Debugging a fuzz face clone help?

[samuwel]

So I built a fuzz face. Bypass works, but no sound when fuzz is switched on.

I used this layout : http://smallbox.zeonhost.com/projects/fface/ as it's my first build and lays it out nicely for me to see 

I heard bad things about using a negative ground in a fuzz face (oscillations) so changed the circuit back to the original schematic as per here: http://www.muzique.com/lab/fuzzface.htm

It still doesn't work. any clues why?

I'm using 2 AC128's

Battery: 8.88V

Q1:
E 0V
B 0.08V
C 0.30V

Q2:
E 0.13V
B 0.40V
C 8.76V

Thanks in advance

[station]

http://www.generalguitargadgets.com/pdf/ggg_ff5_instruct.pdf

[Spidermonkey]

Any pictures of your board? I just built a silicon fuzz face, so it could be somewhat different, but I had the exact same voltages as you for the transistors, with Q2C much too high. Turns out I had accidentally connected my lug 3 of Fuzz to Q2B instead of Q2C. Could this be your problem?

[TheNixon]

Try to isolate the problem. Turn the effect on and connect input and take ouput wire and start testing on different points in layout if signal passes. Start with input then continue with transistor. Check if signal comes in transistor and if comes out. This is the simplest method if you don't have an oscillocope. I solved many problems that way. Many times the only problem was the different transistor pinout.

[samuwel]

Any pictures of your board? I just built a silicon fuzz face, so it could be somewhat different, but I had the exact same voltages as you for the transistors, with Q2C much too high. Turns out I had accidentally connected my lug 3 of Fuzz to Q2B instead of Q2C. Could this be your problem?

I'm pretty certain that isn't the problem , The board is really spaced out and laid out in a way so that I think I sort of know what's going on with it.

Pics of the board:






any clues?

[Spidermonkey]

Check the orientation on Q1. It looks like the emitter is going north, towards the 33K resistor on your board, rather than South towards the 100k one, but its kind of hard to tell. What value is your little blue capacitor, i doubt thats the problem, but it's interesting that you could get one that small (might be helpful on some tighter builds!).

[samuwel]

Q1 is the right way, it just twisted slightly when i was trying the circuit for size in a guitar.

The blue cap is an 0.1uf. It's pretty small yup.

Having messed about with an audio probe as suggested for a while, i'm a little closer to working out what's wrong i think? should be sound at the collector of Q2?

[Spidermonkey]

Hm. If you are getting sound at Q2C, your problem could be either the 8K2 resistor or the 0.1uf cap. Your output goes into lug 3 of the volume pot, and out of lug 2 to the switch to the jack. So if there is sound at Q2C, the only things between that and output are the blue cap, the 8K2 resistor, volume pot, and the switch. If that's not it, I'm lost. Hopefully that's the problem!

[samuwel]

there is no sound at Q2C 

[Spidermonkey]

Im not sure what to do then. I know your Q2 voltages are much different then what they should be. I just built a fuzz face clone, and i have a battery with the same charge as yours, so I'll post some tranny voltages for you to compare. Something isn't pulling down Q2C's voltage as it needs to. Here are my voltages-
Q1
E- 0
B- 0.58
C- 1.24

Q2
E- 0.64
B- 1.24
C- 3.39

Double check your wiring too. Your voltages are eerily similar to mine when it didn't work.

Hopefully you can figure something out.

[samuwel]

Cheers for the help anyway.

Anyone else have any ideas?

[jdub]

Offboard wiring OK? Can't tell from pics...

Also, any chance of a clearer shot of the solder side of board? 

[samuwel]

I've checked for continuity on my offboard wiring and double checked that everything goes to the right places, seems okay to me.

Should I get continuity between Q2C or Q2E and ground? I don't with either of them...

[Quackzed]

i'd check your resistor values with a dmm... are the 2 horizontal resistors 1k at the top and 100k at the bottom?I still have a hard time reading those resistors with more than 4 bands...

[samuwel]

urgh I've just checked my resistor values and a couple of them have changed since I put them in (yes I measured them then)

I'm gonna have to get some more on monday when I'm at uni. Yay for being an engineering student.

[Quackzed]

they may read differently in the circuit just due to other paths of continuity in the circuit , as long as the color codes are correct for the values you want you're probably ok. otherwise the circuit looks pretty good to me... hmmm.
wait, are ac128's positive ground? as in pnp? or are they npn transistors? i think they are pnp, so you hook the battery up with + to ground and - to +9v (switch the battery terminal connections on the board) and reverse the orientation of any polarized caps? i think but i wouldn't want you to fry anything because i'm wrong...
as long as the schem you used was for pnp transistors you're cool. and don't need to reverse anything...

[oliphaunt]

128s are PNP.

[samuwel]

Okay, so I'm gonna take the resistors out and remeasure when I get the chance anyway....

with regards to the PNP/NPN, yes they are PNP. I built the circuit both of the ways on this page :http://www.muzique.com/lab/fuzzface.htm (negative ground first, but then changed to positive ground in case the negative ground was causing a problem)

Can anyone help me Identify specifically where the problem may be?

[head_spaz]

[jdub]

Checked for cold solder joints?  Looking at the picture of the solder side, the joint on the left side of the yellow wire (appears to go to emitter of Q1) looks suspects.  Also, any chance that you fried the transistors?