FRR0wgt7LyUlv3RKQZeTWY_RVCVtWF2h3sHyokCH0UbM1kraa18hDh9UD0sLua1lWd1r3/s640/stereo_memory_man.png" width="640" /></a> </div>
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I fitted a new mains cable so that is actually usable. There is no internal fuse, so I changed the cable fuse to a 3A part. I tried the original opamps in the sockets, but the outputs got noticeably more noisy. Maybe semiconductor processing has improved to the point where new 4558s and 741s are less hiss-y.<br />
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There was some serious clock whine, especially at long delay times. Fortunately I was able to completely trim this out. <br />
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<tr><td class="tr-caption" style="text-align: center;">PCB after repairs.</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeGIlKf6gVvIYEHZZEXXpZ-Hpmk6hSFHhHO_8uPliWZY8JIjU0GHHYtE4sUcpGmooDxWTXZT9pSR3nj7vZgDnOzfML-wiMKR6VmmroQoIBTc-yAuG1GcqgiYE2PRz0HSJKlMf-sY5rwemA/s1600/IMG_1524.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeGIlKf6gVvIYEHZZEXXpZ-Hpmk6hSFHhHO_8uPliWZY8JIjU0GHHYtE4sUcpGmooDxWTXZT9pSR3nj7vZgDnOzfML-wiMKR6VmmroQoIBTc-yAuG1GcqgiYE2PRz0HSJKlMf-sY5rwemA/s400/IMG_1524.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PCB after repairs, parts replacement.</td></tr>
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I've said before I haven't noticed huge differences between analog delays based on BBD types. I had the <a href="https://falseelectronics.blogspot.com/2019/01/way-huge-aqua-puss-mk-ii.html">Aqua Puss</a> at hand for comparison between a V3205 and MN3005. The Memory Man sounds cleaner, if that makes sense? Less distortion on each repeat, a bit closer to the original signal. Still sounds like analog delay, just not as overblown.</div>
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<tr><td class="tr-caption" style="text-align: center;">Reassembled.</td></tr>
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krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com4tag:blogger.com,1999:blog-942832708593410658.post-28151435829595468712019-02-04T22:10:00.002+00:002019-02-04T22:10:39.484+00:00Digitech PDS 1700 Chorus/FlangerI picked this up out of curiosity, I'm fond of the <a href="http://falseelectronics.blogspot.com/2017/11/digitech-pds-1000-2000-repairs.html">PDS series</a> and the off-the-shelf design. This is a digital Chorus and Flanger, where the traditional BBD design has been replaced with an 8-bit digital delay line (i.e. not DSP or modelling) and the delayed signal mixed in the analog domain. This one worked but didn't switch very well. <br />
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<tr><td class="tr-caption" style="text-align: center;">PDS 1700</td></tr>
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There aren't too many surprises when comparing the insides to the <a href="http://falseelectronics.blogspot.com/2017/11/digitech-pds-1000-2000-repairs.html">PDS delays</a>. There is the same ADC (<a href="http://www.ti.com/lit/ds/symlink/adc0820-n.pdf">ADC0820)</a> but instead of DRAM it uses a single 2k 6116 SRAM. This is probably because the required delay times for a Chorus and Flanger are much shorter (this pedal maxes out at 51 ms) they could spring for the more expensive SRAM. This also means all the DRAM refresh circuitry isn't needed, and there are fewer logic chips overall.<br />
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<tr><td class="tr-caption" style="text-align: center;">Guts</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj_Q_0b7kWpa4WU660gj81uR5jLNWtF-FBE0VhyYIq7PqP2FK2LNLwkLokK2rsh5ywT-pNr8-uhQb0OEuE7my4OM2t_NXBZCtJvQrUSsOJSlW6kMvB_C-pSWmkPacWFUNo9LCEJhE8HMxc/s1600/backside.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1324" data-original-width="1600" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj_Q_0b7kWpa4WU660gj81uR5jLNWtF-FBE0VhyYIq7PqP2FK2LNLwkLokK2rsh5ywT-pNr8-uhQb0OEuE7my4OM2t_NXBZCtJvQrUSsOJSlW6kMvB_C-pSWmkPacWFUNo9LCEJhE8HMxc/s400/backside.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PCB Backside</td></tr>
</tbody></table>
<br />
The switches were pretty flaky. The mechanical design DOD/Digitech used at the time has a poor reputation for reliability. I find that if they are maintained they work well, but I don't think they stand up to force. The classic problem is that switches that won't switch on the first try get a harder stomp the second time, and things deteriorate.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgH30alLZNgONcJ2v7aa8yCowr7kHbNtHVCx64XVyKWPu11ceg9hP4bn3sFPczIeZ3AeTZqeEuHqCdYRDiAYuL9DsT6cWIgA9tq604nocj9egPwCmMfjbMqmDCCDV8lJjRvOmtCz0mQ65qz/s1600/hardware.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1280" data-original-width="1600" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgH30alLZNgONcJ2v7aa8yCowr7kHbNtHVCx64XVyKWPu11ceg9hP4bn3sFPczIeZ3AeTZqeEuHqCdYRDiAYuL9DsT6cWIgA9tq604nocj9egPwCmMfjbMqmDCCDV8lJjRvOmtCz0mQ65qz/s400/hardware.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PDS hardware. Input jack looks non-original.</td></tr>
</tbody></table>
The paddles press down on momentary push buttons on PCBs inside the pedal. The paddles bear against two bolts that pass through slightly oversized holes in the enclosure. There is a preloaded spring on the bolts on the insides to push them against the enclosure, with nuts holding the springs under tension. There is another return spring on the switch PCB to bounce the paddle back.<br />
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I replaced the switches, I'm using <a href="https://ie.farnell.com/multicomp/mcdts2-1r/tactile-switch-4-3mm-260g/dp/9471669?MER=sy-me-pd-mi-alte">these</a>. There was some play in the paddles, the bypass one would rotate slightly in place, meaning it would not always hit the button switch. I tightened down the nuts on the inside until this play was removed, then it switched every time. You need a 3/32" hex key and a 1/4" socket wrench to make the adjustment.<br />
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The effects are cool. There is interesting play between the delay time and depth controls, the flanger side can go from covering high to lower-frequency ranges, kind of like the difference between a Boss BF-2 and a HF-2. The chorus does odd (cool) detuning effects at high delay times, modulated chorus in the middle and traditional chorus at minimum delay.<br />
<br />
I have <a href="https://reverb.com/uk/item/18833753-digitech-pds1700-digital-stereo-chorus-flanger-boss-style-dc-adapter-included">this one listed on Reverb</a> if anyone is interested.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com3tag:blogger.com,1999:blog-942832708593410658.post-87005596551228689502019-01-31T16:11:00.002+00:002019-01-31T16:11:46.813+00:00Another Electro-Harmonix FreezeI got another Electro-Harmonix Freeze fairly cheap, it sounded like it had been killed by an incorrect wrong power supply. I took it apart and found that it was a newer revision than <a href="http://falseelectronics.blogspot.com/2017/06/electro-harmonix-freeze.html">I had seen before,</a> the board was EC-D68 Rev C (the last one was Rev B). The main difference I notice was an AK4558 codec instead of PCM3052A.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF17LyUQacnxsAUuOyy0Z_fBguOoNg8s6DNIGMOqB_i_sSQQ1kQ-MkYRQfxeL2g_zS8lNRikoK8H4-OjuMIUUWFObvkgF3PYiI8IhDCtIZKuoBOUGAJLlMO1HwRPIN4ve4ZeVK2g8kEQmG/s1600/IMG_1505.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF17LyUQacnxsAUuOyy0Z_fBguOoNg8s6DNIGMOqB_i_sSQQ1kQ-MkYRQfxeL2g_zS8lNRikoK8H4-OjuMIUUWFObvkgF3PYiI8IhDCtIZKuoBOUGAJLlMO1HwRPIN4ve4ZeVK2g8kEQmG/s400/IMG_1505.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Freeze Rev C PCB, flash ROM temporarily removed.</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0IDmn39CT8jRZ17xHxjwwgb8OqUf6NvHLMMalgO9cOkx4RR7PvnwM3nvNO8MMP0BLGwPprM8uaYR63FYjeicaSDb0mca5Kz3LZgycw720rYGMk4Lf0Ep0ZAjkRhufOsS2lN9EoLGAHbtK/s1600/pcb_main.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1408" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0IDmn39CT8jRZ17xHxjwwgb8OqUf6NvHLMMalgO9cOkx4RR7PvnwM3nvNO8MMP0BLGwPprM8uaYR63FYjeicaSDb0mca5Kz3LZgycw720rYGMk4Lf0Ep0ZAjkRhufOsS2lN9EoLGAHbtK/s400/pcb_main.JPG" width="351" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Main PCB, LM317 temporarily removed.</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
There was no sign of life, I found that the series Schottky diode at the 9V input had failed open-circuit and that the LM317 had an internal short between it's input and output pins. The fast/slow/latch mode switch also fell to pieces when the board came out of the enclosure.<br />
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I replaced the bad diode with an SS14L (it was the correct size and I already had some at hand) and installed a new LM317. I thought that the LM317 was supplying 3.3V to the DSP and this would fix everything. Instead, the pedal would pass a clean signal but with a clicking sound once or twice per second. I found out that LM317 is actually used as a 1.25V regulator, which is only used for the analog VCC of the DSP56374.<br />
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I thought the clicking may be the DSP watchdog timer firing, possibly because it was missing program code, so I removed the flash memory and dumped it. It was a perfect match for the dump I made of the first pedal I repaired, so no problem there.<br />
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Measuring power at every IC I found that the 5V rail was high at around 5.9V and the 3.3V supply was sitting at 3.9V. I thought that U5 and U8 (both SOT-89 packages) were also voltage regulators and that maybe they had been damaged as well. I also noticed that U6 is connected to the reset pin of the DSP, and it was resetting the DSP every second or so. My guess is that U6 (also connected to the 3.3V supply) is some kind of voltage supervisor and it is resetting the DSP because of an incorrect 3.9V at VCC.<br />
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I found a great picture at <a href="http://freestompboxes.org/viewtopic.php?f=1&t=9967&hilit=freeze&sid=e1670878f3acd2dd0529cfc55ac6df20">freestompboxes</a> (thanks to Steven_M!) showing that on previous version, U5 was 78L05 (5V regulator) and U8 was BA932 (who knows, but from context it has to be a 3.3V regulator). <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKyIlrJsvj-8-8zMe_kkuOEE4G9L-S9JUaUf2vrJinveR1V391p2PrR3Kc2ddsAj9LIwjqUaH0OXVTg36sx4nEGB0nstl8nOy2OVSz9uCkroQw8EAzLUEfnfDwoJPx_gVeGKshyPZ4M5fn/s1600/DSC_0588.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="553" data-original-width="573" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKyIlrJsvj-8-8zMe_kkuOEE4G9L-S9JUaUf2vrJinveR1V391p2PrR3Kc2ddsAj9LIwjqUaH0OXVTg36sx4nEGB0nstl8nOy2OVSz9uCkroQw8EAzLUEfnfDwoJPx_gVeGKshyPZ4M5fn/s320/DSC_0588.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">U5 & U8 on another revision.</td></tr>
</tbody></table>
<br />
The Rev C board in front of me had "BA420" on <b>both</b> chips. Possibly EHX decided to run all 5V parts off of 3.3V, and doubled up on regulators? I don't know.an<br />
<br />
To test this out, I decided to remove both chips and apply 5V and 3.3V from external power supplies.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgV0SJB0hTTvfxTL61YJzgC1WYrLkmPhuWGKJj4T0HUzaflHts9w7cKjnGY_7o3ueGZGIMio6Ohtr5LS9kiOyV1rrqbqmtJQ6T8Q8PcAHhghfsfjjreuzQK_z77kFXZUA29YLpxdsr_lSIO/s1600/external_power.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1397" data-original-width="1600" height="348" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgV0SJB0hTTvfxTL61YJzgC1WYrLkmPhuWGKJj4T0HUzaflHts9w7cKjnGY_7o3ueGZGIMio6Ohtr5LS9kiOyV1rrqbqmtJQ6T8Q8PcAHhghfsfjjreuzQK_z77kFXZUA29YLpxdsr_lSIO/s400/external_power.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">U5 & U8 removed, external power applied</td></tr>
</tbody></table>
<br />
This set up was a little awkward, but everything work correctly. Current draw looked totally reasonable, 19mA from the 5V supply and 21mA from the 3.3V. No resetting, no clicking, and the pedal could freeze audio in all 3 modes.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcA21s1X7EJcKQuuCk4a8KOuaY9RbXew9a-qLfZcmh9MDCoeU4QbTVT-XtF2F2UoJLuYCTQC-W4oTja91i9oYMfSnMWTt2xiIZMbniDFgTmN8VcFCLC7oK48FyupMUDy_zpj1pz46RrOMu/s1600/IMG_20190117_192329280.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcA21s1X7EJcKQuuCk4a8KOuaY9RbXew9a-qLfZcmh9MDCoeU4QbTVT-XtF2F2UoJLuYCTQC-W4oTja91i9oYMfSnMWTt2xiIZMbniDFgTmN8VcFCLC7oK48FyupMUDy_zpj1pz46RrOMu/s400/IMG_20190117_192329280.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Current draw on 5V and 3.3V supplies.</td></tr>
</tbody></table>
<br />
I ordered <a href="https://uk.farnell.com/stmicroelectronics/l78l05abutr/ic-v-reg-5v-smd/dp/1467762">L78L05ABUTR</a> and <a href="https://uk.farnell.com/microchip/mcp1804t-3302i-mb/ldo-fixed-3-3v-0-15a-sot-89-3/dp/2851553">MCP1804T-3302I/MB</a> as replacement 5V and 3.3V SOT-89 regulators. I also used <a href="https://uk.farnell.com/multicomp/2md3t2b2m2re/switch-pcb-dpdt-vert/dp/9473009">2MD3T2B2M2RE</a> as a replacement switch. This replacement is not threaded for a nut, but recent version of the Freeze don't look like they are threaded either. Pedal works like new.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLk6FZ5i9GuadbYDb7riMB0zatp6vREnEnuQ9EnmqiCorQPEEsmMsrmn1m-cDh8m-FpHcSOVJeYiUOxLbggicVmWBurw5d2dEF15H5P9Vm0sU1nJ59swcY59NXWsa3d7sq40k6z-HvluI5/s1600/IMG_20190131_160402857.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLk6FZ5i9GuadbYDb7riMB0zatp6vREnEnuQ9EnmqiCorQPEEsmMsrmn1m-cDh8m-FpHcSOVJeYiUOxLbggicVmWBurw5d2dEF15H5P9Vm0sU1nJ59swcY59NXWsa3d7sq40k6z-HvluI5/s400/IMG_20190131_160402857.jpg" width="300" /></a></div>
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<br />krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com6tag:blogger.com,1999:blog-942832708593410658.post-83612644028483301112019-01-31T15:12:00.000+00:002019-01-31T15:12:14.220+00:00Ibanez DDL10 Delay IIThis is another early digital delay pedal, I am guessing it was built in 1986 from some of the IC date codes. I don't know if the 10 series included the first Ibanez/Maxon digital delay. Obviously this is the "Delay II", but the DDL Delay I and Delay III were also released in the same series of pedals, each with different delay times. The max delay time of 900ms of the Delay II put it in a similar league to the Boss DD-2.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBaOW7TyjdRdvn_snzC1sj0e9lDx4DGqR4Xgocng2eUHOzVoQfMSIv3F4GLo2MmwneVF2MUgDo8uCa_71dATDYN_qaZPRH2nK0RB_i8T5Zwm9-LsCZ8GAXrEwGCaAbbbVoJ-NAQqPaDXxk/s1600/ddl10.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1087" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBaOW7TyjdRdvn_snzC1sj0e9lDx4DGqR4Xgocng2eUHOzVoQfMSIv3F4GLo2MmwneVF2MUgDo8uCa_71dATDYN_qaZPRH2nK0RB_i8T5Zwm9-LsCZ8GAXrEwGCaAbbbVoJ-NAQqPaDXxk/s400/ddl10.jpeg" width="271" /></a></div>
<br />Inside, there is a two PCB construction with a hard-wired ribbon cable. The top board has unpopulated parts, I would guess that a DML10 (modulated delay) could be built on this same board by populating an opamp LFO and adding the two extra pots.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmuueVk0q-qcyRrq_ZZeknX0ZKqxD1ZqUz2D1VjVopYXBe7UuF89FlnSdDmC5I3L_9ZlHfkGBum0x2oJ2-7ewds8ATJAgHigBJKo53lQw9iWCzzSvobdovToAprKYJBff3o7uqRBBDefGk/s1600/boards.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="972" data-original-width="1600" height="242" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmuueVk0q-qcyRrq_ZZeknX0ZKqxD1ZqUz2D1VjVopYXBe7UuF89FlnSdDmC5I3L_9ZlHfkGBum0x2oJ2-7ewds8ATJAgHigBJKo53lQw9iWCzzSvobdovToAprKYJBff3o7uqRBBDefGk/s400/boards.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DDL10 internals</td></tr>
</tbody></table>
<br />
The bottom PCB has two 4164 DRAMs, an NE571 compoundor, LM311 comparator (most likely used as part of an ADC as in the <a href="http://falseelectronics.blogspot.com/2017/08/boss-dd-2.html">DD-2</a> and <a href="https://falseelectronics.blogspot.com/2017/11/digitech-pds-1000-2000-repairs.html">PDS delays</a>) and a bunch of opamps. The SIL (single in-line) package chips are M5218L low-noise preamplifiers, used in lots of Japanese pedals. There are only 2 4164 64kb DRAMs, the DD-2 has 3. Either the DD-3 has higher sampling rates, or the Ibanez uses 8-bit samples instead of 12-bit. This is still more than the single 64k seen in Digitech PDS 1 second delays.<br /><br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLeuDqBKB8bmC9glZAVzPJootDaEJHNSVYLsO7pePnF1OoUKIzLZn6GUpsW40kLT_O67vt6R4jnUC8E6F5XnPj5u8IlpklNzkaAnXA3wpbSw5V_8zVxGe_RqRobiSSXD3kDyCDr2TiMECJ/s1600/main_board.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1467" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLeuDqBKB8bmC9glZAVzPJootDaEJHNSVYLsO7pePnF1OoUKIzLZn6GUpsW40kLT_O67vt6R4jnUC8E6F5XnPj5u8IlpklNzkaAnXA3wpbSw5V_8zVxGe_RqRobiSSXD3kDyCDr2TiMECJ/s400/main_board.jpeg" width="366" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Main PCB, component side</td></tr>
</tbody></table>
<br />
The back side of the lower board just has a main controller MC4101F IC. I can't find any info on this, it's almost certainly a custom controller for digital delays (like the Boss/Roland RDD63H101).<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqYyRi-JV7obshfLbG5IuiwuIkvWPEnP4wGhyphenhyphenPOjHeFd3CINOOIxjt646elHWs-E9tFITS4yXgaIPfbCOcAIpCKIhoPswIUOAwhWlpRCNQgU_7uorR1bu3xxc-f04gNn8sPNpvKs3IooVH/s1600/IMG_1499.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqYyRi-JV7obshfLbG5IuiwuIkvWPEnP4wGhyphenhyphenPOjHeFd3CINOOIxjt646elHWs-E9tFITS4yXgaIPfbCOcAIpCKIhoPswIUOAwhWlpRCNQgU_7uorR1bu3xxc-f04gNn8sPNpvKs3IooVH/s400/IMG_1499.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Main PCB, back-side.</td></tr>
</tbody></table>
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This unit looked mostly dead, it passed no effected signal and LED didn't respond to the footswitch. I thought the back of the larger board looked a bit crusty so I clean it with 99% IPA, afterwards I saw the LED blink with the footswitch. Still no signal.<br />
<br />
I couldn't find any schematics for this model online, but someone has scanned and uploaded an Ibanez factory schematic for the DFL10 flanger from the same series, which uses the same controller IC. There is a full pinout.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAhM6nnNXJL4EM1nnAJI_ze39Hc8o9RPxH0hvKC6DvqDqPXA3ohP0S3TvNlTKgt4is6JJiDfSWtMAjymDUdyLLZMEOCMCrROq1ZIH9uRu6YNyHY_X6fOdj__StfQDrpx6U62nsICznnsqi/s1600/ibz_DFL2.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1250" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAhM6nnNXJL4EM1nnAJI_ze39Hc8o9RPxH0hvKC6DvqDqPXA3ohP0S3TvNlTKgt4is6JJiDfSWtMAjymDUdyLLZMEOCMCrROq1ZIH9uRu6YNyHY_X6fOdj__StfQDrpx6U62nsICznnsqi/s400/ibz_DFL2.gif" width="311" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DFL10 schematic page 1.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiggSqdVuqJWqhb6guTuW3rTDB_xYXQbYq43ul-VoIUq3YBUFVIxigqRnHkvnu_vHZD_QaUlHGNCkc1pvJ5VRRdfStvltCnWHf76OwKgogJ9wUjgkoQ2CerZYYVN7DGkWmxVP_h9SU3L-Jt/s1600/ibz_DFL1.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1212" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiggSqdVuqJWqhb6guTuW3rTDB_xYXQbYq43ul-VoIUq3YBUFVIxigqRnHkvnu_vHZD_QaUlHGNCkc1pvJ5VRRdfStvltCnWHf76OwKgogJ9wUjgkoQ2CerZYYVN7DGkWmxVP_h9SU3L-Jt/s400/ibz_DFL1.gif" width="302" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DFL10 schematic page 2.</td></tr>
</tbody></table>
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From the schematic, the clock signal for the controller looked like it was coming from a VCO to pin 26 ("2F"). I probed my board and found that I did have a clock signal, it could be varied by turning the Delay knob, and I also had what looked like communication between the controller and the RAM chips.<br />
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At this point I got really lucky. There was a 100uF electrolytic capacitor near the LM311 comparator that was a little discoloured. While taking measurements I noticed it was getting warm. I pulled it from the circuit, and the pedal started passing a delayed signal. This cap is connected from 5V to ground right next to the comparator input, if the cap was leaky then it would effectively mute the comparator. Everything worked without this capacitor, I replaced it anyway with a new low profile 100uF for peace of mind. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7aCOAsf1NPKxi_mfDEmNbq0ejS71Vfqc-bemjiW7OctiP3ldrDyRNHoEKm-T260hJxI5NHj_gGucrTqVw10Zw74liz-yz-9fDrLBfJgpla87x_mnkI1bWC_fvg5zatAIYjzNJIIORZrzg/s1600/pulled_cap.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7aCOAsf1NPKxi_mfDEmNbq0ejS71Vfqc-bemjiW7OctiP3ldrDyRNHoEKm-T260hJxI5NHj_gGucrTqVw10Zw74liz-yz-9fDrLBfJgpla87x_mnkI1bWC_fvg5zatAIYjzNJIIORZrzg/s400/pulled_cap.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Faulty capacitor pulled.</td></tr>
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The LED turned out to be a bad solder joint - it would light sometimes if it was held in a certain position. Reflowing the joints fixed it.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com3tag:blogger.com,1999:blog-942832708593410658.post-72648291662857505472019-01-31T13:22:00.000+00:002019-02-01T11:00:38.085+00:00Way Huge Aqua Puss MK II<div class="separator" style="clear: both; text-align: center;">
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I don't think I've ever looked at anything by Way Huge before. This is a modern version of the Aqua-Puss, and Jim Dunlop acquired Way Huge in 2006, so I expect it to be similar to the current Dunlop and MXR stuff.</div>
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This one would light it's LED when switched on but wouldn't pass a signal.</div>
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<img border="0" data-original-height="1600" data-original-width="1451" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiVCLGrLp866IYEYo11FTKixduyqKdioMyt3lFWBW_o_CaFZHC0a_JAcbldRNVjAXjZ1ldcDp94M7ROeGWmFBKFZ4TfgUJZTk0v8vjDS2OZl8IUWwsPi5sZ92dQrTvL-OvDgu5xeGUawyvh/s400/aqua_puss.jpeg" width="362" /></div>
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The insides are really nice, and very easy to disassemble. There are three PCBs - one just breaking out the switch contacts, one SMD board for input/output and switching and one through-hole board with the effect guts. They probably re-use the two smaller PCBs for all of the pedals in this size of enclosure. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJgJyAqDWXZQlTVq5TyCr5npWsv2ItDz5LjAWejznBIN04xe5IlC-GnWsCnnbo0v_o2nLlPezVJ-_KbI4BNRg9nxcPA42gs3wh1vBd266ZbQgyKpejhGAsFwoDXrA0doSBtpQAKoojZVjD/s1600/guts.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1324" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJgJyAqDWXZQlTVq5TyCr5npWsv2ItDz5LjAWejznBIN04xe5IlC-GnWsCnnbo0v_o2nLlPezVJ-_KbI4BNRg9nxcPA42gs3wh1vBd266ZbQgyKpejhGAsFwoDXrA0doSBtpQAKoojZVjD/s400/guts.jpeg" width="330" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Interior</td></tr>
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The upper board has a CD4013 dual flip-flop, a CD4093B quad NAND gate and a relay to handle the bypass. The manual says the pedal has "AC protection", I don't know if this is just a series Shottky diode or something more sophisticated. There are some opamps and what looks like a <a href="https://www.infineon.com/dgdl/irf7606pbf.pdf?fileId=5546d462533600a401535603bc101c80">IRF7606</a> Mosfet in a micro-8 package, that could be doing some power switching in case of reverse polarity or an AC supply connected. Relay is a EA2-5SNJ, similar to what's in a DL4.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkLEgk29S6ji85OC-cXL_sJApKNOC6D0oW-cVxVL9xgljT5rZ8X-JvsaSd7p0QNuSKXj01DRc-9DACbCGXFgfh4PSr53aVBE3xsmTfLvJSMBlFQ79pFBMYZTl0nkM4HGdJjTc2mIAwTwL4/s1600/ioboard_top.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1333" data-original-width="1600" height="332" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkLEgk29S6ji85OC-cXL_sJApKNOC6D0oW-cVxVL9xgljT5rZ8X-JvsaSd7p0QNuSKXj01DRc-9DACbCGXFgfh4PSr53aVBE3xsmTfLvJSMBlFQ79pFBMYZTl0nkM4HGdJjTc2mIAwTwL4/s400/ioboard_top.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I/O & switching board component side</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDJ9ipxrgQ2S17wJKXS1u905QEXv7UbzXQEpSZMwINx5NK-4T6jrb7giQofWdZxH_r4js8x-0ptc4IrmbOeOAl_Lj9Rxw-HTuOhRosGRt7DPG6UitGcgObmcpS8oJTLy5HLVypae4BQI-T/s1600/ioboard.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1510" data-original-width="1600" height="376" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDJ9ipxrgQ2S17wJKXS1u905QEXv7UbzXQEpSZMwINx5NK-4T6jrb7giQofWdZxH_r4js8x-0ptc4IrmbOeOAl_Lj9Rxw-HTuOhRosGRt7DPG6UitGcgObmcpS8oJTLy5HLVypae4BQI-T/s400/ioboard.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Jack side</td></tr>
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The delay board a V3205 BBD and BL3102 clock generator, SA571 compoundor and LF353 opamp for input and output buffering. <a href="http://www.freestompboxes.org/viewtopic.php?f=7&t=4216&start=540">Freestompboxes.org has the full schematic</a>, it's not too complex a delay and similar to a DM-2/DM-3.<br />
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Pinout of the 8-pin connector is as follows (taking the pin with square PCB footprint as pin 1)<br />
<ol>
<li>9V</li>
<li>Ground</li>
<li>LED</li>
<li>Bypass switch</li>
<li>Input signal</li>
<li>Output signal</li>
<li>Relay coil</li>
<li>Relay coil </li>
</ol>
The relay coil contacts are probably only broken out so the small PCB can be connected to a test jig, the main board doesn't route them anywhere. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7_qKo-uXWeba2ZWQVRRD9yjboJciU4J-We7TDKgRpXo7Ir-8yVX7OTnEjH_veuakPYZ1clJIqXMluMOjtc11OoUergfSMPCOtVKI5n30hcoUzifz3gLeup0W95-OK7RO-9uImYdfw6J3A/s1600/mainboard_top.jpeg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1595" data-original-width="1600" height="398" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7_qKo-uXWeba2ZWQVRRD9yjboJciU4J-We7TDKgRpXo7Ir-8yVX7OTnEjH_veuakPYZ1clJIqXMluMOjtc11OoUergfSMPCOtVKI5n30hcoUzifz3gLeup0W95-OK7RO-9uImYdfw6J3A/s400/mainboard_top.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Delay board component side</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU3ZSx5XZiD-ZXi2fLBe1FHZiw6vx8is3H6oxouZlvTFO1J50tpNbe4fwhcCoUaw6NgN86a8aJ6iD7OLNCHCkhIaXI27V13SmY-l4iwHYiepFLfABDWEpvzUBBu_F-kCL8Z18NHSpj2ywu/s1600/mainboard_back.jPeG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1574" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU3ZSx5XZiD-ZXi2fLBe1FHZiw6vx8is3H6oxouZlvTFO1J50tpNbe4fwhcCoUaw6NgN86a8aJ6iD7OLNCHCkhIaXI27V13SmY-l4iwHYiepFLfABDWEpvzUBBu_F-kCL8Z18NHSpj2ywu/s400/mainboard_back.jPeG" width="392" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Delay board back side</td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td><td class="tr-caption" style="text-align: left;"><br /></td></tr>
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I couldn't tell if the relay was actually switching, as it was hard to hear it click over the sound of the footswitch. When I disconnected the foot switch board and triggered the switch with some wire I could hear the relay clicking, so the switching logic was probably good.<br />
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After hooking up a test signal and oscilloscope I could see that the input signal was reaching the first opamp stage but there was nothing at the output pin. I desoldered the LF353 and replaced it with a socket and a TL072 for now.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5V5y3mxhuBl5VjZ1tkg7YRc9EdhPpo_CnY1xkDpQEtggfj6vCsjbczLMr30opslOSIKM9wVbUvHWogJTZXSuBdqyfkT9P1LCeNzH3ehC_Vywk81uvQRDvDR7uXWBS7WuShGZVYW-sL1h0/s1600/removed_opamp.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1497" data-original-width="1600" height="373" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5V5y3mxhuBl5VjZ1tkg7YRc9EdhPpo_CnY1xkDpQEtggfj6vCsjbczLMr30opslOSIKM9wVbUvHWogJTZXSuBdqyfkT9P1LCeNzH3ehC_Vywk81uvQRDvDR7uXWBS7WuShGZVYW-sL1h0/s400/removed_opamp.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Removed LF353</td></tr>
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Now I had a clean signal in bypassed mode, but no delay. No switching waveforms on the BBD on the oscilloscope. No power at either the clock generator or BBD either. The schematic shows an NPN transistor/diode voltage regulator for these chips, I found that the 2N3904 transistor was blown to shit! After replacing with a new 2N3904 it regulator to around 7.4 volts. I'm not totally sure why this is needed as the BL3102 & V3205 should be happy to run on 9V, this may be a holdover from using older BBD chips. <i>(Update: it turns out that there are multiple V3205 datasheets online, with conflicting information. <a href="http://coolaudio.com/docs/COOLAUDIO_V3205SD_DATASHEET.pdf">According to Coolaudio</a>, the max Vdd for a V3205SD is 8V).</i><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0Od-oz1jOTaACaq0xh1m98S8sjqRlG-W5I-Qu0k-wJls_Fa4uPgOmiJDwW_t3nOGng-OSaVZ6hIC2hMBVyCGQpc8ujWNFGq-SlSKNAIXwbLMyZ4tLA7JD9JR_AoWcgOGospPwOf1ZEnil/s1600/IMG_1516.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0Od-oz1jOTaACaq0xh1m98S8sjqRlG-W5I-Qu0k-wJls_Fa4uPgOmiJDwW_t3nOGng-OSaVZ6hIC2hMBVyCGQpc8ujWNFGq-SlSKNAIXwbLMyZ4tLA7JD9JR_AoWcgOGospPwOf1ZEnil/s400/IMG_1516.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Epoxy case blown off voltage regulator pass transistor. I don't know how I missed this.</td></tr>
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I could now see clock signal at the BBD which varied with the delay knob as expected, but still no delay. I could see an input signal at pin 11 of the SA571 but nothing at the output on pin 10. I borrowed an SA570 from PDS delay pedal and this brought back the delay effect. Sounds great but not too different from other analog delays I have.<br />
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So: dead 2N3904 regulator, dead LF353 and dead SA571. I'm guessing this was fed too high a voltage from the wrong power supply. It's running happily 24 hours later with a new SA571 so this will probably go up for sale on Reverb pretty soon.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com1tag:blogger.com,1999:blog-942832708593410658.post-54268194692489039152018-12-07T21:26:00.001+00:002019-03-05T09:47:54.117+00:00Silvertone Bass 35<br />
This is a cool little solid state bass amp, I'm guessing dating to the 60s. No idea if Silvertone manufactured this, or if it was a rebrand, as there is very little information about this model online.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirojS63-ddm0lKtKuEi8dup1vAZflO_HIoItRABN1pPHR1fjGYZvxQqppDWwZd8IKbQ86AvhS5aD5CuMvKQyWAfSCRk04Qy1oJSMnv0IqPhiPl0LMuTEyc8tukH-VudMAOj8WmDEnNH0XJ/s1600/bass35.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="903" data-original-width="1600" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirojS63-ddm0lKtKuEi8dup1vAZflO_HIoItRABN1pPHR1fjGYZvxQqppDWwZd8IKbQ86AvhS5aD5CuMvKQyWAfSCRk04Qy1oJSMnv0IqPhiPl0LMuTEyc8tukH-VudMAOj8WmDEnNH0XJ/s400/bass35.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Solid State Bass 35</td></tr>
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No output signal. Only 5 transistors, so surely this would be easy? Instead of getting through this quickly I had it for several months, only looking at it when I had a few minutes to spare. If I had more space to work with this could have been much faster and easier. This has been a trend with physically large gear, I should really think about learning a lesson and getting a wide bench and keep it clean somehow.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW2GyDJAuPrdN0Nhyr2gzfdjypWFu322B74CFU0c8ER1yzElo6cMRkMlIOF5XWBXhpfloM1N8HLbXpMBXZwnl-QMubP25C99QhYDNJZ0vEZ2VrS0haa3u8UHx5rT1XQzXFEaJ9FAG-WO_-/s1600/IMG_1250.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW2GyDJAuPrdN0Nhyr2gzfdjypWFu322B74CFU0c8ER1yzElo6cMRkMlIOF5XWBXhpfloM1N8HLbXpMBXZwnl-QMubP25C99QhYDNJZ0vEZ2VrS0haa3u8UHx5rT1XQzXFEaJ9FAG-WO_-/s400/IMG_1250.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Single sided phenolic PCB</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-XA1vhX75djfmkFdvQwmOlbsbhsYIWFMqmg51WhBVeVk1Jy12HQlqHyDNuMjLclNV6H63Jkk0tvYAvpTOrDZYq8V2LVcUE386lKUFJPT-C70Bzgu5p6I0S0EOEhYSalrY4ePXJUraDs-6/s1600/IMG_1249.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-XA1vhX75djfmkFdvQwmOlbsbhsYIWFMqmg51WhBVeVk1Jy12HQlqHyDNuMjLclNV6H63Jkk0tvYAvpTOrDZYq8V2LVcUE386lKUFJPT-C70Bzgu5p6I0S0EOEhYSalrY4ePXJUraDs-6/s400/IMG_1249.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Full of cracks and mild corrosion</td></tr>
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This amp has been worked on in the past, and has some of the electrolytics replaced. It was also dropped on it's faceplate at some point in the past, and the phenolic PCB has cracked. The ground pour is broken in a few places and it has been bridged with solder.<br />
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<tr><td class="tr-caption" style="text-align: center;">Original output transistors.</td></tr>
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Most of the transistors appear to be branded with house-markings, as I can't find any references to their part numbers. I initially though output transistors were bad. They are marked "761" and "CG121", no info on these. One seemed to have a very low Vbe when measured with a DMM diode mode, which looked like a shorted junction. The TO-3 pinout is fairly standard for transistors, so I was assuming all cases were collectors. Collectors voltages were +35V and 0V, so I made guesses as to which output transistors were NPN and PNP types and then replaced with new 2N3055 and MJ2955 in TO-3 packages, new mica washers and new thermal grease.<br />
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<tr><td class="tr-caption" style="text-align: center;">Dead bass control/driver transistor</td></tr>
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After tracing the signal through the amp with a scope I found that nothing was getting to the output transistor bases. Nothing was passing the third transistor that drives the output transistors and implements the bass control. It was marked "5981 274 S6721", no idea. I desoldered this part and found that it was dead, completely shorted leads. I replaced this with a BD139. Based on a guess of the polarity of the original and the size of that package I thought this should handle the current requirements. With the BD139 I got some life, there was an output signal<i> sometimes</i>. Turning power on and off would sometimes get it working, sometimes it would stop. I found that there was a high-frequency oscillation at the output stage, if it drifted in and out of oscillation then things would work. Capacitors from collectors to base pins fixed this, values were just picked experimentally.<br />
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It still didn't sound right. There was an odd overtone riding on top of the signal that couldn't really be dialed out, though it sounded better at higher volumes. Another parasitic oscillation? Bias issue?<br />
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Around this time I bought a <a href="https://www.peakelec.co.uk/acatalog/dca55-atlas-dca-semiconductor-analyser.html">Peak Atlas DCA 55 Semiconductor tester</a><i>.</i> This is a very useful tool for testing transistors and diodes, and will also attempt to identify parts based on I/V characteristics. I still had the original TO3 power transistors<span style="font-family: inherit;"><span style="font-size: small;">, so I tried them out. One read a Vbe of 0.19V but was identified as PNP <i>germanium</i>, and working. I had assumed Vbe this low was a problem. After putting the old transistors back into the amp with new grease it sounded great, not very clean but not totally distorted either. The replacement silicon part wasn't biased correctly, the odd sound was probably some crossover distortion.</span></span><br />
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<span style="font-family: inherit;"><span style="font-size: small;">There is a diode from the base of CG121 which is probably used for biasing, I would guess that this is also germanium and modifying the amp to use new silicon transistors would involve replacing this as well.</span></span></div>
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<span style="font-family: inherit;"><span style="font-size: small;">The replacement BD139 runs quite warm, but not so much that I would worry about heatsinking it yet.</span></span><br />
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Here are measurements of the originals, they are surprisingly mismatched. This may not be a push-pull design at all.<br />
<br />7671 <br />NPN silicon<br />hfe 108 @ Ic 2.5 ma<br />Vbe 0.643V<br /><br />cg121<br />PNP germanium<br />hfe 59 @ Ic 2.5 mA<br />Vbe 0.190V<br />Ib 4.781 mA<br />
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<br /><br />Hopefully this is good for another 40 years.<br /><br />krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com0tag:blogger.com,1999:blog-942832708593410658.post-79610095393614402892018-11-22T17:46:00.001+00:002018-11-22T17:48:10.504+00:00Red Panda ParticleIt's been a while. I have been doing repair jobs and not posting them, so I will try to clear the backlog.<br />
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I bought a non-working Red Panda Particle granular delay for a decent price. This is fairly well documented as a Spin FV-1 design, but the granular delay programs and pitch-shifting & randomised modes really drew my interest.<br />
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The insides are fairly simple - the FV-1, a 24LC32a serial EEPROM, a 74HC148 priority encoder (to decode the rotary switch and select which program to run) and a quad OPA4134 opamp. The "chop", "delay/pitch" and "param" pots are read by the FV-1, the blend and feedback controls appear to be done in the analog domain. This looks more or less like a reference FV-1 design, all the magic is in the program code.</div>
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The PCB layout is nice, pots and jacks are board-mounted and the DC jack is on a connector so the entire board can be removed or tested before installing in an enclosure. They use a PCB mounted spring to ground the enclosure, like the modern EHX designs, but this one seems to be contacting an oversprayed section.</div>
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<tr><td class="tr-caption" style="text-align: center;">Interior layout.</td></tr>
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This pedal passed no signal in effected mode. I probed the OPA4134 and the first opamp that drives the mix control was stuck at near ~8V DC. After replacing the chip everything worked.<br />
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<tr><td class="tr-caption" style="text-align: center;">IC10 removed.</td></tr>
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This is a really cool design, in that it's very different to nearly every delay I've used before. It is quite difficult to predict how the different modes will sound, and I think this would need some significant playtime to learn. Unfortunately this one came along at a time when I didn't have a lot of free time or desire to keep amassing pedals, so I have sold it on.<br />
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I did dump the EEPROM. Looking at it briefly with the excellent online <a href="http://s.shift-line.com/decompiler2/">FV-1 decompiler</a>, each program looks to have disassembled correctly and makes some sense. I'm reluctant to share this, as this is really the only unique part of the pedal, and AFAIK it hasn't been cloned. If you have a genuine repair need (pedal with dead ROM) then get in touch, maybe I'll help. I may also revisit this and get it running on a different FV-1 board at some point in the future.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com7tag:blogger.com,1999:blog-942832708593410658.post-13579202874600987272018-03-01T11:31:00.002+00:002018-03-01T11:31:54.216+00:00Voodoo Labs Amp Selector This is a 2 input, 4 output amp selector and A/B switch. One guitar can drive 4 isolated outputs, all with their own volume controls and ground lifts. There is some preset save/recall functionality, so I am expecting a microcontroller in here somewhere. This is exactly the sort of thing I would have loved to play with when I was renting a practice room and had access to lots of amps, but it will probably just be sold on nowadays.<br />
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<tr><td class="tr-caption" style="text-align: center;">Main PCB</td></tr>
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No surprises on the insides - there is an <a href="https://www.nxp.com/docs/en/data-sheet/P87LPC764.pdf">P87LPC764</a> MCU reading switches and turning JFET switches on and off. A MAX1044 provides a -9V supply. The transformers are 6 pin devices with any labels or markings removed. There is one OPA2134 dual opamp, and a 24C01 serial EEPROM for presets.</div>
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<tr><td class="tr-caption" style="text-align: center;">Hacked in parts at the power input.</td></tr>
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The back of the PCB has some factory bodges/mods at the power input - there is a series resistor and a capacitor added to the MAX1044 input.</div>
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The digital side seemed to work, everything lit up and it did switch signals, but there was lots of bleed between outputs and the volume was quite weak.<br />
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I know from experience that a MAX1044 will only tolerate ~10V input before dying, so I looked there first. The inverted voltage was measuring less than -1V. I desoldered the MAX1044 and replaced it - no change. There is a zener diode at the input pin which should limit the input voltage, I lifted this part out and now I had -8V and a working pedal.<br />
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<tr><td class="tr-caption" style="text-align: center;">Replaced MAX1044 (pictured here sitting crooked in a socket) and lifted diode D10</td></tr>
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This diode was a 1n5239b (9.1V 0.5W zener) so I replaced it with a 1W part I had at hand. Now the negative voltage was pulled low again! It turned out that the cap across the zener that was added to the packside was leaking. It still measured 2.2uF but had ESR >5 ohm - this looks like a dipped tantulum part. I replaced with a similar electrolytic. It's not even technically needed, the cap is just stabilising the 9.1V zener clamp when it's conducting.</div>
krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com12tag:blogger.com,1999:blog-942832708593410658.post-12377786332535352552018-03-01T10:41:00.000+00:002018-03-08T13:40:44.078+00:00TC Electronics Nova Drive NDR-1Programmable overdrive & distortion from TC Electronics. All overdrive/distortion parameters are controlled digitally, so presets can be saved and recalled, the order of the two circuits can be changed, they can be run in series or in parallel. All of this can be triggered by MIDI.<br />
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TC did a Nova series of pedals and multi-effects units, but I don't think they were all built around a common digital design (like the Line 6 4x4 series). TC stuff is interesting as they have a history of high quality and targeting high-end markets and they tend to use fairly modern designs and parts. Unfortunately they don't seem to release much information or contract out any repair services, so I have not come across any modern TC Electronics schematics, either official or leaked. <br />
TC were sold to Behringer in 2015 and their latest range of pedals look to be more standard stuff, a bit watered-down compared to the Nova series. I'll reserve judgement until I see one.<br />
This series used a 12V power supply for some reason (why not 9V, like everything else?)<br />
This Nova Drive started up but only passed a signal in bypass mode. The LED display and indicators did react to the knobs and to button presses, which at least meant that the digital section is working and the problem was likely in the analog end.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0hEgh7z5mH7KcYXMjqohaOXsoHc5x64uS4K8necEinSwRKkh1ufM2wGB8BQlHS0F_B2un4ZCIaepuqPPNeXDVmt6TUEFKEkYGsJQ8WOiINUKDlbmuD1pUktLBqjatolD0pcIjFCt0nAN9/s1600/top_pcb.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1393" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0hEgh7z5mH7KcYXMjqohaOXsoHc5x64uS4K8necEinSwRKkh1ufM2wGB8BQlHS0F_B2un4ZCIaepuqPPNeXDVmt6TUEFKEkYGsJQ8WOiINUKDlbmuD1pUktLBqjatolD0pcIjFCt0nAN9/s320/top_pcb.JPG" width="278" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Top PCB (digital)</td></tr>
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The build quality is really nice, they use a folded and tapped sheet metal chassis instead of cast box. There are two PCBs inside, the first is a "mezzanine" board with the encoders, buttons and displays. There is an Atmel ATmega168 and some '595 and '165 shift registers for digital IO. I'm pretty sure the ATmega is reading out pots and buttons and controlling something on another PCB to vary the effect parameters, as well as driving the LED displays and responding to MIDI commands. I would guess that this top PCB is probably very similar across all the Nova pedals. I am assuming the ATmega has some code-protection so I haven't tried desoldering and dumping it.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSAVzuUAYvvhPI5WNHWw6GizdT_ruLioTIuMMu3k7wJUBtfP9tRixwIsL3XA6GzDwrTJeRcPmXeaT57E3JuUUE5FlfdhmjPz2QFvpHPvQjBSadyc-LyiNR0bMVe6A6CQtFQ7Oi_1mzicK0/s1600/bottom_pcb.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1308" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSAVzuUAYvvhPI5WNHWw6GizdT_ruLioTIuMMu3k7wJUBtfP9tRixwIsL3XA6GzDwrTJeRcPmXeaT57E3JuUUE5FlfdhmjPz2QFvpHPvQjBSadyc-LyiNR0bMVe6A6CQtFQ7Oi_1mzicK0/s320/bottom_pcb.JPG" width="261" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Lower PCB (analog)</td></tr>
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The bottom PCB fills the whole enclosure - it has a bunch of opamps (presumably the analog overdrive and distortion circuits), DG441D quad analog switch ICs, switching power supplies, the MIDI optoisolator, a relay and a <a href="https://www.blogger.com/%C2%A0https://www.cirrus.com/products/cs3308-18/">Cirrus CS3308</a>. The CS3308 is a cool part, it's an 8-channel digitally programmable volume control. Presumably each channel is mapped to one encoder (4 knobs for overdrive and 4 for distortion) and the ATmega sets the levels over SPI or I2C. TC have used the +-5V version with 123 dB of dynamic range, which is kind of ludicrous for a distortion pedal.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOs9NKtCINF1yKCoM4Tm1BZu0HsaPdW4gurOkoB8Eq7cqIqp8PMhrY8CRfjGC0K2ny6-43wkXTiHIdyPfH4CILCsdrHs2hZpo7AdMdNYl-FOUxE0gSjidvX5FEwLGxDNUsP1ybnUZ06MKJ/s1600/backside.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1528" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOs9NKtCINF1yKCoM4Tm1BZu0HsaPdW4gurOkoB8Eq7cqIqp8PMhrY8CRfjGC0K2ny6-43wkXTiHIdyPfH4CILCsdrHs2hZpo7AdMdNYl-FOUxE0gSjidvX5FEwLGxDNUsP1ybnUZ06MKJ/s400/backside.JPG" width="381" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Lower PCB, backside</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih7w_fteVvy1LaqahTvAX6iHsRHb7Eajb2KE0G5WnI-aAaibs4Yu8MpGN5fifLy7t8_xZ7mEKeohzf1lWxWXVOKrPWVJmB7YXpmds_EXQWM4V9T4DIBxouBdeDhQycVThZVZV1IHWOmf37/s1600/ic3.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1410" data-original-width="1600" height="351" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih7w_fteVvy1LaqahTvAX6iHsRHb7Eajb2KE0G5WnI-aAaibs4Yu8MpGN5fifLy7t8_xZ7mEKeohzf1lWxWXVOKrPWVJmB7YXpmds_EXQWM4V9T4DIBxouBdeDhQycVThZVZV1IHWOmf37/s400/ic3.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">U3 generates -12V from 12V input</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjheUzZG6hgpzc3jxYEi4cq145cP15iTiyC9w6g2H46Q5Z7-dXN8W7lZk-znq90qS5QrMPYc9X0I_eNXCL4UcC13p2guaGWZzOu3cR_0byfDd-gaBxDeEt3GuJCZFzOkvNiaeqvGvbs08yG/s1600/IMG_1305.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjheUzZG6hgpzc3jxYEi4cq145cP15iTiyC9w6g2H46Q5Z7-dXN8W7lZk-znq90qS5QrMPYc9X0I_eNXCL4UcC13p2guaGWZzOu3cR_0byfDd-gaBxDeEt3GuJCZFzOkvNiaeqvGvbs08yG/s400/IMG_1305.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All parts on this side are glued in placed before soldering</td></tr>
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The bottom PCB is very parts-dense, but helpfully there are test points for all supply voltages. I found that -12V was reading very low and so all of the negative supplies that are derived from -12V were also missing. -12V appeared to come from a switching supply controlled by a <a href="http://www.onsemi.com/PowerSolutions/product.do?id=CS51411">CS51411</a> on the underside of the PCB, the circuit looks liked a close match to the inverting converter in the datasheet (Fig 25). The inductor was getting burning hot, so the switching IC was a pretty likely culprit. TC used a double sided load for this PCB, and parts on the underside are wave-soldered instead of reflowed, which means they are all held in place with a dot of red epoxy. Desoldering the IC took a lot more heat and force than I'm used to but it did eventually lift off. It still didn't work with a new chip, solid 12V DC across the inductor with no switching happening, which explains the heating. The SYNC pin did have a ~340 kHz square wave - I don't know if this was also present on the original chip. The huge number of test points on the back of this larger PCB suggests TC use some kind of bed-of-nails jig for testing during manufacturing.<br />
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Around this time I held my hand over the board when powered up and found another hot spot. One of the two DG441D switch ICs was also running hot, so I desoldered it. This part does run off +12V and -12V rails, so it may have killed the -12V supply when it failed.<br />
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There is another switching power supply using a L5970D controller - this one is generating 3.3V for the digital parts and was working correctly.<br />
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As I knew there may have been a short from -12V to ground or some other supply, I wanted to see if I could completely isolate the CS51411 from the -12V supply and use an external power supply to provide -12V. I removed the output capacitor and the inductor. Using an bench supply wired to the board and providing -12V, the pedal worked. Surprisingly, it pulled over 100 mA which seemed very high for some opamps and switch ICs so there may have been some other damaged part on that -12V rail.<br />
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The series/parallel switching did not work, only series mode passed a wet signal. This confirms the DG441Ds are routing the signals into series or parallel combinations, one of them was still missing. A new IC here restored all modes.<br />
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The CS51411's inductor measured 33uH out of circuit which seemed correct. I decided to try swapping it with <a href="http://ie.farnell.com/bourns/sdr0604-330kl/inductor-smd-33uh-1-1a/dp/1828007">this part</a>, which fixed all the power supply issues. I am guessing that the old inductor got so hot that it reached it's curie temperature and it's magnetic properties changed (??) The new part runs cool. Looking again at the CS3308 datasheet shows it pulls 36 - 50 mA on both positive and negative analog supplies (!), which explains the high power consumption seen earlier, and why the pedal originally shipped with a 12V supply rated for 400 mA. This chip does run noticeably warm, but the power consumption matches the datasheet figures. I can only guess that power consumption is targeted high to help lower noise and increase dynamic range. For a distortion pedal a low-power version with poorer specs would probably be a much better fit. The pedal will actually work with 9V input, and will generate a -9V supply instead, but will need a beefier supply than is usually seen on pedalboards.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmlq9dhXddprnqFIERJyZcPMIDLuq_ITgA7kNVBm6WyMak1zFwfSIJ45ySY4iWcFf042yhb93agtTEFLfnveBrj4UDoslVzTWgTtUDiG1hOxrv9wwIzZBXeT286TIz9z3yZG1CbgTLCBL0/s1600/IMG_1321.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmlq9dhXddprnqFIERJyZcPMIDLuq_ITgA7kNVBm6WyMak1zFwfSIJ45ySY4iWcFf042yhb93agtTEFLfnveBrj4UDoslVzTWgTtUDiG1hOxrv9wwIzZBXeT286TIz9z3yZG1CbgTLCBL0/s320/IMG_1321.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All good again.</td></tr>
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I broke the ribbon cable connecting the two boards when I was working on this. I just replaced it with individual wires - I would really like a tool that strips ribbon cable so I could just buy a small reel, if anyone knows of one please let me know.<br />
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krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com10tag:blogger.com,1999:blog-942832708593410658.post-31474518732357532282018-02-18T17:43:00.000+00:002018-02-18T17:43:05.938+00:00Electro-Harmonix PitchforkI don't know if the PitchFork exists alongside the <a href="https://falseelectronics.blogspot.ie/search/label/pog">POG series</a> for market segmentation reasons or as a direct competitor to the Whammy pedal. Whatever the reason, EHX have another polyphonic pitch-shifter/harmonizer with a slightly different feature set, and strangely, a lower price. This one will add a harmonized voice at a selectable interval, at a higher or lower pitch or both. You also get a clean blend. There is an expression pedal control and the footswitch can be set to work in a momentary mode, which suggests Whammy style punch-ins, but it does POG style octaves as well.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjICxFUmvEhkP8X-N-7e56Evb5BrwzvoLvES1t8_3H2whtMG2vcCGNrkeeH-BaqCmJgzNeI_KVnh_v_lanWyLrSrDepQ_w0KKCsHamiUIsC9GUPuJ76VN-atj-IRAp6fts8OEORWUKQgr3_/s1600/top.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="975" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjICxFUmvEhkP8X-N-7e56Evb5BrwzvoLvES1t8_3H2whtMG2vcCGNrkeeH-BaqCmJgzNeI_KVnh_v_lanWyLrSrDepQ_w0KKCsHamiUIsC9GUPuJ76VN-atj-IRAp6fts8OEORWUKQgr3_/s400/top.JPG" width="243" /></a></div>
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The insides are very similar to the newer POG pedals, with an Analog Device Blackfin DSP (<a href="http://www.analog.com/en/products/processors-dsp/blackfin/adsp-bf592.html">ADSP-BF592</a>) and a AKM <a href="https://www.akm.com/akm/en/product/datasheet1/?partno=AK4552VT">AK4552</a> 24-bit/92 kHz ADC/DAC. There is also a 25L1005 serial flash with the program code - I did end up desoldering and dumping this in case I come across another and need it.<br />
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<tr><td class="tr-caption" style="text-align: center;">Picture taken after repair - clean.</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8YaYmDt4yZhBcMfjCWlfpiwE7zIF2h58S-RGaDcUBZPiTuCswCbF2KZfiaTB6efJOYGTPbsqd-qeHVuyJ2QttJuKLJ4kDv7FKmiL-AwR7mj8iZj0jTWd-ZW29CGU3-wb1FBZMRIOEV4g2/s1600/back.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1329" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8YaYmDt4yZhBcMfjCWlfpiwE7zIF2h58S-RGaDcUBZPiTuCswCbF2KZfiaTB6efJOYGTPbsqd-qeHVuyJ2QttJuKLJ4kDv7FKmiL-AwR7mj8iZj0jTWd-ZW29CGU3-wb1FBZMRIOEV4g2/s400/back.jpg" width="331" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Taken before repair - PCB appears cloudy</td></tr>
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This one would not show any signs of life, and turned out to be shorting out my power supply. The reverse polarity diode (D2) on the back of the DC jack measured as a short circuit, so I removed it and the pedal worked! For about 10 or 15 minutes. Something else between 9V and ground was shorting.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyJk5M0NWfsgGqz1gP_P8VaIzJ3qqZv9e4mmSbaOvqrY36ZvwuKNwdMkYV3OJxygiQJmkMXYPVRhyphenhyphenMCjt58oE0B2gpXU8Ba6IlR18L2WPZ74V99QIrm9T9rIALp6lxhxM4AqabSxEyJdhd/s1600/IMG_1300.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyJk5M0NWfsgGqz1gP_P8VaIzJ3qqZv9e4mmSbaOvqrY36ZvwuKNwdMkYV3OJxygiQJmkMXYPVRhyphenhyphenMCjt58oE0B2gpXU8Ba6IlR18L2WPZ74V99QIrm9T9rIALp6lxhxM4AqabSxEyJdhd/s320/IMG_1300.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">11-detent "Mode" pot showing some stains</td></tr>
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After a little while spent probing around and occasionally getting a short burst of life followed by nothing, I noticed that one pot had some corrosion on the back sides. I desoldered it and wire-brushed it until it was clean but couldn't figure out how this would be the cause of the problem. The corrosion was probably from some liquid spilled into the pedal.<br />
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I could see some kind of dirt at the power jack, so I removed it and things were then pretty obvious, some liquid had been trapped between the jack and PCB and had corroded the board, causing intermittent shorts.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXBVBMVbFGQGRGXaSICY3QvIWmXdJIkdCkEAVhKuc3ey0_HUkGFtegPMxoGwfZHNLzlwQpgYxhyL75FliPUXUbog10zQ4A3rgSj5xo7luv1eLEGIznmdI04-OZl_VGWlHsnR6crZrZFeHi/s1600/IMG_1301.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXBVBMVbFGQGRGXaSICY3QvIWmXdJIkdCkEAVhKuc3ey0_HUkGFtegPMxoGwfZHNLzlwQpgYxhyL75FliPUXUbog10zQ4A3rgSj5xo7luv1eLEGIznmdI04-OZl_VGWlHsnR6crZrZFeHi/s400/IMG_1301.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Original DC jack</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpNbG0n0H7H_RN0k_TI5zg35oRrR5AY7OCI869T0_OyyQ5GRHhZPScIUCNcx3E0HEBKwYTkIJL40zzb_T9qDptSmUuL0rV7Ic0p1nbn3sY5iQpjlVPIqxM7ShvD4GgN8NZrQ6ngXKnPQmi/s1600/IMG_1302.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpNbG0n0H7H_RN0k_TI5zg35oRrR5AY7OCI869T0_OyyQ5GRHhZPScIUCNcx3E0HEBKwYTkIJL40zzb_T9qDptSmUuL0rV7Ic0p1nbn3sY5iQpjlVPIqxM7ShvD4GgN8NZrQ6ngXKnPQmi/s400/IMG_1302.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">..and underneath the jack</td></tr>
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Some scrubbing with PCB cleaner and a new DC jack later and it is rock-solid. The rest of the board was cleaned as well, what looked like cloudy flux residue was probably stains from dried liquid.<br />
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This is a pretty clear case, something was spilled and the pedal was never taken apart and cleaned afterwards. If it had been looked after at the time then no parts would have needed replacement. Underneath DC jacks and instrument jacks are probably the worse places for this, as they can trap liquid easily.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com8tag:blogger.com,1999:blog-942832708593410658.post-74899767625406027152018-02-01T11:29:00.000+00:002018-02-01T11:29:34.225+00:00EBS ValveDrive<div class="separator" style="clear: both; text-align: left;">
This is another 2017 leftover, I want to write it down before I forget it.</div>
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EBS's ValveDrive is a valve overdrive/preamp that uses a single 12AX7 dual triode. This is the original version, there is a newer model that adds a balanced XLR output and has an internal switching power supply.</div>
The "vintage" circuit is similar to various Fender Baseman preamps, the "modern" setting adds some diode clipping - the original schematic is available at <a href="http://freestompboxes.org/viewtopic.php?f=1&t=8368&start=20">Freestompboxes.org</a>. It uses a 12 VAC power supply and has an internal 12 VAC transformer wired "backwards" to supply the high voltage for 12AX7 plate. This used to be a very popular pedal with bass players, especially as the high voltage supply means it can get really loud and will happily drive a standalone power amp. Maybe it is not as fashionable right now, I don't see them as often as ~5 years ago.<br />
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Like nearly everything that comes across my bench, it doesn't work.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBmsBYxCCyFvAXuoHNw9-X1QwLtYLAkyObVP2N3VZhQEK-2avSo78sANEY8m8-5BFilV-udXlh96qKYwm1oO5UQf-95mrKRBOK52C19vqIPxQuo2jGe9QIIUG3a57VX7nhGb6qRXUuHGex/s1600/top.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1454" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBmsBYxCCyFvAXuoHNw9-X1QwLtYLAkyObVP2N3VZhQEK-2avSo78sANEY8m8-5BFilV-udXlh96qKYwm1oO5UQf-95mrKRBOK52C19vqIPxQuo2jGe9QIIUG3a57VX7nhGb6qRXUuHGex/s320/top.jpg" width="290" /></a></div>
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After verifying that my 12 VAC supply was working, I removed the top shield and looked at the valve. No wonder it does nothing, the vacuum has escaped from this one.</div>
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I put in a Jet City <a href="http://www.jetcityamplificationstore.co.uk/product/retrovalves/">RetroValve</a> that I keep around for testing, and still nothing. After pulling the valve and probing the socket I measured 0V at the plates - something wrong with the high voltage supply. The heaters are getting 12VDC, so low voltage power should be OK.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMzvATcX2rdB-868qt2V7Ugsj1DOY-loZNzmWg-I97bu7SiTt8E1SLXnKYsQd-rnI6oTe1iTwLPx-0H7_gJ3aUIrLFptDC9nkZUe20FavErsc32h3aslAdPLKbauvIyUPBn_EZ_YFTto76/s1600/tube.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1097" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMzvATcX2rdB-868qt2V7Ugsj1DOY-loZNzmWg-I97bu7SiTt8E1SLXnKYsQd-rnI6oTe1iTwLPx-0H7_gJ3aUIrLFptDC9nkZUe20FavErsc32h3aslAdPLKbauvIyUPBn_EZ_YFTto76/s320/tube.jpg" width="219" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A leak has developed somewhere...</td></tr>
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The build quality is very good, a nice folded steel enclosure and multiple PCBs connected together with ribbon cable (switching signals) and runs of coax for the audio signals. This was probably expensive to manufacture but it's hard to kill and convenient to work on.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZgsM5h4Rmr87SmohVGyIqT2TxMq6YMyXncAkRwAcIGyaXSHyyzU48haoA0Sgv_r2ES1hPRkHZWqWYGEpZpjCag6ZnC4PR1HtDZ4snKjWKS2OHBInpx2fdezHT6r_28H6RLgOvOhwS2rKA/s1600/pcbback.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1397" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZgsM5h4Rmr87SmohVGyIqT2TxMq6YMyXncAkRwAcIGyaXSHyyzU48haoA0Sgv_r2ES1hPRkHZWqWYGEpZpjCag6ZnC4PR1HtDZ4snKjWKS2OHBInpx2fdezHT6r_28H6RLgOvOhwS2rKA/s320/pcbback.jpg" width="279" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4R9wGieBmVBBBLKUkW1Vc062xUnZwz89GTHghi_KJaG5hLb7DbOewdZ8t28frOMUsld-6pTaEZC_gJhbOYHGtRjwzcaDm_b8uqJqueDp64XoLZdKaY7iV1S0dRGpOjojuNNUETY1l9g7n/s1600/pcbtop.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1288" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4R9wGieBmVBBBLKUkW1Vc062xUnZwz89GTHghi_KJaG5hLb7DbOewdZ8t28frOMUsld-6pTaEZC_gJhbOYHGtRjwzcaDm_b8uqJqueDp64XoLZdKaY7iV1S0dRGpOjojuNNUETY1l9g7n/s320/pcbtop.jpg" width="257" /></a></div>
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The high voltage transformer is on the lower left of the topside of the PCB. The surface mount fuse on the backside is not blown, but the transformer looks weird, as if it had been re-soldered or replaced. The output winding only measured around 0.5 VAC with the power supply connected.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCPYss6p9WW5Zv8W1zm53awq6kD-sCczIUjHVNV4ocKa4nuwPBVX6xnJxa0GzjIT8hHKGPV0pADAfvt0Sn3SuwEsUxXzSVDfSDmTQlAz7vkhyphenhyphen5u06iEKSZDe46wbJmpy898B5KGvr7idPz/s1600/IMG_1007.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCPYss6p9WW5Zv8W1zm53awq6kD-sCczIUjHVNV4ocKa4nuwPBVX6xnJxa0GzjIT8hHKGPV0pADAfvt0Sn3SuwEsUxXzSVDfSDmTQlAz7vkhyphenhyphen5u06iEKSZDe46wbJmpy898B5KGvr7idPz/s320/IMG_1007.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Transformer pins are not coming through the plated holes...</td></tr>
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<b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjK3ft-eJFUuoaPqkzwcD2_ZNZEDTFLyhiySJnS2Afb6tzJhBYEFC6o1WbgRsAYiIk7_WFVWVnFcVcwQBl-AZ6DnnrmKR-l58nTvwiu85rRt3pjJ4sYT8Lu50iPZrvm2QJQCxQj0PXDhrcZ/s1600/IMG_1009.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjK3ft-eJFUuoaPqkzwcD2_ZNZEDTFLyhiySJnS2Afb6tzJhBYEFC6o1WbgRsAYiIk7_WFVWVnFcVcwQBl-AZ6DnnrmKR-l58nTvwiu85rRt3pjJ4sYT8Lu50iPZrvm2QJQCxQj0PXDhrcZ/s320/IMG_1009.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Additional holes drilled in PCB...</td></tr>
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Once it was desoldered, it was obvious why things looked strange. The transformer pins were not going through the plated through-holes, instead someone had drilled holes in the PCB (!) and bridged over to the pads with some bus-bar to make the transformer fit. The low voltage measured at the transformer made sense now, scaling 12 VAC to 230 VAC is a roughly 19.16 ratio. If the transformer was scaling 12VAC <i>down</i> by the same ratio I should get 0.6 V AC, which is pretty much what I had measured.<br /><br />I reinstalled the transformer the other way round and now measured 230V AC, and 400+V DC at the valve plate with no valve installed. With a new valve installed, this dropped to around 350V, and everything worked and sounded great. The original filter capacitors were only rated to 400V, so I replaced this with 450V rated Nichicons in case this was ever left running with a dead or missing valve.</div>
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The part number on this transformer is slightly different from the schematic's part list, and obviously the footprint is different as well. My guess is that someone attempted to replace the transformer, installed it backwards, and then gave up and sold the pedal on. The slightly higher plate voltage(~350V vs 300V) is probably due to small differences between transformers.</div>
krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com4tag:blogger.com,1999:blog-942832708593410658.post-84123480237380169842018-01-31T18:49:00.002+00:002018-01-31T18:49:35.948+00:00Tech 21 XXLI picked up this 90s Tech 21 XXL as I had read that it was a "sleeper", a nice distortion but not particularly well known. I knew that the design was based on opamp clipping with no diode clipping. I have never built or (to my knowledge) even played anything like that, so I was curious and also pretty confident that this would be simple to repair. This one would power up and would pass a bypass signal but the effected signal was very quiet - volume and gain had to be cranked all the way to hear anything. The tone knob sounded like it was working correctly. A bad opamp or switching FET maybe.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkyxK2Rr45Cjevvh-m4coBzi0Lwg0F0jSf5apJzXf6IUODr3UUXsE-G87pKafQ976-HmfgAoyj9OjsLp8DbhJBFcTHLj1tvqS6r7iexHZ1Pjpgx2AKwxRHUs-jbaWrIScFCbkM1vspmbal/s1600/top.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1286" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkyxK2Rr45Cjevvh-m4coBzi0Lwg0F0jSf5apJzXf6IUODr3UUXsE-G87pKafQ976-HmfgAoyj9OjsLp8DbhJBFcTHLj1tvqS6r7iexHZ1Pjpgx2AKwxRHUs-jbaWrIScFCbkM1vspmbal/s400/top.jpg" width="321" /></a></div>
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The insides were a bit of a surprise. All the jacks and pots are board-mounted, but it looks like it was assembled using the least amount of solder possible. A lot of the through holes are not completely filled. Re-soldering all these joints didn't help.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghzeuJ2nmLy7QbfHfiHKp_dFa1m0H82Dbi3juTWBjU1gzk1FBwVZ7v94w2VoTmPjMXtJYtcoG_5cacwCFob2ND1d7B98eH8bJBPF2-EhEhJKAODoHeVWmhsN9t_fXXn-oR2BN0TnvoBMu2/s1600/IMG_1291.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghzeuJ2nmLy7QbfHfiHKp_dFa1m0H82Dbi3juTWBjU1gzk1FBwVZ7v94w2VoTmPjMXtJYtcoG_5cacwCFob2ND1d7B98eH8bJBPF2-EhEhJKAODoHeVWmhsN9t_fXXn-oR2BN0TnvoBMu2/s400/IMG_1291.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Dull joints, very little solder</td></tr>
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This construction style is very annoying to work with. The input/output jacks do not butt up flush against the sides of the enclosure like with many other common designs, instead they extend through the sides. This means that the whole pedal has to be basically assembled inside the enclosure, the jacks and pots are installed and the PCB is aligned with all of their pins and then soldered in place. This seems very labour-intensive and makes any kind of repair a real pain.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_yESZzsRhMdulrIZfbvOGnrlVTXHpvYfycYq5jXMiE8QWHMSdO-0RQeLgg0bYbGM3vaD0hPQN30TdTiGWT4G8Igc6PEOc3cWvzxwK0YnTUAh5RvYw9EmLSkdA9m9wDbQhStH9hIQxdFeH/s1600/pcb.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1340" data-original-width="1600" height="333" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_yESZzsRhMdulrIZfbvOGnrlVTXHpvYfycYq5jXMiE8QWHMSdO-0RQeLgg0bYbGM3vaD0hPQN30TdTiGWT4G8Igc6PEOc3cWvzxwK0YnTUAh5RvYw9EmLSkdA9m9wDbQhStH9hIQxdFeH/s400/pcb.jpeg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">WTF</td></tr>
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After desoldering the 1/4" jacks and DC power connector I managed to get the PCB out and found another surprise on the other side. Tech 21 have used a SMD design (fine) but have covered it with a block of <a href="https://en.wikipedia.org/wiki/Potting_(electronics)">potting compound</a>, presumably to prevent clones of the distortion circuit. Unfortunately this makes repair much more difficult as well.<br />
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The switching FETs actually seemed to be working correctly, so I decided to see if I could remove the potting (there are methods for this written up online, often described as "de-gooping"). I guessed that potting material for surface mount parts are probably softer than old-fashioned epoxies to prevent them from cracking solder joints as the compound cures. I hoped that heating with hot air and picking with a tweezers might be hood enough.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAfr2oExsqWyd43miSeATbtdrG0qGANx87Y_GhFXIo_DxPvV_UCtLw-98PqrlKHZsidK9BsdR0aE_ZTLj1VORs0a3xEsAll2MkM6cO8DIIcaNG3YbyWzpieWJe6O7dR-CDA32zLZTnk8zH/s1600/IMG_1293.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAfr2oExsqWyd43miSeATbtdrG0qGANx87Y_GhFXIo_DxPvV_UCtLw-98PqrlKHZsidK9BsdR0aE_ZTLj1VORs0a3xEsAll2MkM6cO8DIIcaNG3YbyWzpieWJe6O7dR-CDA32zLZTnk8zH/s400/IMG_1293.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Potting removed, plus some parts</td></tr>
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De-gooping went fairly well, I started at 100C and the compound cracked and separated from the board in large pieces. I increased the temperature as I went but eventually went too far (I think above 250C) and re-flowed some solder joints - this meant an entire chunk pulled away from the board, holding two opamps and some passives with it. The resistors and caps were easy enough to separate and re-populate, the opamps were replaced with new parts based on a <a href="http://www.diystompboxes.com/smfforum/index.php?topic=29094.0">schematic I found</a>.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyao2OONa8URmXmCg1U0yAyXkSKKk32V-ss7G9IL6B7hcQ1Nzgi5AljYg_aCjs_gSfxO4168Xx9v3G0Cs5gY96G9jHJjluGsIEiyngI2qksR-SScCOF_GYVk-LUAna9go0HLduunANx135/s1600/IMG_1331.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyao2OONa8URmXmCg1U0yAyXkSKKk32V-ss7G9IL6B7hcQ1Nzgi5AljYg_aCjs_gSfxO4168Xx9v3G0Cs5gY96G9jHJjluGsIEiyngI2qksR-SScCOF_GYVk-LUAna9go0HLduunANx135/s320/IMG_1331.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Restored jumper. Cut trace is visible.</td></tr>
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Another surprise, my pedal is a different revision from the one photographed on Diystompboxes. It has a cut trace and a jumper wire embedded inside the epoxy block. Is this a genuine correction, or something designed to make reverse-engineering more difficult?<br />
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The pedal still didn't work with new opamps, but now that I could probe them I could see one was not getting any bias voltage on one of the inputs. The Warp control which sets the DC bias of the first opamp was not connected to +9V, I found a trace to the pot that was open circuit, possible from a scratch from a nearby electrolytic cap. A jumper wire fixed this.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhhynzRMGX1hj5umSsVamM6L00VAdzNGObpvbSNFXOiE7oexWsuP6aj5hAw5yVQ23jaNgZtLZqPuKwaHOJjekDPtG1x137sz1yeNAO3qoLJxZUm6EEXxqTn8V1tQ0QCkny7xiUiLNoOeGFR/s1600/IMG_1330.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhhynzRMGX1hj5umSsVamM6L00VAdzNGObpvbSNFXOiE7oexWsuP6aj5hAw5yVQ23jaNgZtLZqPuKwaHOJjekDPtG1x137sz1yeNAO3qoLJxZUm6EEXxqTn8V1tQ0QCkny7xiUiLNoOeGFR/s400/IMG_1330.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Restoring +9V to Warp pot.</td></tr>
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Re-assembling was another pain in the ass, I broke the DC jack and had to order a <a href="http://ie.farnell.com/cliff-electronic-components/fc681465p/dc-skt-dual-2-1-2-5mm-pcb-dc10lp/dp/1854512?CMP=i-ddd7-00001003">replacement with PCB pins</a> instead of solder lugs. Getting the board into the enclosure and aligned with the jacks so they can be soldered is fiddly, in retrospect I should have tried to replace the jacks with the more common units that have a parts that threads from the outside of the enclosure, like modern EHX stuff.<br />
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The XXL sounds quite good - less compressed (and less sustain) than what I would usually expect from a diode-clipping distortion like a RAT. The Warp control doesn't seem to do much throughout a lot of it's range. It also does very little with a weak input signal (especially single coil pickups), probably because the first opamp stage isn't driven into clipping. With a loud signal generator I could different hear distortion flavours, presumably the clipping gets more or less symmetrical through the pot travel. Online reviews and clips confirm this, so I'm confident this is working as expected.<br />
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I like this pedal, but I'm a bit soured by the weird construction and the complete lack of giving-a-shit towards repairs. Uncovering the circuit took less than an hour, so it's not much of a deterrent to anyone who wants to make a clone, but it's definitely a hurdle for finding what has wrong. I'm not sure if I think it's worth looking at more Tech 21 stuff.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com1tag:blogger.com,1999:blog-942832708593410658.post-50251172675468210982017-11-19T17:14:00.001+00:002017-11-23T19:52:31.457+00:00Eurotec Black Box Faze ModuleEurotec was a brand run by Sola/Colorsound in the late 70s. They released a line of pedals called the "Black Box" series which seemed to be re-issues of their earlier products as well as some clones of contemporary designs. The pedals could be used individually with battery power, or plugged into a "Black Box Module Energiser" base station that could power and route signals to four modules. I don't know if this modular system was successful but it's interesting to see an earlier commercial stab at a pedalboard concept.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXkQ2O5ipKCBQWqaJOwBNYSXvO9t6dWkv-y4sh9ywYfHvVnodxec6N6klXFMHaWgv2Z51JSMge2OjegHv5WrRxXRU160kXuT1hs2fvBol203zIp6ds4zIoijpd8TCLsTtonJT6Wxv79r-b/s1600/eurotec_print_ad.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="600" data-original-width="424" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXkQ2O5ipKCBQWqaJOwBNYSXvO9t6dWkv-y4sh9ywYfHvVnodxec6N6klXFMHaWgv2Z51JSMge2OjegHv5WrRxXRU160kXuT1hs2fvBol203zIp6ds4zIoijpd8TCLsTtonJT6Wxv79r-b/s400/eurotec_print_ad.jpg" width="282" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Image from https://www.tonehome.de/eurotec/</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe8r567WigIvsKXvEb93rae4ozBppMFaE_KcjiWPEqkhHWOc-EidteujIctTp0C4verp9Vuxb_azDVmxXG_1hyphenhyphenk8qmFsZtyA6EMnvd9ZXpMRjOVN_r3S0_OGGJwYtGzFXKgJUFfWl0VIR_/s1600/faze.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1485" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe8r567WigIvsKXvEb93rae4ozBppMFaE_KcjiWPEqkhHWOc-EidteujIctTp0C4verp9Vuxb_azDVmxXG_1hyphenhyphenk8qmFsZtyA6EMnvd9ZXpMRjOVN_r3S0_OGGJwYtGzFXKgJUFfWl0VIR_/s400/faze.jpg" width="371" /></a></div>
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I have the phaser of the series, and it doesn't pass an effected signal. There are no schematics for this series that I could find online, but 4 JFETs and 4 opamps nearby give the game away - this is most likely a Phase 90 clone. The "React" knob seems to replace the mixing resistors for the clean and wet signals on the original so the phasing effect can be adjusted in intensity.<br />
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Build quality is a little cheap, but not unusual for the period - a single sided board that looks like a phenolic substrate. Traces will probably lift if overheated. The footswitch is unlike any I've seen before, it has a threaded black plastic cover to anchor itself to the enclosure. The enclosure is more like a sheet metal can than the usual diecast aluminium.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTo6ZxfN_7SiYDrkX09PV80cqvKk5qQEYCvXrYuY2BZNXS1DS5Qa1fdfsuvXO7G2UbHNOCN3OrUMDB5oAN5S29UMxCCcybYfDoE3JQkEgsSLZeVFqhfi1zxGKsqAp7p5RkT-PDy-RXyF1J/s1600/IMG_1011.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTo6ZxfN_7SiYDrkX09PV80cqvKk5qQEYCvXrYuY2BZNXS1DS5Qa1fdfsuvXO7G2UbHNOCN3OrUMDB5oAN5S29UMxCCcybYfDoE3JQkEgsSLZeVFqhfi1zxGKsqAp7p5RkT-PDy-RXyF1J/s400/IMG_1011.JPG" width="400" /></a></div>
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I went through this expecting to find some dead capacitors, but everything measured OK out of circuit. I did find one capacitor lead that had either broken loose from a cold solder joint or was never soldered in at the factory.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-rX19hyUqb_muOrjij7Xrini2Ckp51O5kbY7NP_-0Qg1iCCTMMINsgHiGy79hxNodWERNrHsuHOz7dSOCjx3qn3BjdfwhFtcypK9EIYIcge_5ZJonvS_PY9QT2LvILF6_UzGiAjZbZVue/s1600/IMG_1013.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-rX19hyUqb_muOrjij7Xrini2Ckp51O5kbY7NP_-0Qg1iCCTMMINsgHiGy79hxNodWERNrHsuHOz7dSOCjx3qn3BjdfwhFtcypK9EIYIcge_5ZJonvS_PY9QT2LvILF6_UzGiAjZbZVue/s400/IMG_1013.JPG" width="400" /></a></div>
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Feeding a sine wave into the pedal and probing the opamps showed that all had phase-shifted signals on the outputs except one - replacing this opamp restored the effected signal.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtuYHsjtrRo1eQ_5Ot4YP-auoQyMmGf8UxiWKCkMpTaqV0BZVQYZWdZeF8WghvG32wyMaFAg0qDtX8SLJUU2kHJPyHAOIR1AuU2OBLMd6CO4Czrz27KagrgSnXl1ZD3INj2DH5UvNvO9NI/s1600/IMG_1160.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtuYHsjtrRo1eQ_5Ot4YP-auoQyMmGf8UxiWKCkMpTaqV0BZVQYZWdZeF8WghvG32wyMaFAg0qDtX8SLJUU2kHJPyHAOIR1AuU2OBLMd6CO4Czrz27KagrgSnXl1ZD3INj2DH5UvNvO9NI/s400/IMG_1160.JPG" width="400" /></a></div>
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It really sounds great - the "react" control will dial the phasing all the way to a very resonant "thumping" sound - it can get much more extreme than the MXR originals.<br />
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<h2>
Adding external power:</h2>
Despite having an LED, there is no indication that the pedal is active when pushing the footswitch.<br />
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I found it interesting that the output jack on these boards are stereo, and the ring contact is tied to a diode that switches out the battery clip. Pictures of the original base station seem to show stereo TRS jacks, so it's possible that they supplied power through the additional conductor.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAt1e_t6n9Mo_wNiUkGZLHWNFI3jZPUffjEfg9HFFpVcLmTPnpYhtANoQ37meUWqim6Dz0aVN8ms1FzX-tc03FGCrPuaDA1eiR1RA1BfbiWLcNG3bC5x9wr7ZavDVXEtw394aJt9S0iN9E/s1600/cache_49461209.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="544" data-original-width="800" height="217" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAt1e_t6n9Mo_wNiUkGZLHWNFI3jZPUffjEfg9HFFpVcLmTPnpYhtANoQ37meUWqim6Dz0aVN8ms1FzX-tc03FGCrPuaDA1eiR1RA1BfbiWLcNG3bC5x9wr7ZavDVXEtw394aJt9S0iN9E/s320/cache_49461209.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Full modular system - image from https://www.tonehome.de/eurotec/</td></tr>
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I wired up a a mono 1/8" jack to a stereo 1/8" connector and added a 9V DC connector to the ring. When plugged into the output jack, the output signal is passed through and 9V power is used instead of the battery. As a bonus, the LED works as well.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwWlZu5jC75dfS8O1NMo7Hzaxh98zTW7OHB0fLZX07c4Fhlze0U_rB_Zw-2iis7wU8417MYJ8bKT5EYOrGmpTSZddI1htCY2zFsmGWGLI6PILjSECDuhOorAFfH9Vy5ZJuwA-TYkhZ5pwD/s1600/powercable.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="536" data-original-width="1600" height="133" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwWlZu5jC75dfS8O1NMo7Hzaxh98zTW7OHB0fLZX07c4Fhlze0U_rB_Zw-2iis7wU8417MYJ8bKT5EYOrGmpTSZddI1htCY2zFsmGWGLI6PILjSECDuhOorAFfH9Vy5ZJuwA-TYkhZ5pwD/s400/powercable.jpg" width="400" /></a></div>
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This seems like a worthwhile cable if you don't want to modify the enclosure.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com4tag:blogger.com,1999:blog-942832708593410658.post-75972129178619026862017-11-14T22:04:00.001+00:002017-11-18T20:25:27.557+00:00Digitech PDS 1000 & 2000 RepairsI am fond of the Dod/Digitech PDS series delays. On paper there's nothing too amazing - mid 1980s 8-bit delays with 1, 2 or 8 (if you can afford the PDS 8000) second maximum delay times. There are two features that win me over.<br />
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The first is the "Infinite Repeat" footswitch that locks the delay into a repeating loop. The loop can be pitch-shifted by changing the delay time, and when Infinite Repeats is turned off the delayed signal trails out like normal again. This is like playing with the shittiest looper and is a lot of fun, and surprisingly a lot of modern delays & loopers don't (or can't) do this. Some will repeat indefinitely without oscillating if the feedback is maxed (Boss DD series) but it's nice to have it on a dedicated switch, with feedback control available and ready for switching back to "normal" use. A surprising amount of 90s and early 00s delays can't smoothly pitch-shift recorded audio when playing with the delay times, and glitch or "jump" somewhere through the pot travel.<br />
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The second win is the internal design. The expected parts for a simple delay are all there - an ADC, a DAC, some memory and some logic gluing things together - but there are no custom ASICs, microcontrollers or programmable devices at all. Everything is done with standard CMOS logic. These delays could be built from scratch with new parts today, and they are very repairable. This is a little bit of a backwards approach for a 1985 era product - at this point Boss had already released the <a href="http://falseelectronics.blogspot.com/2017/08/boss-dd-2.html">DD2 </a>& DD3a delay pedals and they used the same ASIC from the Roland rackmount digital delays. This could have been a cultural difference, as Japanese manufacturers seemed to prefer going for custom ICs and offsetting the cost against using them in lots of products (<a href="http://falseelectronics.blogspot.com/2017/09/yamaha-dds-20m-delaysampler.html">Yamaha have also done this</a>). Digitech (or DOD at the time) may have to bring the series to market quickly, which could have forced them to use off-the-shelf parts. Whatever the reason, nearly ever part can be sourced pretty easily, unlike finding a replacement Boss controller IC from 1985 (good luck).<br />
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I repaired 4 of these delays recently. Here is a braindump:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuiWgG0dc9AF_FPWa0V08K7_mIMw7ddj1MPnAgRKsd4Bm7U5KRKOZR8Yki7KYzQCDZvjUlfgL9EzjXagclnE37K5BZilSvtb52X7e9vuvqIGCJ7h9n5BSIlNavkzXXFXONSlv942MNiGvA/s1600/pds_edit.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuiWgG0dc9AF_FPWa0V08K7_mIMw7ddj1MPnAgRKsd4Bm7U5KRKOZR8Yki7KYzQCDZvjUlfgL9EzjXagclnE37K5BZilSvtb52X7e9vuvqIGCJ7h9n5BSIlNavkzXXFXONSlv942MNiGvA/s400/pds_edit.jpg" width="400" /></a></div>
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PDS 2000 #1</h2>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvcejYcW3sGoGWxlx64id0sf7-acKskP54Y164FXnFFHV3N99jO29oQQh0Erdy-vVgMRro_HChWeVYMUCnoIyddhuXfHy3jvxLAeREE6hIelIAY8jWpNZb4yhldyNmzNJLGxKgoxfiAZPx/s1600/top.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1358" data-original-width="1600" height="338" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvcejYcW3sGoGWxlx64id0sf7-acKskP54Y164FXnFFHV3N99jO29oQQh0Erdy-vVgMRro_HChWeVYMUCnoIyddhuXfHy3jvxLAeREE6hIelIAY8jWpNZb4yhldyNmzNJLGxKgoxfiAZPx/s400/top.jpg" width="400" /></a></div>
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All of the pedals in this series came with snap-in plastic battery doors that are not held captive by the enclosure (i.e. they are removable). This means they get lost, and I have never actually seen one.</div>
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This PDS 2000 (mine) was fairly easy to deal with. It's a 2 second delay that adds sampling modes that can trigger the delay sample by a footswitch or an external trigger signal. It had some broken wires in the harness between the PCB and jacks/switches. I think this is due to using the pedal with a battery but without a battery door - the weight of the battery pulls on the wiring if it's free to swing around on the end of the battery clip. This just needed some soldering to bring it back.</div>
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The footswitches were also unreliable, so I replaced the microswitches. More on that below.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0wCuVrTjZER5iQ44wrtL8R9Hh9sEzSHbwcxAfjKIYlUWQyGt-0PLmY8xQjITJoj8lQ-azG-niGPOsyySdq5LXNhybdcwySMmqFapTS4pkSldPnVx0H3MlFS76EhFVve-fYS7lLSE_ms8a/s1600/guts.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1317" data-original-width="1600" height="328" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0wCuVrTjZER5iQ44wrtL8R9Hh9sEzSHbwcxAfjKIYlUWQyGt-0PLmY8xQjITJoj8lQ-azG-niGPOsyySdq5LXNhybdcwySMmqFapTS4pkSldPnVx0H3MlFS76EhFVve-fYS7lLSE_ms8a/s400/guts.jpg" width="400" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyUNdmxhGOtxADz7vO0v1JyPCJevepIYV8fVx4yKiqgK9eS8CkhckQOMeR2-xCAoexB4jNUDCthXXtXPXkvRaqQu22HZHZl3ae_Z_ft08RXI7PTeRBPeLOXP4PsJmwEJU994pGOet77yCh/s1600/guts2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1283" data-original-width="1600" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyUNdmxhGOtxADz7vO0v1JyPCJevepIYV8fVx4yKiqgK9eS8CkhckQOMeR2-xCAoexB4jNUDCthXXtXPXkvRaqQu22HZHZl3ae_Z_ft08RXI7PTeRBPeLOXP4PsJmwEJU994pGOet77yCh/s400/guts2.jpg" width="400" /></a></div>
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In an unusual move, DOD actually sprang for a silkscreen print on this PCB. Schematics are available online but can be hard to match them with a PCB when there is no silkscreen and no part designators.</div>
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PDS 1000 #1</h2>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyhFXtpAZdD6X7j2PmRoUzkjWBmcmOfPSuu2jelc8PMfki0-tfdtIw6ShLzDjQqJt1P6fPGfYztqkv6g9u0eu0r2yZ6QZiZoW8-coQsEh-UfbtE_CwNRAGoNVGysi76blwjTP8ztWrQvie/s1600/top.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1255" data-original-width="1600" height="313" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyhFXtpAZdD6X7j2PmRoUzkjWBmcmOfPSuu2jelc8PMfki0-tfdtIw6ShLzDjQqJt1P6fPGfYztqkv6g9u0eu0r2yZ6QZiZoW8-coQsEh-UfbtE_CwNRAGoNVGysi76blwjTP8ztWrQvie/s400/top.jpg" width="400" /></a></div>
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This one was partially working when I got it. The output jack wouldn't hold a cable in, the footswitches rarely worked and the delay length maxed out about 75% of the way through the pot's travel - but it did work as a delay. I replaced the footswitches and bent the retaining lug on the output jack (I may go back and replace this) so that it was a usable effect.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRqfQ6yaQkxzXdkCogXfnk2BI3bvRVCTbYqAzgm6TPwokUMoZMfJhu2RfxfT6WAdSawBA4rx3E9KS4YaVPHtTgQgcoSJ-W5NThwOStQn0ptxHBCOUPhiQ_2v1vMBOEhSO50eOzaMvKGngA/s1600/guts.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1300" data-original-width="1600" height="323" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRqfQ6yaQkxzXdkCogXfnk2BI3bvRVCTbYqAzgm6TPwokUMoZMfJhu2RfxfT6WAdSawBA4rx3E9KS4YaVPHtTgQgcoSJ-W5NThwOStQn0ptxHBCOUPhiQ_2v1vMBOEhSO50eOzaMvKGngA/s400/guts.jpg" width="400" /></a></div>
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I have never seen a PDS 1000 schematic, but the PDS 1002 2 second version looks like it's very similar. The delay time control circuit is shared across the earlier series. Delay time is varied by changing the frequency of the main clock signal that shifts digital samples into and out of DRAM memory. Faster clock frequencies shift data faster and give shorter delays. Delay time is adjusted by 3(!) potentiometers, the delay time pot on the front of the enclosure, a trimpot that adjusts range of the of the main delay time pot, and a final trimpot that globally adjusts clock frequency by small amounts. You don't really get a very wide range of adjustment so trying to get longer delays by tweaking pots might not work too well.</div>
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Tweaking these delay pots brought the delay back to 1 second and adjustable through the full range of the delay pot.</div>
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PDS 2000 #2</h2>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcjtBxM_-HUQmX8HtsB1gH4KtAotjVRdOhsRqkw9OuECn-nADcMH2u8o0U79ANEwrEWrGv66WGpLrT8LQ0ONjkSKhXdiz8IzbOGwt7mzIHnU5vgQmiMw8_4dYaem8qxKJ-U8V1R0IUqbWB/s1600/top.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1297" data-original-width="1600" height="323" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcjtBxM_-HUQmX8HtsB1gH4KtAotjVRdOhsRqkw9OuECn-nADcMH2u8o0U79ANEwrEWrGv66WGpLrT8LQ0ONjkSKhXdiz8IzbOGwt7mzIHnU5vgQmiMw8_4dYaem8qxKJ-U8V1R0IUqbWB/s400/top.jpg" width="400" /></a></div>
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This is the only pedal of the 4 that didn 't power up at all. None of the logic chips had any sensible voltage at the VCC pins, but the opamps were getting 9V. There is a 78L05 to drop the 9-10V input down to power all the logic chips, and this has a JFET soft-start circuit that ramps up the 5V power supply, presumably to protect the digital chips from a loose or intermittent power cable. I replaced the timing cap with no luck, then swapped the FET for a new J201 and it powered up.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCqKwCaTzR4qLeqHnDlZnEivnSqYxkjezyeSPiV-WaaJ-HImya_JAsNQT01v1eZWIKr5qrzpV3WeCNCmjthtMYC44kFsFAr4EAmdsj2wIsSX9hORKCcS2nQyARTq5O5XStj3v2_Wy0_AH_/s1600/softstart.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="499" data-original-width="658" height="302" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCqKwCaTzR4qLeqHnDlZnEivnSqYxkjezyeSPiV-WaaJ-HImya_JAsNQT01v1eZWIKr5qrzpV3WeCNCmjthtMYC44kFsFAr4EAmdsj2wIsSX9hORKCcS2nQyARTq5O5XStj3v2_Wy0_AH_/s400/softstart.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This a soft-start for the 9V supply on the PDS1002. The 2000 has something similar.</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs0wa7FdNzIcGMDTMoE0HktrNWDq55RE-VV5SpBTZJG1DJRFEMcchKvHVzDwCuMWQrLz-NTCXALQFQGDRH4s8TquBhdyM0ADig7zfB63s5yCXbh8mamtb68BunzkYBIwc5hIetrczjiquX/s1600/pcb.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1324" data-original-width="1600" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhs0wa7FdNzIcGMDTMoE0HktrNWDq55RE-VV5SpBTZJG1DJRFEMcchKvHVzDwCuMWQrLz-NTCXALQFQGDRH4s8TquBhdyM0ADig7zfB63s5yCXbh8mamtb68BunzkYBIwc5hIetrczjiquX/s400/pcb.jpg" width="400" /></a></div>
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Everything seemed to work, except that I couldn't change delay ranges, it was stuck on the longest range (2 seconds). The sampling modes also weren't quite right, trying to trigger samples would switch the pedal into bypass mode or sometimes do nothing at all. I traced signals back from the delay range switch to a 74HC04 hex inverter, which looked dead. I swapped this chip over from the other 2000 and it worked. I ordered a new 74HC04 and got two working pedals.</div>
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This one also was not quite a 2 second delay so I did some pot tweaking. Unfortunately I managed to slip with an oscilloscope probe and shorted two pins on the DRAM chip, and killed an input pin. I replaced with a TMS4256 DRAM from eBay - works fine. With the new chip the delay rates could be carefully dialled in to 2 seconds pretty quickly.</div>
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PDS 1000 #2</h2>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiryjj8L9Z9JRHYqBJGi4t74Z2Eo6MLYgd1ikzf69GVc4FV7AHYxCCOu6aAO3bYo_JTyf8YdyfO-MokHkt1HB9EJXjrcnnlfGjJSdpCjB9igaz1nbhhE3NoEnut3ntfUChR_t6kSxGqwKNj/s1600/pds1000.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1304" data-original-width="1600" height="325" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiryjj8L9Z9JRHYqBJGi4t74Z2Eo6MLYgd1ikzf69GVc4FV7AHYxCCOu6aAO3bYo_JTyf8YdyfO-MokHkt1HB9EJXjrcnnlfGjJSdpCjB9igaz1nbhhE3NoEnut3ntfUChR_t6kSxGqwKNj/s400/pds1000.jpg" width="400" /></a></div>
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This was in the worst condition. I got this in a box of failed repairs from a music store in the US some years ago and never did a lot with it until now. Someone had already taken a crack at fixing it, it was missing knobs and a back panel. Two of the pots were broken, the bodies would wobble freely against the legs as if they had detached internally. The 1Meg trimmer for clock frequency was also broken off.</div>
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I replaced the trimmer and set it to the middle of the it's range, based on how the other 1000 was set. The PCB mount pots were a little harder, DOD use Alpha pots marked "W" which I don't think are actually W taper (W taper is logarithmic for half the travel, then reverse log for the other half). I replaced with long-leg alpha pots. The replacements are a little taller than the originals, so I cut the legs a little shorter and soldered some bus bar to them, then soldered the bus wire into the PCB. This actually worked pretty well, but replacing these pots and running wires to the PCB is probably a better long-term solution.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBy5TmYBjw7bQHxNZshNScBl1ai3Zeub0D7bmQmdpdEtbVN4sgz3hZ-lGNnc2A_ir95ryMnSiucgXGPx0ShOiAveVP9-5ye0EOozckuIKeFh8EzWrvTmWduS8BCQ0K5RSa2kYYnCWm3kll/s1600/IMG_0907.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBy5TmYBjw7bQHxNZshNScBl1ai3Zeub0D7bmQmdpdEtbVN4sgz3hZ-lGNnc2A_ir95ryMnSiucgXGPx0ShOiAveVP9-5ye0EOozckuIKeFh8EzWrvTmWduS8BCQ0K5RSa2kYYnCWm3kll/s400/IMG_0907.JPG" width="400" /></a></div>
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After replacing pots I found that delay time wasn't working because of broken trace, I ran some Kynar wire to restore it. The mix knob didn't work and it was stuck at 100% wet - this turned out to be another bad JFET. </div>
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At this point things appeared to work again, except the delay was very distorted and noisy. I messed around with compounder trimpot as I thought that may be distorting - no improvement. Eventually I realised that bad memory chips would give corrupted repeats which would probably sound like distortion, so I swapped the DRAM from the other PDS 1000 and it worked. I ordered some replacement DRAM (I used MK4564) and they worked just fine.</div>
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Adjusting delay time</h2>
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There may be an "official" method for adjusting maximum delay length using a testpoint on the PCB but without a service manual I've come up with my own.</div>
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The capacity of DRAM can be looked up from the P/N and the nominal maximum delay in seconds is known. My reasoning is that DRAM should be completely filled in this time, so I probe the DRAM with an oscilloscope and adjust delay length until the frequency of data in and out matches the DRAM size divided by nominal delay length in seconds.</div>
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For the 2000 the DRAM is 262144 memory locations and max delay is 2 seconds, so I want data to be going in and out of memory at around 262144/2 times per second or 131072 Hz when the delay pot is all the way up. This can be measured from the DRAM Write Enable pin, and probably from the Data in and Data out pins as well. Most of the tweaking is done on the lower global clock frequency trim, usually after making sure the delay pot is working throughout it's whole range. Sometimes I had to iterate and go back and forth between the two sets of pots. Adjustment on trimpots is fairly coarse, so this can't be dialled with really great precision but I find it much easier than trying to listen to the delay and sync to a stopwatch or something similar.</div>
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Modding for more delay time</h2>
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There are online discussions about modifying these pedals for longer delay times that usually involve tweaking the delay pots away from nominal positions to get longer delays. I think this will only work well for very lo-fi sounds, as the sample rate will get much lower and aliasing effects will get worse.</div>
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The delay loop in the PDS series is basically some 4040 ripple counters counting through memory addresses and resetting when the end of memory is reached. A better approach to extending delay time is replacing DRAM with a larger IC (or multiple ICs) and adjusting the counter reset logic to address the larger memory. I have some spare DRAM for both of these pedals so I would like to try this.</div>
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I haven't seen a schematic for the PDS 8000 (8 second delay). I would like to see how this was implemented, as it should have 4x the memory of the PDS 2000. Extending the 2000 to 8 seconds may be possible depending on how extensive the differences are.</div>
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The best picture I can find online shows a single 18 pin (not 16 pin) IC, but the label isn't legible. Presumably it's a 1Mbit x 1 DRAM.</div>
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Please let me know if you have a PDS 8000 schematic or high-resolution board shots.</div>
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There is a PDS 20/20 delay schematic available (<a href="http://www.experimentalistsanonymous.com/diy/Schematics/Delay%20Echo%20and%20Samplers/Digitech%20PDS2020.pdf">http://www.experimentalistsanonymous.com/diy/Schematics/Delay%20Echo%20and%20Samplers/Digitech%20PDS2020.pdf</a>) which uses 2 4464 DRAMs, which is twice the memory of the PDS 2000 but still only does a 2 second delay. <a href="http://www.americaspedal.net/">America's Pedal</a> has a catalog for the <a href="http://www.americaspedal.net/fxlit/cat/pdslist1286_2.jpg">PDS series</a> which explains why - the 20/20 has a delay signal bandwidth of 16 kHz, the rest of the series only has 7 kHz except for the PDS 1700. I am guessing the higher sample rate is for the chorus/flanger modes where really short delays are needed.<br />
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<h2>
Footswitches</h2>
Dod used a fairly cheap mechanical design for actuating footswitch buttons on a small PCB. The plastic foot panels are cantilevered and are returned to their neutral position by a spring at the "fixed" end, not the free end which would make more sense. There is also no real end-stop to limit the force on the footswitch - if you stomp hard you will crush the button. This is problematic as most players will stomp harder if the switch doesn't work, so once they start to fail they deteriorate quickly.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh20O_YaSAXdSNozKMrLlu4yP2mXhl31L_rcQNPsW7ucqx15r2lB5_dI6dV6x7Rvh6zKEnoHxUr3FqlLdlvKApfF99Dg5zN4n30mVv8KA3Ws0AXZJfPLJX-h6lMFMLB5rF22K7F5bqjiz4Y/s1600/IMG_0501.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh20O_YaSAXdSNozKMrLlu4yP2mXhl31L_rcQNPsW7ucqx15r2lB5_dI6dV6x7Rvh6zKEnoHxUr3FqlLdlvKApfF99Dg5zN4n30mVv8KA3Ws0AXZJfPLJX-h6lMFMLB5rF22K7F5bqjiz4Y/s320/IMG_0501.JPG" width="320" /></a></div>
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There is advice online on adjusting spring tension to get a pedal to switch more reliably. Don't bother. If a DOD pedal does not switch every time, just replace the 10mm button on the PCB. They are very cheap and should last another decade of use. Play with the mounting hardware only if the levers aren't rotating correctly.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com33tag:blogger.com,1999:blog-942832708593410658.post-46546534601703646872017-09-05T18:55:00.001+01:002017-09-05T19:03:40.441+01:00Yamaha DDS-20M Delay/SamplerI wouldn't really think of Yamaha as a guitar pedal company. They have made a lot of classical instruments, drum machines, e-drums and studio gear (I have an SPX90 I really need to repair) so I guess the pedigree is there. This is a mid-80s 2 second digital delay/sampler, from that period when putting "sampler" on products must have excited guitar players.<br />
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The mechanical design is a little different - all of the controls are recessed at a height below the footswitch and there is a "unibrow" along the top with the logos and LED.<br />
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There are no schematics and not a huge amount of info on these that I could find online, other than there was a range of pedals in this form factor. No signs of life.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuU0mgcBs1mXzqUbtA9EuYugVraTK8pbz8lfijnGuifJmrWdo7CzIoLSPs5C6nbcciJfUawfMDKNGDCu6x2lS-0EnOd7mi-bmPjhSY3AcUqa8ANl74JPTvXSbmBEYEmjYCQgHwVCtpgHo7/s1600/dds20m.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1140" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuU0mgcBs1mXzqUbtA9EuYugVraTK8pbz8lfijnGuifJmrWdo7CzIoLSPs5C6nbcciJfUawfMDKNGDCu6x2lS-0EnOd7mi-bmPjhSY3AcUqa8ANl74JPTvXSbmBEYEmjYCQgHwVCtpgHo7/s400/dds20m.jpg" width="285" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQS9ebR7UAiFSSePlLbUv5E35t9NiW55l1Z2x-HNXFJxgH17HBGQX7-We7ntJACtcjIvpgh0TOkSjud2b9Ss0Iq2ExPT66z97ILMNETEJUG3X2SGMQVaE5HzsJGDTSS2j1UAhyphenhyphentlI-f_XJ/s1600/back.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1107" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQS9ebR7UAiFSSePlLbUv5E35t9NiW55l1Z2x-HNXFJxgH17HBGQX7-We7ntJACtcjIvpgh0TOkSjud2b9Ss0Iq2ExPT66z97ILMNETEJUG3X2SGMQVaE5HzsJGDTSS2j1UAhyphenhyphentlI-f_XJ/s400/back.jpg" width="276" /></a></div>
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After looking on the inside, I got the impression that someone else had attempted a fix. There was a resistor between the +9V and ground pads of the DC jack (?), the ground trace had been cut in two places for some reason and a wire had been soldered in to replace it. I can't see why the resistor between 9V and ground would be needed for anything other than wasting power, so I removed it. I also found that the ground from the DC jack was not connected to circuit ground. Adding a jumper was enough to get this to fire up with a DC supply, but not with a battery. It's possible that the resistor was originally connected between jack ground and circuit ground but as it was several kilo-ohms a wire would be a better solution.<br />
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The pedal uses a 2 board design, connected together with wires. Both are single-sided PCBs that look like a phenolic paper material and no through-hole plating anywhere. This is pretty typical for 80s Japanese electronics but it can mean that any board-mounted hardware can be fragile as there is only solder on one side of the board anchoring it place. In this delay, the output jack had taken some force (probably a cable was stepped on) and the pad to the jack tip had broken, this had to be re-soldered to get an output signal. One of the PCBs has most of the analog parts, the inner one has the digital controller and the pots and rotary switch.<br />
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<tr><td style="text-align: center;"><img border="0" data-original-height="1600" data-original-width="1079" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQI5JWCQlT9qKgoluYH58T6TDZz9kgJuMhNP0igkte1tWx5WCdq0zof_BJVHENXMvfP2xl2ynP8o4Kq73wyJqjZuCviwG6f3mi6FwuTNnolykHgkZveb1-QcDU1w7fbHjys8fnMkzbmlMu/s400/fixed.jpg" style="margin-left: auto; margin-right: auto;" width="267" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;">2 wires added and a diode replaced</td></tr>
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It still didn't work from a battery. Following the (broken) ground trace to the other side of the board I could see that a diode was used to switch out the battery when a power supply was used, replacing this diode fixed everything.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2DDqR8S1te9Up8Druhompk9aS4eKB6Sb66cgwi43AvUKLJv_BGBxZoFr_7ZnTbMqIQYr9X8rAR0WsojBpmoDthyy_v-7fOR0Ccz4uwmoXm5esNRCNJV1etHetG1FIyE1C8eGqAB6EzAqk/s1600/IMG_1223.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj2DDqR8S1te9Up8Druhompk9aS4eKB6Sb66cgwi43AvUKLJv_BGBxZoFr_7ZnTbMqIQYr9X8rAR0WsojBpmoDthyy_v-7fOR0Ccz4uwmoXm5esNRCNJV1etHetG1FIyE1C8eGqAB6EzAqk/s400/IMG_1223.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Analog board, component side</td></tr>
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The analog board has a 4066 for bypass/effected switching, 5534 opamps, a Motorola M5218 audio pre-amp (I have only seen this part in Japanese pedals, I think the original Boss DS-1 used something like this), <span class="_Tgc">μpc1571 compander (NEC's NE571 clone) and the chip in the bottom left corner is an LM311 comparator. The comparator is forming part of a sigma-delta ADC with the digital controller, much like the Boss DD-2 and the Digitech PDS series of delays.</span><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCd4Qeh9_9hDbGeWCAY3F_OUxRfZh039EV53Y-J3IxN2KeuWtUnTkfrmCUtipbrKAAsekfogNHpbV5EA5Wrui2yU8rEk1XnjMZKZJhkWsZm5VJxNf2CPNdBHalm1y2Z16hc4-KFlJ2fiBn/s1600/IMG_1224.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCd4Qeh9_9hDbGeWCAY3F_OUxRfZh039EV53Y-J3IxN2KeuWtUnTkfrmCUtipbrKAAsekfogNHpbV5EA5Wrui2yU8rEk1XnjMZKZJhkWsZm5VJxNf2CPNdBHalm1y2Z16hc4-KFlJ2fiBn/s400/IMG_1224.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bizarre vertical component assemblies</td></tr>
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<span class="_Tgc">I thought the parts marked "< RIVER < RIVER" were SIP ICs, but they are actually components standing vertically! They seem to be clamped together at the top. I don't know if there was automated machines to produce these assemblies or if they were re-used in other designs but it's surprising that this was cheap enough to be worth the effort.</span><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1bKsSaQhiho1vSJq6vGcBVbzl3IuR6XUaXkC5ZCXcE_A7Z-MG7JUAcXulldfNbMNHGmUDmevhs20uoJy6nYhQVSSLqmz6bk2e8zN9hqugXSEdAKKjEYzRJv6d8I_fL_W_MGBekxFtYjEg/s1600/IMG_1218.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1bKsSaQhiho1vSJq6vGcBVbzl3IuR6XUaXkC5ZCXcE_A7Z-MG7JUAcXulldfNbMNHGmUDmevhs20uoJy6nYhQVSSLqmz6bk2e8zN9hqugXSEdAKKjEYzRJv6d8I_fL_W_MGBekxFtYjEg/s400/IMG_1218.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Digital board</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
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The digital controller is an "M654131". No info on this, probably a Yamaha custom. Maybe they used it somewhere else in a different product. I don't have any pictures of the back side of this board so I don't know what type of memory is used. It looks like there are two 9-pin SIPs connected straight to the controller so I would guess 2 64k DRAMs, assuming this is an 8-bit delay.<br />
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It sounds great. I like that these early digital designs use companders and have simple master clock signals. It's like a holdover from the days of analog delay designs. This one can pitch-shift the delay signal smoothly, unlike some more modern delays.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com4tag:blogger.com,1999:blog-942832708593410658.post-244003385722901842017-08-27T17:21:00.002+01:002022-10-05T15:21:04.825+01:00Boss DD-2/DSD-2 repairs<div>
Once again, I have a backlog of photos of things with very poor notes - hopefully I haven't forgotten everything.<br />
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<h2>
Early Boss Delays</h2>
I've played a few of the early Boss delays, but oddly enough I've had none of the more common modern versions (DD-5/6/7 etc). The DD-2 is regarded as the first digital delay in a stompbox, using some of the tech from Roland's larger rackmount delays (see Boss's article on<a href="http://www.bossus.com/blog/2015/11/11/echoes-in-time-the-history-of-boss-delay-pedals/"> the history of delays</a>). The architecture is similar to early Japanese delays, with one large custom controller IC doing all the digital work - a sigma delta ADC (with an external comparator), DRAM interfacing & parallel outputs for an resistor network DAC. This is the same RDD63H101 custom used in the famous Roland SDE-3000, often referred to as the "long chip" as it barely fits in the Boss stompbox case. Everything is synchronised off a single master clock which is directly controlled by the delay time knob - changing the delay time smoothly pitch-shifts whatever audio is memory without any glitching.<br />
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<tr><td style="text-align: center;"><img border="0" data-original-height="795" data-original-width="1211" height="262" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbyPW_8pDySsjXjMXf6uMpfTrtpilJQ-sc-zp-yIEsr6bGo6DQGsrWly6u_49OYZ3yoFGcxhdhakeoU_gAIjG_5U-qFsNRTte1KWsgDx1BQ53ZfX4zwmqgIQvY6eIBrXQuTcdyoClw3ulR/s400/controller.png" style="margin-left: auto; margin-right: auto;" width="400" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Digital section, from Boss Service Notes</td></tr>
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Unlike many other 80s delay pedals, the audio is quantised to 12-bit samples (8 is more typical) for lower noise and there is also more memory than I would expected, 3 64k DRAM chips (a single 64k IC is common in some 1 second digital delays from the era).<br />
<br />
Parts of the schematic look more like what would be expected from an analog delay, there is a NE570 compressing on the way into the digital delay line and expanding on the way out to further help with noise, and pre-emphasis and de-emphasis filters at 7 kHz to hide any sampling bandwidth limitations.<br />
<br />
The custom chip is also a weak point in repairing these. If it's dead then the only way to find a replacement is to pull one from another pedal. I am hoping that most of these are still working and that faulty pedals just have power or memory issues.<br />
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<h3>
DD-2 #1</h3>
This was another eBay purchase. It powered up, but only produced a whining noise. The noise would change in volume with the Level knob and change in pitch with Delay Time knob, so the digital end was the first suspect. Power from the 5V regulator looked good.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGVgVcZdoWGpmqx4CX0I7PFbC4lQYK8b9dTlol51gtBQbqcUCXtQWjKxJPTzgYXjx98ROBBbIA7Bapxyam0h7BsnNoUzQK7ICvuI6zMQJ2yhu34ov64nq6gQa9anPeeZNQRaeJ5zrFSgaE/s1600/dd2_1.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1075" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGVgVcZdoWGpmqx4CX0I7PFbC4lQYK8b9dTlol51gtBQbqcUCXtQWjKxJPTzgYXjx98ROBBbIA7Bapxyam0h7BsnNoUzQK7ICvuI6zMQJ2yhu34ov64nq6gQa9anPeeZNQRaeJ5zrFSgaE/s320/dd2_1.jpg" width="214" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DD-2 #1</td></tr>
</tbody></table>
<br />
I had seen something like this before on an 80s Digitech PDS delay (write-up to come at some point in the future). In that case I was getting massively distorted repeats and I narrowed things down to bad memory, data was beings written in but garbage was being read out. I also knew that <a href="http://spectrum.ieee.org/computing/hardware/drams-damning-defects-and-how-they-cripple-computers">DRAM failure was very common in the late 70s/early 80s</a> so I decided to try swapping out new memory chips on this DD-2.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtWlO8hOJB5iBR66PBnZ2AXIJDfsYeVpvbIGqcmgU0zW35j7I1WaWt6wfBAogzNWSz5ehj3pDk-o6kFybI68XXGwPJVOZcCEOBEYOfPHmb2WGB14XUG7x2FNTCKylXGJWvwHfFpJOxHkZT/s1600/IMG_1147.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtWlO8hOJB5iBR66PBnZ2AXIJDfsYeVpvbIGqcmgU0zW35j7I1WaWt6wfBAogzNWSz5ehj3pDk-o6kFybI68XXGwPJVOZcCEOBEYOfPHmb2WGB14XUG7x2FNTCKylXGJWvwHfFpJOxHkZT/s400/IMG_1147.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All memory ICs desoldered</td></tr>
</tbody></table>
The 3 DRAM ICs are directly below the main controller. These pedals are <i>absolutely crammed </i>with through-hole parts, it's impressive that so much could be fit into the standard BOSS housing when you consider how much more simpler the earlier Boss pedals were in comparison.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFMtFVExPe0naVl86E0YgBd8wn8Dbbb1pSNLZaIm_H49QXkOJn51hyphenhyphenuPWvMqHm5K68i6WtqBkfTx18dsB3_XJ8FypXZ-FQg2EYIb1BrY9TSh_EDsU1Opm94fYRk8ckhmhOyYUl9RwJC6-e/s1600/socketed.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1368" data-original-width="1600" height="341" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFMtFVExPe0naVl86E0YgBd8wn8Dbbb1pSNLZaIm_H49QXkOJn51hyphenhyphenuPWvMqHm5K68i6WtqBkfTx18dsB3_XJ8FypXZ-FQg2EYIb1BrY9TSh_EDsU1Opm94fYRk8ckhmhOyYUl9RwJC6-e/s400/socketed.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Socketed memory ICs - a dead end.</td></tr>
</tbody></table>
<br />
Initially I tried to install sockets to make troubleshooting easier. After a struggle to get socket into the board I realised this wouldn't work, the flying leads over ICs would need to replaced with longer wires and it was possible the PCB wouldn't fit back inside the case. <br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpNnkpOvPH5Fd9b-D39oxCTQ4HNG62woYmZ6bs0uN_iQw9crXF8rsvEe1p-OpjMD73nMdNmWFgbN5eGv_0NZLXQG1eCkq3nwh69b0CHbASU9ANNg1sHgQ4y6YARUTNnUlUIGx7XABBkCkX/s1600/new_ram.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1391" data-original-width="1600" height="347" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpNnkpOvPH5Fd9b-D39oxCTQ4HNG62woYmZ6bs0uN_iQw9crXF8rsvEe1p-OpjMD73nMdNmWFgbN5eGv_0NZLXQG1eCkq3nwh69b0CHbASU9ANNg1sHgQ4y6YARUTNnUlUIGx7XABBkCkX/s400/new_ram.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Replacement memory installed.</td></tr>
</tbody></table>
<br />
I removed the sockets and installed 3 MK4164 64K DRAMs with a compatible pinouts. Switched the pedal on - absolutely nothing had changed. Shit.<br />
<br />
Going over the each pin of the controller IC with an oscilloscope, I found that even though 5V was present, when I had a test signal connected to the input (a triangle wave in this case) I could see the triangle wave riding on top of the 5V supply! I traced this back to a cracked solder joint on the 5V regulator, which was then reflowed. The power filtering electrolytics were replaced at the same time. Another delay working again.<br />
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<h3>
DD-2 #2</h3>
<br />
This much dirtier DD-2 was not mine, but was bought broken at a market for €5(!) and eventually found it's way to me to take a look.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQrO7tb15xm5gatq6yB7-Ol89xn3pHhBt90uFCvD9NwH9MIc8ti4_cg-9anfcCs6XMFzoPm-iaX1inPGMBI9DpSU8b-I3I06HCoshjKdRqNHYv2gE9ok5nZeWHfp55uj2_OiVB_TPUvi8d/s1600/dd2_2.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="988" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQrO7tb15xm5gatq6yB7-Ol89xn3pHhBt90uFCvD9NwH9MIc8ti4_cg-9anfcCs6XMFzoPm-iaX1inPGMBI9DpSU8b-I3I06HCoshjKdRqNHYv2gE9ok5nZeWHfp55uj2_OiVB_TPUvi8d/s400/dd2_2.jpg" width="246" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DD-2 #2</td></tr>
</tbody></table>
<br />
This was a lot easier to figure out, the pedal wasn't lighting up and was shorting out my power supply. The reverse polarity protection zener diode (D6) was burnt out and failed as a short. It looked like someone had been in here before and had tried to jumper over a PCB track with a piece of wire and some cold-looking solder joints.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7yNAuIx5ABsGoeExU_swv3VfgjS55VRzabTeK3CdP5ASC-jgt5pMQ_ZClxIwN5vZ1ZWLlN0o6pBNixI_C_FRk-p4VxTt68k0ROz2LjJqElntpd0iPTSX8RCdWlav-mxSN2HurmV1y1rIt/s1600/og_jumper.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1535" data-original-width="1600" height="382" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7yNAuIx5ABsGoeExU_swv3VfgjS55VRzabTeK3CdP5ASC-jgt5pMQ_ZClxIwN5vZ1ZWLlN0o6pBNixI_C_FRk-p4VxTt68k0ROz2LjJqElntpd0iPTSX8RCdWlav-mxSN2HurmV1y1rIt/s400/og_jumper.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Previous attempt at a fix</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: left;">
After removing the jumper and the diode (which tested as a short out-of-circuit) the board looked a little rough. I added a 1n4001 as a replacement and tried it out.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6s9D0Sg4rwenO-ofenT0dbC1oaa8sUJmhIf_wW5XqpyJg7iMUWVjnhaSqRtOrtCAO-U7TbOwyoaefcVT8f3jTYqSdNquBP4aiKgwTnxyPtLp29TcOCChtG0J9dDZXFegKofELtbLJACQK/s1600/IMG_1117.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6s9D0Sg4rwenO-ofenT0dbC1oaa8sUJmhIf_wW5XqpyJg7iMUWVjnhaSqRtOrtCAO-U7TbOwyoaefcVT8f3jTYqSdNquBP4aiKgwTnxyPtLp29TcOCChtG0J9dDZXFegKofELtbLJACQK/s400/IMG_1117.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Some PCB foil damage</td></tr>
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This time the LED would only come on when the pedal button was held down, it wouldn't latch and stay on. Usually Boss use a discrete flip-flop for switching (an excellent <a href="http://www.geofex.com/Article_Folders/bosstech.pdf">Geofex article </a>on this) but in the DD-2 they use a <a href="https://shop.strato.com/WebRoot/StoreES2/Shops/62070367/MediaGallery/Datasheets/BA634.pdf">BA634</a> flip-flop in a SIP package, probably just to save some real estate on the PCB. I thought this IC was bad but it just had a broken ground trace - another small jumper wire fixed it.<br />
<br />
Both of these pedals sounded identical, and when I checked the calibration routines in the <a href="https://drive.google.com/file/d/0ByVCt2OFhXnyNlpMM1pEdkVQcTA/view?usp=sharing&resourcekey=0-_fHDj53wBco-i3huZQHKbw">service manuals </a>they were both still perfectly dialled, with max delay coming in at 800ms on both.<br />
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<h3>
Bonus Repair: Boss DSD-2</h3>
This pedal is a couple of years newer. The problem was pretty obvious, all of the 1/4" jacks and the DC power jack were broken and had to be replaced. I can only guess someone was putting the pedals into a bag without unplugging the cables and they managed to break them all.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_9nFzQOzsueTAu9n32EPiPheNMaB70FXywR-FRt2URWdTLoeTNOPq19eUZzodva1cDL9956IfJPMOh5Irvv_jNHWxHDqiVjIEQljSL1CuKIQ89u9s_Apjol2BIgM6FZauu1KLHYiQrGHw/s1600/dsd2.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1061" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_9nFzQOzsueTAu9n32EPiPheNMaB70FXywR-FRt2URWdTLoeTNOPq19eUZzodva1cDL9956IfJPMOh5Irvv_jNHWxHDqiVjIEQljSL1CuKIQ89u9s_Apjol2BIgM6FZauu1KLHYiQrGHw/s400/dsd2.jpg" width="265" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DSD-2</td></tr>
</tbody></table>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZ9yIMQQHHuSxPk8rBNaIZqR3eHerDIyXtx_f39qz7N5RwQPEE219mKqWuZdDilYAkWSgkBcAcKDppXIE3y0CVYNgKc_wFALjJsSX9lZLWA-QJVSaRl7EIWIFY1joIcfqL8ZFxxFSsLRxQ/s1600/guts.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1309" data-original-width="1600" height="261" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZ9yIMQQHHuSxPk8rBNaIZqR3eHerDIyXtx_f39qz7N5RwQPEE219mKqWuZdDilYAkWSgkBcAcKDppXIE3y0CVYNgKc_wFALjJsSX9lZLWA-QJVSaRl7EIWIFY1joIcfqL8ZFxxFSsLRxQ/s320/guts.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Guts - note broken jacks everywhere</td></tr>
</tbody></table>
<br />
What is interesting is how close the DSD-2 is to the DD-2. There are a couple of part changes for cost and space savings (the RAM chips have been replaced with SIP packages that are a better use of space) but it's basically the DD-2 without the hold mode and with an external trigger input instead as a "sampler" mode. The <a href="https://drive.google.com/file/d/0ByVCt2OFhXnyeS1RQWFlUlpWRTA/view?usp=sharing&resourcekey=0-RptiqID9l1iZwVttQIYsyA">service notes</a> even shows that the only differences in the digital side is that a couple of pins are wired differently on the controller to trigger a delay from the Trig In jack instead of the footswitch.<br />
<br />
The DSD-2 should perform identically to the DD-2 in delay modes, and to my ears they sound identical. If you like this sound it may be worth finding a DSD-2/3 as they don't command the same prices as the DD-2.<br />
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krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com9tag:blogger.com,1999:blog-942832708593410658.post-33585032592011009582017-08-14T19:13:00.001+01:002022-10-05T15:17:46.877+01:00Electro-Harmonix Pog (Big Box)<a href="https://dhttps://drive.google.com/file/d/0ByVCt2OFhXnyNURXckFJUTlJYmc/view?usp=sharing&resourcekey=0-DM-HZXCfQB50_p-1awD_cg">binary is here</a>Following the Nano POG & POG2, here is the original big box Electro-Harmonix POG. The big POG has mostly the same set of features as the POG2 - it doesn't have presets and the filter has fewer settings, but there are separate detune sliders for the 1 & 2 octave up harmonies.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUul5TpKMQnaWKG2LT-TsmY4L0TNFEcQgBkxBtM0EkBgIfUJImF9uZOdFZjW-vhBj98jx9UntFeQoSzWF4jYM3G9E24K2wP-raqRpm6wvfk2P3WaW_sHBBMfktrMgpM5TWIT_9J3QUXMD6/s1600/pog.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1266" data-original-width="1600" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUul5TpKMQnaWKG2LT-TsmY4L0TNFEcQgBkxBtM0EkBgIfUJImF9uZOdFZjW-vhBj98jx9UntFeQoSzWF4jYM3G9E24K2wP-raqRpm6wvfk2P3WaW_sHBBMfktrMgpM5TWIT_9J3QUXMD6/s400/pog.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">No slide pots were placed this time</td></tr>
</tbody></table>
In keeping with a trend I've noticed with EHX products, it's completely different on the inside than the other POG pedals. The <a href="http://falseelectronics.blogspot.com/2017/05/electro-harmonix-pog2.html">POG2</a> and <a href="http://falseelectronics.blogspot.com/2016/07/electro-harmonix-nano-pog.html">Nano POG</a> use Analog Devices BlackFin DSPs, the OG POG is much more late 90s and has a DSP56364 and a 8051-style P87C52 MCU, just like some<a href="http://falseelectronics.blogspot.com/2017/07/line-6-echo-park.html"> Line 6</a> <a href="http://falseelectronics.blogspot.com/2016/04/line-6-mm4-repair-and-dl4-conversion.html">products</a>, or the <a href="http://falseelectronics.blogspot.com/2016/08/digitech-whammy-4.html">Digitech Whammy</a>. I have no idea why this cheap microcontroller family is so commonly found alongside the DSP56K series but I'm starting to suspect there is an application note somewhere that shows how to use these parts together. The <a href="http://www.akm.com/akm/en/product/datasheet1/?partno=AK4552VT">AK4552</a> codec and 2272 & 5532 opamps are also very familiar by now. A <a href="http://www.ti.com/product/TLV1543">TLV1543</a> ADC reads out the slider positions.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8OSMdqgpvvlgOD2_ooABKItscpJhetmoEFApwLmcKnzbBlzeE8dR3dnRKuPKrrSbsRICwMsk1xvGSq1mL3L_oGTpBIBDBmPtuFjs3Ju6c_rDymsU9UH-JzO2ZjX5oXxWsS6P6Nl_ak-IK/s1600/guts.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1267" data-original-width="1600" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8OSMdqgpvvlgOD2_ooABKItscpJhetmoEFApwLmcKnzbBlzeE8dR3dnRKuPKrrSbsRICwMsk1xvGSq1mL3L_oGTpBIBDBmPtuFjs3Ju6c_rDymsU9UH-JzO2ZjX5oXxWsS6P6Nl_ak-IK/s400/guts.jpg" width="400" /> </a></div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-oUqb17darKJLiSPCL31Gku7fZNrOv8o4_tCt0QfZROpchcEDuMf6rgHgn-1mmOYSEYN0LDx6xwLeqG-19YmYvz5miTxcdBJvG4d5jz0KcvisWHjfFkxb-XzeGAg-xTdlNxI91rg2eY1n/s1600/IMG_1204.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-oUqb17darKJLiSPCL31Gku7fZNrOv8o4_tCt0QfZROpchcEDuMf6rgHgn-1mmOYSEYN0LDx6xwLeqG-19YmYvz5miTxcdBJvG4d5jz0KcvisWHjfFkxb-XzeGAg-xTdlNxI91rg2eY1n/s400/IMG_1204.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">DSP56364</td><td class="tr-caption" style="text-align: center;"></td><td class="tr-caption" style="text-align: center;"></td></tr>
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<br />
This pedal is also an outlier in that the complete factory schematic is online at <a href="http://www.freestompboxes.org/viewtopic.php?f=1&t=491">Freestompboxes</a>. The P87* series MCUs are OTP (but could be replaced with a compatible programmable part), so I have dumped this one. There is no other programmable part on the board so this should hold firmware for both the MCU and the DSP. The <a href="https://drive.google.com/open?id=0ByVCt2OFhXnyRlUyR3VHd2Z6em8">binary is here</a>.<br />
There are a lot of unpopulated parts in the PCB layout, some may be used for development and some look abandoned. There are footprints with silkscreen labels that indicate that they are for MIDI control and the schematic also indicates MIDI was planned at some point. I didn't experiment.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDYFyN9v-nH4ATefFA1cknqldb6I9yilbNHxhiSMiz1v7VzSp4iYYx9OBNWL5dRO-LkZUnHlBsik8EylkH6yvheLavRHxljrRKLtjy5ha89ccRs5DG9r3nF7OijJhnNpEwgFaTWB8nRLyM/s1600/IMG_1205.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDYFyN9v-nH4ATefFA1cknqldb6I9yilbNHxhiSMiz1v7VzSp4iYYx9OBNWL5dRO-LkZUnHlBsik8EylkH6yvheLavRHxljrRKLtjy5ha89ccRs5DG9r3nF7OijJhnNpEwgFaTWB8nRLyM/s320/IMG_1205.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Trashed slide switch</td></tr>
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No complicated fix for this one, once I had rigged up an 18V supply I found that the LPF mode switch was broken and a couple of wires looked like they were about to come off the board. After some solder touch ups everything worked fine. It sounds very much like the POG2, but as I don't own one anymore I couldn't do a direct comparison.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com3tag:blogger.com,1999:blog-942832708593410658.post-15584984363241109912017-07-15T18:16:00.001+01:002017-07-15T18:16:46.066+01:00Ibanez FL9A quick one. I got this original 80's 9-series flanger that didn't seem to be "flange-ing".<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjojm7jEWXGxYLLzXF42SDkPPoIbhR2God4YNkw7PcdRJ7YA7wkEMGeJVUexe-ASeer3RLh3SNyX0r1EeqBnvwA9llQCtqF_LPKeFRwjk3j0DR_IFlbR91l4M2TTs0al9sAi8myYqy1aoVA/s1600/fl9.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1034" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjojm7jEWXGxYLLzXF42SDkPPoIbhR2God4YNkw7PcdRJ7YA7wkEMGeJVUexe-ASeer3RLh3SNyX0r1EeqBnvwA9llQCtqF_LPKeFRwjk3j0DR_IFlbR91l4M2TTs0al9sAi8myYqy1aoVA/s400/fl9.jpg" width="257" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Ibanez Fl9</td></tr>
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When plugged in it gave out that tell-tale "whirr" sound when power was applied that some kind of delay was happening. It sounded like the signal was delayed correctly and mixed in with the clean signal, but nothing was happening with the LFO, so there was no "movement". First thing to check is if the Speed pot is wired up or broken.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizqYFOFoViK0E3uDmKRrOhiwRt-JtN4OyoAG7ynKg8KR5dAzxwdLlkPWHXE7bdrs0aDieYq7l775E8E8xpBs-ibut_TZjiOeJfrFMemqfDU0Aq-iZbG6DKpFqEAcpFNgmEDuASwJRRugyJ/s1600/IMG_1190.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizqYFOFoViK0E3uDmKRrOhiwRt-JtN4OyoAG7ynKg8KR5dAzxwdLlkPWHXE7bdrs0aDieYq7l775E8E8xpBs-ibut_TZjiOeJfrFMemqfDU0Aq-iZbG6DKpFqEAcpFNgmEDuASwJRRugyJ/s400/IMG_1190.JPG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Back of speed pot</td></tr>
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Hey, are those two lugs of the speed pot shorting together? I removed the pot and separated them with some needle nose pliers. The speed pot now varies the speed of the LFO and everything works as expected.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY-eE3LnuVEQ3KQWdBko87qmyLpi2jSpB67l19lQo8ODB_xmXJK7uxtqQfTry7fTeCgLgHgaWibYNedzU8BYUyo_-jNKEDmhR4nNb6Ka7jgezAEDZYZqbyjEFyuw9iHDcsJ7LXkeiKQ8zZ/s1600/pcb.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1600" data-original-width="1521" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY-eE3LnuVEQ3KQWdBko87qmyLpi2jSpB67l19lQo8ODB_xmXJK7uxtqQfTry7fTeCgLgHgaWibYNedzU8BYUyo_-jNKEDmhR4nNb6Ka7jgezAEDZYZqbyjEFyuw9iHDcsJ7LXkeiKQ8zZ/s320/pcb.jpg" width="304" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PCB topside</td></tr>
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A quick shot of the board while I have this open. The BBD and clock generator ICs are MN3207 and MN3102, manufactured by Mitsubishi. Build quality is pretty high for what was standard at the time. All the electrolytic capacitors are Nichicon brands, some have "8138" datecodes so I think this is 1981 vintage.<br />
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The flanger sounds great, but is much more subtle than the <a href="http://falseelectronics.blogspot.com/2017/06/mxr-evh-flanger.html">MXR I looked at </a>recently. This does chorus-style sounds much better rather than screaming airplane sounds. 9V operation is a bonus.krivxhttp://www.blogger.com/profile/09269425677953127430noreply@blogger.com3