Musikding Fuzz Factory: Drive pot doesn't effect the sound

[Asbetosdeath]

Hi guys!

I recently assembled this nice pedal. It does sound, and has some great tones (provided with whistles and self-oscillation as the original); the only issue is the Drive pot, which is not affecting the sound in any way.

I'm quite sure everything else is working fine; as for the pot itself, it's working.

Q3 probably hates me since i cut its legs way too short, but in the end i managed to solder it anyway... i looked at the schematics, and i'd say it is not to blame (the COMP knob is working properly, too).

I didn't check tension values yet, but I'll do it if somebody is willing to help me with that.

Any clues?

Thanks!

Edit: Musikding Fuzz Factory schematics

[52 Bill]

I'm not familiar with that circuit, but it looks like a buffered fuzz face, made to run off a positive 9 volt supply.

The drive control is wired in parallel to the comp control. When the comp control is set for minimum resistance it basically shorts the drive control out. Try setting the comp control to maximum resistance and then sweep the drive control and see if it changes the gain of the circuit.

[Asbetosdeath]

Thanks for the reply! Of course i tried the drive pot along with every possible settings of the others, and it's not doing anything at all (unless i'm missing something happening in the ultrasonic range). Comp is working fine
I'm pretty clueless here, since I'm sure the solderings on the pots are fine (I double-checked)...

Those 2 knobs (comp and drive) are basically biasing Q2 base and Q3 emitter, aren't they? But what is C3 doing there?

I guess I have to check Q2 and Q3 voltage reading now!

[52 Bill]

Those 2 knobs (comp and drive) are basically biasing Q2 base and Q3 emitter, aren't they? But what is C3 doing there?

Normally C3 would act as an emitter bypass cap increasing the gain of the second stage, but as I tried to point out earlier if the comp control is set to zero ohms, the cap and the drive control are paralleled with it and can't have any effect on the stage gain.

[Asbetosdeath]

Normally C3 would act as an emitter bypass cap increasing the gain of the second stage, but as I tried to point out earlier if the comp control is set to zero ohms, the cap and the drive control are paralleled with it and can't have any effect on the stage gain.

I see, but it's not the case, since the "drive" control is not influencing the sound regardless of "comp" settings.

I did some reading; Q2 doesn't seem to be affected much by "drive": surprisingly (for me, at least), only the tension on its Collector varies, from 4.30 to about 4.8v (every other knob turned full counterclockwise).

As for Q3, here are the values: (other pots at 0, "drive" going from 0% to 100%)
E 4.38 to 4.50
B 4.32 to 4.77
C 1.04 to 0.62

I fell more confused than before, if possible :/


EDIT: once closed the box, after the readings, I gave it another try. The pot IS NOW WORKING for the first time... O___O This is crazy...