I can't get my fuzz pedal to work - Any suggestions?

[marty.c]

Hi,

It's my first time building a stompbox and so I figured I would go with a fuzz pedal because it seemed to be the simplest way to go. I don't have a lot of experience with electronics, but the schematics I found looked pretty straight forward.
It's the standard fuzzface setup, with npn transistors and negative to ground. I'm using 2n3904's for Q1 and Q2. I've set everything up on a breadboard and I get no signal at all when I plug it all in.

I've checked each component and connection, replaced transistors and caps for good measure, and still nothing. The strange thing is that when I remove the ground connection from the 1K fuzz pot, it seems to work. I get a signal and it's got a pretty consistent and solid distortion. It's pretty rough, but it carries a tone. Clearly this is not correct, but I've spent 2 days building and rebuilding this circuit and I'm getting the same results each time. I've tested the pots, caps, and resitors, and all looks fine (as far as I can tell). If anyone here can point me in the right direction that would be awesome.

I've tested the voltage on the transistor pins, and the results are as follows:

Q1 - 2n3904

e- ground
b- 0.26
c- 0.96

Q2 - 2n3904

e- 0.28
b- 0.96
c- 0.31

This is the schematic I used, the only thing I've changed is for C2 I'm using a 22uf instead of a 20uf.
http://www.muzique.com/schem/fuzzface3.gif

[diydave]

Rour voltages of q2 are way off. q2 is not conducting, probably due to misbias.

Replace r1 of r3 with a trimpot. This way you can dial into the correct bias. That is 4,5 volts at the collector of Q2.
Or tune by ear.

Hope it helps

[marty.c]

Thanks diydave, you got me looking into my resistors again, and it hit me like a slap in the face, I've used a 330k for R2 when it should have been 330 ohms. I was only wrong by a factor of one thousand! No wonder it didn't work. I'd say rookie mistake but that's probably insulting to the rookies. Good call on the trimpots though, that seems like a good thing to do regardless.

[petemoore]

I've used a 330k for R2 when it should have been 330 ohms.
  Oh good !
  I used to make the same math but with 470 / 470k...more than once !

[smallbearelec]

2N3904 x 2 may sound harsh. Since you are already on the breadboard, there are some suggestions in here that you might want to try:

http://www.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

Regards
Steve Daniels

[marty.c]

The 2N3904's were the only ones I could pick up locally, but now that I've got the thing working I'll definately look into improvements and send away for better gear. Thanks for the tips, man this stuff is addictive!

[diydave]

Wait until you get to know about tube's and amps. 
Lots of luck with future builds.