univox superfuzz clone problems

[Frances Rhodes]

hi everyone
I just finished building my superfuzz clone and, surprise!! it doesn't work.
I used the schematic from la révolution deux with the trimmer to tune the octave, but whatever setting, I just hear a loud hum, which is louder as I turn the volume knob down.
I drew a circuit board on eagle , checked for errors and nothing showed, then I wired everything point-to-point as I always do, but this time I had no luck.
I triple-checked everything, I can't see any short, I used my dremel to clean any solder that may have smeared, changed all transistors, and still the same loud hum.

I finally measured the transistor voltages and saw something odd, my (crappy) supply reads 15.4V, it seems a bit high to me... but the voltages of Q6 look rather wrong.
Can that come from a burnt resistor or something?

Q1
C : 6.76V
B : 0.86V
E : 0.30V
Q2
C : 15.40V
B : 6.74V
E : 6.23V
Q3
C : 9.78V
B : 5.70V
E : 5.60V
Q4
C : 2.44V
B : 3.02V
E : 2.40V
Q5
C : 2.44V
B : 3.07V
E : 2.40V
Q6
C : 2.01V
B : 1.95V
E : 1.37V

I can provide my eagle files in case someone wants to see them.
Maybe this is obvious, but I'm stuck!

Cheers

[thermionix]

Volume pot, lug 1..any chance it's connected to power instead of (presumably) ground?

[Frances Rhodes]

no, pot lug 3 goes to switch lug 2, pot lug 2 goes to blocking cap of recovery gain stage, lug 1 star grounded to input jack.
would you recommend something to check first?
don't you think my reading of the power supply is a bit high?

[thermionix]

Schematic:

http://3.bp.blogspot.com/-cBIzyse_wes/T0EHt4QmTvI/AAAAAAAAA88/Y1fbps_nMsQ/s1600/univox_superfuzz_schematic.gif

don't you think my reading of the power supply is a bit high?

Yes, if it's supposed to be 9v.  I agree your Q6 voltages look wrong, and the problem is likely around there since that's after the volume ("balance") control, which should ground out everything before it when turned down.

[Frances Rhodes]

that's the schematic i used but with a trimmer between the 22K resistors going from Q4&5 bases to ground.
i'll try to measure everything again with a regulated PSU or a battery, and see if something's different.

someone, somewhere else, said Q4&5 look off, as their base voltage are higher than the collector and emitter voltages, but i remember selecting resistors carefully to match everything as closely as possible...
maybe i'll desolder everything and measure everything again...

[duck_arse]

looks like problems from in the splitter and the rectifier transistors. what is that psu marked for voltage rating? can we have the board layout and the circuit dia YOU worked to, and pics of what you built, please?

and the biggie: what transistors did you use?

[Frances Rhodes]

ok, so, it appears that i'm a dumbass once again...
so, my PSU (which i use to test all my builds...) is a 9V DC - 300mA PSU, but my DMM reads 15.4V.

for my other builds it worked perfectly, but this time it didn't.
someone cleverly suggested i try the pedal again with a battery or a regulated PSU, which i have, i measured everything again, and tried the pedal and it works much much better, so i guess there is no need to post the new voltages...

and to answer your question, first i used 2SC1815 transistors, which i changed for BC337-25 for Q1, 2, 3, and 6 and a hFE-matched (as closely as i could) of metal can 2n2222a, then i changed Q6 to a 2N5088.

i read somewhere that one should use transistors with a gain of about 175 for best results, at least for Q1 to 5, and maybe a higher gain transistor for the recovery stage, maybe mine have a gain that is too big, i'll try to find lower gains ans hear what sounds best.

if you have recommendations, i'm interested!

cheers