General Guitar Gadgets Fuzz Face Gate/No Sound Issue (GGG Dual FF/Rat build)

[nicholasvbest]

Hey y'all. Bought a GGG dual pedal kit and got half of it to work perfectly, would really love some insight bc I don't know what to do! Almost no sound comes out until I strum real hard- its incredibly gated, or something. More info below

It's two Effects in one box, single DC Jack, each pedal with True Bypass/LED indicators, inputs grounded. Here's a wiring diagram for the dual kit

First pedal in the chain: Silicon Fuzz Face, smaller PCB (most basic version, negative ground, NPN 2N3904 silicon transistors)
Fuzz Face instructions
Fuzz Face circuit diagram
Fuzz Face wiring diagram

Second pedal in the chain: Rat, bigger PCB (negative ground)
Nothing special here, works perfectly.


Back to the fuzz face- The instructions offer some optional mods, I added them all (e.g. optional trimmer in R5, what I assume is a bias knob? R1 switching "pop" eliminator, C4 RF interference eliminator, C6 power filter, D3 reverse voltage protection)

Changes/repairs made:
I removed C4 thinking it was physically broken, doesn't matter for now. I also broke a transistor and replaced it with a new one of the same model number. After trying the pedal a few times, I removed a stray wire that was shorting F3 to L, and another stray wire that was shorting the bottom right switch lug to the middle right switch lug (Including in case of any weird incidents that could've happened while I ran the pedal with the shorts...)

Restating as per debugging instructions that the FF uses NPN transistors on a negative ground pedal

The issue: the Fuzz Face sounds fuzzy, but only if I hit the strings hard enough. Until then, there's no sound from the FF side, like some crazy gate or something. Messing with the trimmer gives different "gate level" results, none of them usable. I'm told this is a transistor issue? What could be making my Q2 collector voltage so high? Fuzz Face voltages below. Once again, the Rat works perfectly, sounds great, which makes me think my problem is isolated to the FF.


Disengaged pedal:
Test battery measures 8.99V

Tested Q1:
c: 1.18
b: 0.6
e: 0

Suggested  Q1 (from GGG):
c: 1.4
b: 0.6
e: 0

Tested Q2:
c: 8.68 (sweep max range .10V)
b: 1.18
e: 0.71

Suggested Q2:
c: 4.5 (adjusted w/ trimmer)
b: 1.4
e: 0.8

D3:
a= 0
k= 8.73

What gives? Any help is appreciated. I'll try and get a better pic up within the next couple of weeks...

[willienillie]

What you describe sounds like a bias issue.  How low can you get your Q2 collector voltage using the trim pot?

[nicholasvbest]

What you describe sounds like a bias issue.  How low can you get your Q2 collector voltage using the trim pot?

I left the battery and a input cable in, 9V died a bit, whoops...

At 8.66V from the battery with pedal engaged, Q2 collector sweeps from 8.03 to 8.13ish. Pedal disengaged, sweeps from 8.34 to 8.44. Should've included the sweep in the post!

[willienillie]

Not much sweep.  What value trimmer did you use?  Is there a fixed resistor in series with the trimmer?

[nicholasvbest]

Not much sweep.  What value trimmer did you use?  Is there a fixed resistor in series with the trimmer?

10k trimmer, 1k fixed resistor in series, pretty sure it's after the trimmer? Not sure if the order* matters, wiring diagram linked

[willienillie]

No, the order doesn't matter.  Is there any chance you installed a 1K trimmer instead of 10K?

[nicholasvbest]

No, the order doesn't matter.  Is there any chance you installed a 1K trimmer instead of 10K?

Def 10k, just verified