"5 knob fuzz" oscillating all the time

[Bonehead1996]

So I built a 5 knob oscillating fuzz clone many years ago that was an absolute monstrosity (vero board, awful soldering etc.). But recently I decided I should re-make it and bought a PCB for it. I soldered all the components in (using mainly the same ones from the original vero one) and wired it all up and now it oscillates in the background constantly. I can dial in huge oscillation with the stab knob but when I set it to what should be a cleaner setting theres still a loud oscillation in the background that makes up about 25% of the signal.  Does anyone know what it could be? The transistors aren't the issue (I've tested 10 others) and the knobs dont affect the background oscillation. Using an Audio probe on the circuit I can't find any hint of oscillation until the output of Q3.

[vigilante397]

Welcome are you referring to the fuzz factory then? Stab will help tame the oscillation a bit, but all the controls are pretty interactive so the gate is a huge part of quieting it down. Hope this helps! 

[GibsonGM]

Hi Bonehead, welcome.   Read this thread:  http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

There are 1,000,000 reasons a circuit will oscillate.  Most likely, you are running signal wires to/from other circuit areas across a high-gain amplifier (transistor).  This causes a feedback loop, where already-amplifed signal is re-amplified, and makes that howling/whining.   There are many threads on this subject, try searching      Moving the wires around, decoupling, using shielded wire are some ways to stop this problem.

post a schematic if you can, too....there could be an error around Q3 (or elsewhere), wrong value component, etc., but hard to say with the debugging info...

[Bonehead1996]

Welcome are you referring to the fuzz factory then? Stab will help tame the oscillation a bit, but all the controls are pretty interactive so the gate is a huge part of quieting it down. Hope this helps! 

Thanks I am indeed, wasn't sure what the rules were on naming them . I've used a fuzz factory for several years and understand controlling the normal oscillation but this is a background oscillation that doesn't respond to the controls and doesn't decrease when you adjust anything, just the gate control removes enough low level noise to remove it. I think it's probably gonna be an issue with cabling or something :/. The PCB I'm using is one bought from fuzzdog/ pedalparts and I've triple checked my component values :/. Thanks anyway

[vigilante397]

Okay, that's a pretty good place for us to start. Can you post pictures of your build and check voltages on the transistors? That woukd make it a lot easier for us to help pinpoint the problem