Actually, the oscillation you describe is fairly typical for a Silicon Fuzz Face, especially if you use high-gain transistors. I've had several that would oscillate as the fuzz pot was turned up near the end of its rotation.
You could try putting a 47pF (or so) capacitor across the collector-base of Q2 to see if that helps. Maybe Brian Wenz will jump in here...he's helped people with this same problem at Aron's Forum (I think it was him anyhow).
Yeah, trannies got too much gain. I messed with basic pnp- face circuit with sili BC 327 trannies, the same problem was there. Thus, I didn't bias the whole set.
One way to decrease the gain a little is to put a 100 - 220 ohm resistor off of the emmiter of Q1 or Q2. Some people say that putting a 2K fuzz pot instead of 1K helps, too [probably have to re-bias Q2 collector if you do that....]
Yeah, si Fuzz Faces have that problem alot..........sometimes I've put a lower-gain tranny in Q1 and things have sounded better. Most stock silicon FF's use the same trannys for both positions [high gain] so the problem is automatically there. Or, just don't turn the fuuz control all the way up!!
