Digitech PDS 8000

I got this one for completeness sake after looking at the other PDS series.

The insides are very similar to the PDS 2000, with 4 times the memory. The PDS 8000 schematic is online, but the quality of the scan is so poor that the 2000 schematic is probably more useful.

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.

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.

Electro-Harmonix Micro Pog

I 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.

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 SS14, which is also the same part used for input polarity protection. The switching IC is a CS51413 buck regulator.

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.

 

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.

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.

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.

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.

 

That's it. Maybe someday I'll look at the HOG series as well.

Korg MS20 Mini

Korg MS-20 Mini Repair:

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.

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.

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.

There are 3 main PCBs, all mounted to the sheet metal case and connected together with cables.

1. Digital board - power entry and power supplies, the microcontroller, MIDI and USB ports.
2. Analog board - all synthesizer circuits, knobs, switches and jacks.
3. Keyboard PCB - breaks out the keys to a connector. I didn't look at this.

Digital Board (KLM-3163C):

The digital board is the largest difference between the Mini and the original MS-20, and unfortunately there is no available manual or schematic.

KLM-3163C

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.

I applied power and found that there was no voltage at the switch mode power supply inputs, and therefore nothing powering the analog board.

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.

Temporary fix to get things working

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.

I later confirmed the part number of F2 and replaced it.

Here are part numbers for all the ICs and transistors, from my notes:

F2 (?) - RRL025P03 - Pch -30V -2.5A Power MOSFET - used for power supply polarity protection. Amusing numerated "F2".
http://www.farnell.com/datasheets/2706699.pdf

IC1 - R1154H036B - 3.6V voltage regulator. MCU (IC3) runs at 3.6V.
https://www.mouser.com/datasheet/2/792/r1154-ea-923729.pdf

DT1 - DT4 - 2DTC114 digital transistors, marked "24" - used in other Korgs.
https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e
http://pdf1.alldatasheet.com/datasheet-pdf/view/201787/RICOH/R1154H036B.html

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.
https://www.rohm.com.tw/datasheet/BU4325G/bu42xxg-e
http://rohmfs.rohm.com/en/products/databook/datasheet/ic/power/voltage_detector/bu42xxg-e.pdf

IC3 - H8S/2210C - main microcontroller, covers keyboard scanning, USB & MIDI.
http://pdf.datasheetz.com/data/Integrated%20Circuits%20(ICs)/Microcontrollers/HD6473042F16-datasheetz.pdf

IC9 - JRC 4558 - opamp, not sure what this is doing.

IC44 - 74LVC1G126DCKRG4 - Single Bus Buffer Gate, marked CN5, also used in Kronos.
http://www.ti.com/lit/ds/symlink/sn74lvc1g126.pdf

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.
http://www.ti.com/lit/ds/symlink/tps54240.pdf

IC49 - TPS73801 1.0-A Low-Noise Fast-Transient-Response Low-Dropout Regulator - regulates the +14.5V rail.
http://www.ti.com/lit/ds/symlink/tps73801.pdf

IC50 - CD4011 - Quad 2 Input NAND gate
https://www.ti.com/lit/ds/symlink/cd4011b.pdf

IC 53 - TPS7A340 1–20-V, –200-mA,Low-Noise Negative Voltage Regulator - regulates the -14.5V rail.
http://www.ti.com/lit/ds/symlink/tps7a3401.pdf

DT1 - DT4 - 2DTC114 digital transistors, marked "24" - used in other Korgs.
https://www.rohm.com/datasheet/DTC114ECA/dtc114ecat116-e

PC1 - Toshiba TLP2368 Optoisolator - isolates the MIDI input.
https://www.kynix.com/Detail/697092/TLP285GB.html

Analog Board (KLM-3162C):

I also wanted to fix the headphone output, if possible.

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.
 

KLM-3162C with shield

KLM-3162C uncovered

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.

Headphone output circuit. C251 was removed for testing and later repopulated.

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 (?)

Offending 10 ohm resistors

Korg Service Manuals:

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:

MS20 Original service Manual
http://www.synfo.nl/servicemanuals/Korg/MS-20_SERVICE_MANUAL.pdf

MicroKorg Service Manual
https://elektrotanya.com/korg_microkorg_x-1110.pdf/download.html

MicroKorg XL Service Manual
http://dealers.korgusa.com/svcfiles/MKXL_SManual.pdf

Korg Kronos Service Manual
http://www.markpenny.ie/wp-content/uploads/2017/03/273600278-Korg-KRONOS-Service-Manual-v2-0-2012.pdf

Korg Volca Bass Service Manual:
http://www.ksadhu.niezba.org/sajty/korg_volca_bass_sm.pdf

Monotribe schematic:
https://www.korg.com/download/global/monotribe_schematic/monotribe_sch.pdf

Monotron delay schematic:
https://www.korg.com/download/global/monotron_delay_schematic/monotron_DELAY_sch.pdf

Digitech PDS 1700 Chorus/Flanger

I picked this up out of curiosity, I'm fond of the PDS series 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.

PDS 1700

There aren't too many surprises when comparing the insides to the PDS delays. There is the same ADC (ADC0820) 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.

Guts

PCB Backside

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.

PDS hardware. Input jack looks non-original.

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.

I replaced the switches, I'm using these. 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.

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.

I have this one listed on Reverb if anyone is interested.

Another Electro-Harmonix Freeze

I 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 I had seen before, 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.

Freeze Rev C PCB, flash ROM temporarily removed.

Main PCB, LM317 temporarily removed.

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.

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.

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.

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.

I found a great picture at freestompboxes (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).

U5 & U8 on another revision.

The Rev C board in front of me had "BA420" on both chips. Possibly EHX decided to run all 5V parts off of 3.3V, and doubled up on regulators? I don't know.an

To test this out, I decided to remove both chips and apply 5V and 3.3V from  external power supplies.

U5 & U8 removed, external power applied

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.

Current draw on 5V and 3.3V supplies.

I ordered L78L05ABUTR and MCP1804T-3302I/MB as replacement 5V and 3.3V SOT-89 regulators. I also used 2MD3T2B2M2RE 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.

Ibanez DDL10 Delay II

This 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.

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.

DDL10 internals

The bottom PCB has two 4164 DRAMs, an NE571 compoundor, LM311 comparator (most likely used as part of an ADC as in the DD-2 and PDS delays) 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.

Main PCB, component side

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).

Main PCB, back-side.

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.

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.

DFL10 schematic page 1.

DFL10 schematic page 2.

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.

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.

Faulty capacitor pulled.

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.

Red Panda Particle

It's been a while. I have been doing repair jobs and not posting them, so I will try to clear the backlog.

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.

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.

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.

Interior layout.

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.

IC10 removed.

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.

I did dump the EEPROM. Looking at it briefly with the excellent online FV-1 decompiler, 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.

Voodoo 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.

Main PCB

No surprises on the insides - there is an P87LPC764 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.

Hacked in parts at the power input.

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.

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.

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.

Replaced MAX1044 (pictured here sitting crooked in a socket) and lifted diode D10

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.

TC Electronics Nova Drive NDR-1

Programmable 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.

 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.
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.
This series used a 12V power supply for some reason (why not 9V, like everything else?)
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.

Top PCB (digital)

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.

Lower PCB (analog)

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 Cirrus CS3308. 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.

Lower PCB, backside

U3 generates -12V from 12V input

All parts on this side are glued in placed before soldering

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 CS51411 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.

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.

There is another switching power supply using a L5970D controller - this one is generating 3.3V for the digital parts and was working correctly.

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.

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.

The CS51411's inductor measured 33uH out of circuit which seemed correct. I decided to try swapping it with this part, 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.

All good again.

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.

Electro-Harmonix Pitchfork

I don't know if the PitchFork exists alongside the POG series 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.

The insides are very similar to the newer POG pedals, with an Analog Device Blackfin DSP (ADSP-BF592) and a AKM AK4552 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.

Picture taken after repair - clean.

Taken before repair - PCB appears cloudy

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.

11-detent "Mode" pot showing some stains

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.

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.

Original DC jack

..and underneath the jack

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.

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.