Biasing the fuzz factory

[::::FLARE::::]

I have made a fuzz factory clone, with ac128 as germanium transistors.
It sounds great, and very similar to the original (I can compare only with online demos, I've never tried an original pedal).
the only thing that differs, and I've been unable to fix, is that at maximun drive settings (I mean at the really end of the range of the pot, the last 2 mm...), it self oscillates, even with the stab full clockwise, and gest very very noisy. I know it's not a quiet circuit, but the original doesn't seem to oscillate at all.
I tried any hfe  for the silicon transistor between about 45 and up to about 200. the sound changes, but the problem remains (by the way, I found out that it sounded best with lower hfe for the first tranny).
I also tried different combinations for the germaniums (I have ac128s with hfe of about 40, 80 and 110). Again, no way to get rid of the oscillation at maximum drive settings.
So, I've read on this forum and on others, that there's no needing to bias the Fuzz Factory, as the controls act themself on the bias of the transistors, but in my case, it really seems a biasing problem....
Any ideas?

[RandomGlitch]

It sounds like a connection somewhere is wrong or missing. Or maybe one of your components is wrong so that it's not possible to bias it correctly no matter what.

[chromesphere]

Prehaps you could do the tone bender trick and add a resistor to the pot to, basically removing the oscillating part of the drive turn?  Prehaps thats what zvex does?  I have built 2 fuzz factories (both with different transistors) and they both self oscillate on the last part of the drive turn.  I found that the tone bender behaves the same, not sure if its for the same reason, but the behaviour is almost identical. Last 10% approximately goes into noise / oscillation.  For the Tone Bender, this is normal behaviour.
Paul

Edit: http://zvex.com/phpBB2/viewtopic.php?t=4462&sid=8f2cd5702a1db5d5a60154c62fde6aa4

[Jaicen_solo]

I can't say i've noticed that this is a problem to be honest. I tend to have it set so that it will oscillate/intermodulate when I play, but be silent when i'm not playing. The key is to set the comp and gate just right.

[::::FLARE::::]

thank you very much guys, I feel better...    So, even mr Vex says in certain conditions the (kind of) oscillation happens with the drive full on.

I didn't know about the "tone bender trick", thank you for telling me, 'cause the tone bender will be one of my next projects !!

[chromesphere]

imo, It's a noisey, misbiased circuit and is prone to all sorts of strange behaviour.  I recently started a thread "fuzz factory now with radio stations' beacuse i used GT308V's which were picking up RF while adjusting the gate / drive / comp.  I swapped them to ac125's and the radio stations went away.

I like zvex's response, basically "dont turn the dial into the noisey part".  Bang.  Problem solved lol 

Theres actually a few threads on his site of people asking that same question "drive knob on full = noisey?"

Paul