Eurotec Black Box Faze Module

Eurotec 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.

Image from https://www.tonehome.de/eurotec/

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.

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.

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.

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.

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.

Adding external power:

Despite having an LED, there is no indication that the pedal is active when pushing the footswitch.

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.

Full modular system - image from https://www.tonehome.de/eurotec/

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.

This seems like a worthwhile cable if you don't want to modify the enclosure.