My Fuzzface requires a signal stronger than my guitar...

[joakim]

"Ground" in your case the the +9V because you've got a slightly unorthodox layout. If you connected the base it to 0V, you let all the current that could run through the base-emitter junction, basically a short circuit which is why it got hot  

As you've now got things socketed, you can now easily swap the transistors around and ti see if just one is acting funny. You can also try putting in a silicon pnp diodes to see if there is something wrong with your layout.

Tomorrow I'll try connecting Q1b to VCC, then, and report back :-)

[dwmorrin]

  Sorry about the short!  I must have forgot about your "negative ground" schematic.
Safer instruction would have been "short base to emitter."
My apologies if I cost you a transistor.

Looks like you got some movement on Q2's collector.  I have a strong feeling that your circuit will work with some tailoring of the resistor values.

[joakim]

OK, so with Q1b shorted to Q1e = VCC = 8.64V, I measure the following voltages:

(with R1 = 33k)

Q₁:
V_C = 1.22V
V_B = 0
V_E = 0

Q₂:
V_C = 1.10V
V_B = 1.22V
V_E = 1.09V



(with R1 = 15k)

Q₁:
V_C = 1.47V
V_B = 0
V_E = 0

Q₂:
V_C = 1.33V
V_B = 1.47V
V_E = 1.32V

... so, V_BE does look like a Ge diode drop (~0.15V), right? 

[joakim]

 

I decided to test the effect pedal (in its box) again, with the 15k R1 resistor, what with all the regained confidence from you guys... and it seems to work!
Not sure if it's got the right Fuzz Face Sound, but hey I'm VERY happy just that SOMETHING happens when I click in the effect!

One problem still has to be fixed, though: there's a rather nasty hum when the effect is switched in. There is no hum during clean sound (effect bypass), so the hum has to originate from the effect circuit somehow. I would dare say that the fact that there's no hum on the clean sound (where the input is directly connected to the output, physically bypassing the circuit using the "Millennium True Bypass") would rule out grounding issues, or that something is shorted to the metal box (I've also checked this with the multimeter). Still, if I touch the box and metal on the guitar (strings, nut, or even the sleeve on the guitar cable jack) the hum stops...

My obsevations lead to these humble "conclusions": there is an obvious risk in having electronics inside a metal box, and since the hum stops when I touch the casing + GND, should I perhaps simply go ahead and connect the sleeve pin of the input jack (or some other GND point) to the case? Or is this a symptom of something wrong with the circuit?

During debugging, I was looking for the proper "FXOUT" point on the PCB to connect the audio probe. Comparing my Eagle circuit to the original Fuzz Face schematic, I was suddenly unsure whether I've connected the "output decoupling capacitor", C2, correctly. As I understand, its purpose is to ensure no DC can leave the effect circuit and travel to the amp/speakers. This looks very convincing on the original schematic, but did I get that right on my schematic?

[PRR]

The box must be connected to the guitar ground, typically through the cable-plug shell and jack body.

After 4 pages I can't remember what this build looks like but it should be easy for you to check.

[joakim]

Big thanks to everyone here for helping me out! Can't believe I actually finished this project, after all this time!
It'll be fun to hand this back to my friend