Building the Gristlelizer pt 7: Enter the Multimeter!

Well, I’ve been putting off this entry because I was hoping I’d have better news, but it’s been a week so here’s the update.  The Gristlelizer is complete.  It turns on.  The LED glows, and when I adjust the Speed potentiometer, it speeds up and slows down.  Neat.  In “bypass” mode, I can clearly hear the signal source.

In Effects mode, nothing.  Nada.  Zilch.  Zip.  Zero.  The big empty.  Nothingness, not being.

I have never been so frustrated in my life.

All right, neither of those statemtents are quite true.  But I really am frustrated.  Here’s a rundown of the Gristlelizer’s current condition:

— Sound gets through fine in bypass mode
— When source is cranked and amp is cranked, you can JUST BARELY hear the source in effects mode. You can hear noise from the Gristleizer, though.
— The speed control is definitely doing something, as it makes the LED blink faster and makes the hum from the unit modulate accordingly.
— The shape switch similarly seems to be working.
— bias seems to be doing little if anything.
— level similarly seems to be doing nothing — EXCEPT that it will cut out the source sound if turned all the way in either direction.

I’d hoped for so much more!

I contacted Justin, who so impressively documented his Gristlelizer-building experience here:

Gristleizer Assembly and Test from Justin on Vimeo.

That’s pretty much what mine looks like — uh, except mine doesn’t work. I need to give major thanks to Justin who has been very generous in helping me try to troubleshoot what’s going wrong.  All the obvious things SEEM to be OK so far:  the capacitors and diodes and transistors are placed correctly, the solder joints are good.  Thus far I’ve also rewired all the pots and switches, and broken out the multimeter to begin testing all the components.  It just doesn’t WORK.


I am wondering if I may have fried the integrated circuits.  It’s only a couple of bucks to get sockets (which I should have used in the first place) and some new IC’s, so that’ll probably be next step in troubleshooting.  Wish me luck, and stay tuned.  If anyone else ran into any obstacles in the course of assembling their devices, please chime in — I’ll be quite grateful for any feedback or suggestions you can offer.


  1. Sorry to hear of the problems! If the LED responds to the speed control, then the bottom part of the schematic probably is working fine. So IC1, IC2, IC3, and IC6 should be okay. This means that the audio path above has the problem, but using a multimeter to diagnose an audio problem is pretty difficult!

    An idea would be to use the level pot as an audio probe.

    Temporarily remove the wire between pin 3 of the level potentiometer and the PCB and solder a long wire to pin 3 of the level pot. Use this wire to probe the circuit. For example, I’d think that probing IC4, pin 3 (the first integrated circuit that sees the input signal) would show that the signal is getting at least to the input of this first IC. Then start probing along the signal path, following the schematic, and listen for where the sound stops. (Keep the level pot at a middle setting until you know how loud each signal is.)

    IC4, pin 3 (input of the first IC in the audio path)

    IC4, pin 6 (output of first IC in audio path; should be louder than pin 3 because IC4 is wired for 11x voltage gain, or about 20 dB)

    SW1, pin 1 (also connected to TR2; with depth and bias turned down, should hear the signal)

    IC5, pin 2 (input of second IC in audio path)

    And finally, IC5, pin 6, output of IC5, the original connection for the potentiometer.

    I’m curious to hear what happens.

  2. Thanks for the suggestions, Kerry – will try this tonight. Replacing the IC’s didn’t help, but at least they’re all in sockets now, which I should have done in the first place.

  3. The ICs are bipolar, which is a bit more tolerant of static charge. Transistor TR2 probably is more static sensitive, being a FET. But since TR2 has only three terminals, it should be possible to determine if it’s working or not.

    My Gristleizer is nearly complete. Since it will be installed in a modular synthesizer, I made a special front panel. The potentiometers and most of the jacks have been wired. I probably will wire the switches tonight.

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