Tonebender MK2 voltages

Started by soundkarte, March 26, 2009, 01:01:16 PM

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soundkarte

I have been working on a TB MK2 on my breadboard, and have a question about the voltages I'm reading on Q1 / 2 / 3.
Built the stock PNP layout from Fuzz Central, with 2 changes;

47K on Q2 collector
20K trimpot on Q3 collector

Q1-3 are PNP russian trannies, hfe = 66/66/112, all below 300 leakage as measured by R.G's method.

8.8v battery at test:

Q1 - C= 8.66 / B= 35.6mV / E= 0
Q2 - C=.649 / B= .121 / E= 0
Q3 - C= 4.56 / B= .645 / E= .523

From other posts, the numbers seem "close", except for base at Q1 which is less than half or worse!
I've tried upping the resistor to ground of Q1 base, but cannot get above 45mV.

The build sounds good, but I'm curious.
Any thoughts or other info I should provide?
Thanks!




B Tremblay

If it sounds good, then it is good.

Those voltages are in line with ones seen here:
http://home-wrecker.com/tbmk2.html
B Tremblay
runoffgroove.com

soundkarte

Thanks!
Any ideas on the Q1 base being so low?
I tried the supa-fuzz mod with the bigger caps and 10K to ground on Q1 base, and got 6mV (?)

petemoore

Any ideas on the Q1 base being so low?
  It is connected to ground.
  The collector...seems like it should maybe be closer to 1/2v...
  The 1rst transistor is a boost stage, audio probe tells more what it's doing as far as boosting/distorting, the collector has a very short swing to supply rail from it's present bias point.
Convention creates following, following creates convention.