Debugging the Green Big Muff.

[nascarbean_97]

I used the Sovtek Green Big Muff vero layout from Tagboard Effects, and it's verified.



I followed the layout exactly, and I did drill the vero, thanks for asking.  

As far as parts substitutions go, I used 2n5089s for the trannies, and non-polar 1uf caps instead of polarized ones. I also wired a 4n7 cap from sw1 to tone 3 instead of a switch.

It's working as a clean boost with the tone stack fully functioning, the sustain knob does nothing whatsoever.

Transistor Voltages:
Q1:
C: 39mv
B: 1.7v
E: 1.1v

Q2:
C: 0.656v
B: 0.656v
E: 53mv

Q3:
C: 3.7v
B: 0.622v
E: 33mv

Q4:
C: 3.8v
B: 0.69v
E: 31mv

Power at the source: 9.14v

[Pyr0]

The sustain knob wont do anything with those transistor voltages, it sits between Q1 and Q2, and the collector voltages on q1, q2 are not right, the transistors are not doing anything.
for starters, it looks like q2 has its collector shorted to its base, both have the same voltage, so check for solder bridges around it.
The collector of q1 looks like it is also shorted to something else, normally on any big muff, the collector voltages should be around 4.5v.
Check for minutes solder bridges between tracks around q1, and also check that each track cut is actually cut, sometimes there can be a hairline piece of copper joining the track if not cut properlly, if need be buzz them out with a meter.

[nascarbean_97]

I went between the vero tracks of Q1 and Q2's collector and base, and now it works like a charm! Thanks for that help!

[LucifersTrip]

ironically, I just measured collector voltages on my killer sounding original



I just breadboarded a Triangle and it too has ~ 5.5V on Q4 collector, which sounds warmer than at 4.5V
The higher gain the transistor, the lower the collector voltage.

[Pyr0]

I've been following your other thread on triangle voltages, so do you reckon it's worth putting in some lower gain transistors for Q4 ? I've hundreds of various new and NOS transistors with gains from 40 up to the high hundreds. And I'm just finishing a Russian Civil War muff, maybe I'll play around with a few lower gain transistors in it.
Oh and where did you get those cool red capacitors ?

[nascarbean_97]

Those flat caps, do want. Those russians.   

[LucifersTrip]

I've been following your other thread on triangle voltages, so do you reckon it's worth putting in some lower gain transistors for Q4 ?

man, it's all personal taste...definitely try it, though. I found it definitely warmer. I did one more "middle" hfe experiment. I pulled all four 80 hfe-ers and subbed in four with hfe's ~ 225. It dropped all collectors to the 4.6 - 5v range and sounded like crap...totally thin and trebly. I was a bit surprised at the big difference...

Oh and where did you get those cool red capacitors ?

that's an original !