Troubleshooting a DBA Fuzz War Clone

[Xplorervoodoo]

Hey guys, I built Johnk's 7 transistor 2 knob Fuzz war, (found here: http://guitar-fx-layouts.42897.x6.nabble.com/file/n7138/DBAFuzzWarV2-01.png) and I'm having problems with it.

Before I start, I'll say that I changed the 20n cap to a 22n because I don't have any 20s.  Also, the 680p cap is a 560p in mine, I think.  Also, I changed the 2n5089s to 2n3904's due to the explanation in the thread that the 2n5089s are problematic.

Basically, here's the short version of what happened so far.

I built the board, wired it up, and when I tested it, the LED came on, but I barely got any sound out.  Seems like there were spikes.  I put it on my test box to eliminate the offboard wiring, and it worked perfectly.  Then I came to find out that the test box was only supplying about 1.3 volts.  I corrected that to about 9.5 volts, and the pedal stopped working again.

I took some transistor measurements, and here's what I found:

Input voltage 1.6V:
Q1 - e - 1.507
b - 0.550
c - 0.087

Q2 - e - 0.019
b - 0.550
c - 0.005

Q3 - e - 0.612
b - 0.533
c - 0.005

Q4 - e - 0.063
b - 0.532
c - 0.004

Q5 - e - 0.064
b - 0.532
c - 0.004

Q6 - e - 0.594
b - 0.511
c - 0.003

Q7 - e - 0.742
b - 0.509
c - 0.002

Input voltage 9.26V:
Q1 - e - 8.89
b - 0.642
c - 0.173

Q2 - e - 0.043
b - 0.642
c - 0.036

Q3 - e - 0.391
b - 0.627
c - 0.043

Q4 - e - 0.050
b - 0.611
c - 0.028

Q5 - e - 0.050
b - 0.611
c - 0.028

Q6 - e - 0.664
b - 0.584
c - 0.022

Q7 - e - 1.509
b - 0.580
c - 0.021

Any ideas as to where I'm going wrong?  I find it strange that the circuit works perfectly at 1.6V, but not at all at the full 9V...

[duck_arse]

Xp, can you find us a circuit diagram, please?

"The later 3-knob version has 7 transistors and is notoriously difficult to get working." I won't tell you where I found that.

[Xplorervoodoo]

I'm not too clear on which circuit was used, tbh.  From what I can gather from the thread, someone had posted pictures of their Fuzz War's PCB, and a vero was constructed from that.  There were 3 different 7 transistor versions, and all were supposed to be verified, from what I understand.  The version I built was the only 2 knob version, since I just wanted the simplest Fuzz War, in terms of controls.

http://guitar-fx-layouts.42897.x6.nabble.com/Death-By-Audio-Fuzz-War-tp2760.html

[duck_arse]

well, the 4 transistor version I saw was "a big muff pi". anyway, you seem to have no V+ getting to your collectors. check each stages collector resistors, both ends, see if you can find where V+ disappears.

have a look at the muff schems at kit rae's site, see if your circuit looks like that. you'll see that the stages are nearly identical from in to tone section, so the dc voltages around each stage are usually identical.

[edit :] and while that vero layout you posted has all the transistors (2n5089) drawn facing the correct way, they all have their pins labelled wrong. the collector is to the top in each case. the layouts seem to be missing the bias resistor base-to-ground seen in the muffs, which might mean the high gain 5089 won't bias right.

[ another edit :] another look at the datasheet says the transistor pins are labelled correct for orientation. but - why are all the npn's connected with their emitters more positive? are they all reverse beta-ing? and the single bias resistor connects hard to V+, not to the collector as expekted.

draw the circuit.

[Xplorervoodoo]

From what I understand, the transistors are reversed.  Apparently, that's a Death By Audio thing, as it seems to be common in their fuzz circuits.  It was one of the reasons why the 5089 version seems to give people so much trouble.  That's why I used the suggested 3904s in my build, as they were reported to be much more consistent.  I'll do some resistor checking, though, thanks for the tip.