GT311 Face Bender debug

[ibodog]

Anyone see anything wrong with this schematic or layout?  I always get around 8V on the collector of Q1 no matter what value resistor I put in for R2 (values from 2.2K to 100K!).  And there is a horrible crackling sound when I move my guitar volume knob when in "face" mode.  I adjusted R6 to 1K and was able to adjust to ~4V.  The "face" side sounds pretty good except for the crackling from the volume knob.  I didn't implement the LED switching stuff at the bottom of the schematic.  You know, I would have sworn I got this schematic somewhere here, but I can no longer find it. BTW I've got GT311A's.  Pinout for these is correct as shown on the vero.

[anchovie]

I've got some of those transistors - the first Tonebender that I built with them was a hybrid that used a silicon for Q1 but I recently built an all-germanium version. The internal shunt resistor in the tranny makes it behave slightly differently so it didn't work first time and Q1 was the problem, but adding a resistor from 9V to the base of Q1 solved this because it forms a divider with R1 to bias the input away from ground.

I used a 10K on the collector of Q1, a 47K for Q2 and a 10K trimpot for Q3, though I may have been lucky in this case to get away with a low value trim.

[petemoore]

  Q2 of Fuzzface = Q3 of Tonebender.
  Tonebender is a fuzzface with another transistor preboost.
  I never had to go below around 6k8 for the Fuzzface Q2 collector resistor, anything over about 18k...instead of going outside this range, I'd start looking for transistors that biased with a 10k trimpot+6k8 stop resistor, it provides a range of 6k8 - 16k8 adjustment, and the 10k is nice because fine-tuning is easy. 

[ibodog]

I've got some of those transistors - the first Tonebender that I built with them was a hybrid that used a silicon for Q1 but I recently built an all-germanium version. The internal shunt resistor in the tranny makes it behave slightly differently so it didn't work first time and Q1 was the problem, but adding a resistor from 9V to the base of Q1 solved this because it forms a divider with R1 to bias the input away from ground.

I used a 10K on the collector of Q1, a 47K for Q2 and a 10K trimpot for Q3, though I may have been lucky in this case to get away with a low value trim.

Yeah, adding a resistor from 9V to the base of Q1 didn't work in this scheme.  It did drop the voltage, but way down into the 50-100mA range.  I tried 100k, 10k, 1k, 470R. 

Does the schematic look OK?

[anchovie]

My apologies, I forgot to mention what resistor I used! I've got a 470K from 9V to Q1 base and the same 100K that the schem shows from base to ground. I didn't use the 47pf cap and I used a 100nF off the Q1 collector. Aside from that, my first stage is the same as in that schem.