Debugging Fuzz Face

[Kearns892]

Alright, I'm on my second build and I've run into a snag building a fuzz face.

1. I am using the Fuzz Face schematic from Beavis Audio.
2. http://www.beavisaudio.com/bboard/projects/bbp_FuzzFace_Rev1_1.pdf
3. Right now the circuit is in the breadboard stage, this is just circuit no LED, or switch.
4. The only change I made to the schematic is I substituted R4 (originally 8.2k) for an 8.8k Resistor.
5. I'm running this circuit just like the schematic with NPN transistors.
6. I get no signal, but I'm running this through an amp that has some buzz problems of its own, and from this I can tell that the volume knob does work.
7.
Q1
E=8.71 V
B=7.92 V
C=8.92 V

Q2
E=8.70 V
B=8.92 V
C=9.15 V

[yeeshkul]

Q1B is way to high, start there. It should be around 0.6V - the DC on Q1 base is provided just by the 100k feetback res.
Measure the way the pins on your breadboard are connected together.

After you have found the bug use 25k trimpot instead of R4 so you can play with Q2C.

[Kearns892]

Thanks, I'll try that in the morning, it's too difficult to debug without a clear mind.

[Kearns892]

And I don't have any trimmers on hand, for prototyping purposes would a 20kB pot be fine?

[yeeshkul]

absolutely

[Kearns892]

Alright, I went back over checked my connections and values and it all checks out. I lose some voltage over the 100k resistor but just about 1V. What exactly should I be looking for, or is there anything else that could be causing this?

[Kearns892]

Should Q2 be emitting over 8 volts? All the energy going to Q1B is comming from the emitter which goes through a 100k resistor which knocks us down about 1 volt. Should the resistor be resisting more or should the mitter be emitting less?

[slacker]

There's something seriously wrong somewhere. The emitter of Q1 is connected to ground so you have to have 0 volts there.
Are you using a stereo jack to switch the battery on and off? If you are you need to have something plugged into it when taking voltages otherwise you get weird results like you're getting.

Another thing that might be wrong is that if you've laid it out like shown in the Pdf you need to connect the 2 negative columns together otherwise everything isn't grounded correctly. What I mean is that the column that the jumper from j14 connects to needs to be connected to the column that the jumper from a10 connects to.

[yeeshkul]

The thing is not grounded, the ground strip is usually connected horizontally  where the rest is connected vertically. Check out how the breadboard pins are connected.

[Kearns892]

There's something seriously wrong somewhere. The emitter of Q1 is connected to ground so you have to have 0 volts there.
Are you using a stereo jack to switch the battery on and off? If you are you need to have something plugged into it when taking voltages otherwise you get weird results like you're getting.

I am not using stereo jacks, right now to eliminate outside possbilities i have the bare circuit going here. Q1E is only connected to a jump going to ground, if that should be 0 could this mean a bad transistor? It's brand new.

Another thing that might be wrong is that if you've laid it out like shown in the Pdf you need to connect the 2 negative columns together otherwise everything isn't grounded correctly. What I mean is that the column that the jumper from j14 connects to needs to be connected to the column that the jumper from a10 connects to.

What I have actually done is jump the ground at a10 all the way over to the other side of the board and i have the left column of the left bus as power and the left column of the left bus as ground.

I built this circuit originally from the schematic, had the same problem I'm having now so rebuilt just like the breadboard layout the only way i have diverged from the layout is by having a single jumper wire  instead of two at row 25 and 16 which shouldnt matter

[Kearns892]

Aha! I had the ground wired correctly but this bread board has some issues, when I moved the ground to a different pin in the same row I got .57. Now to test it

[slacker]

Cool that sounds better. I was going to ask if it was the same dodgy breadboard you'd already posted about, sounds like it's time for a new one

[Kearns892]

That helped, now the knobs do stuff, just not the right stuff, I'm picking up radio and they're talking about gay marriage the volume knob changes the clarity, is this just because im on a bread board?

[Kearns892]

Ok, I got it working i just connected all the grounds directly to the ground of the battery snap with a stripped wire and a ton of alligator clips, its unbiased but works. Next project, find all the holes in this board and mark em off.

[yeeshkul]

The breadboard is not shielded = random radio receiver (where R-C parts work like a demodulator, the bare wires become the arial)