Fuzz meets theremin?

I built a Dallas Arbiter Fuzz Face clone and it works fine until the the fuzz is about 2 o'clock or above, after which point all hell breaks loose.

It produces a low-pitched synth-like sound, and when I turn the guitar's volume knob up or down, I get a theremin-like sound, going from low-pitch at 2 or 3 up to high-pitch at around 8 or 9.

To be honest, it is very fun to mess around with, but I would rather have a fully-functioning Fuzz Face.

I used this layout and all parts were from Small Bear, including the matched transistor pair for Fuzz Face circuits. I also used the resistors specified for the transistors so they should be biased properly.

I measured the voltage across each leg of the each transistor, and consistently got the battery voltage (~ 8.3V) on each of them. I'm pretty sure I'm measuring them properly (black probe to sleeve of input jack, red probe to leg of transistor). I know that's a ridiculous high voltage for them, so what do you think could be the problem?

Seems like self-oscillation to me in the high gain settings.

Sorry about the long post, wanted to make sure I got everything in lol.

That company has been around for a while and I guess the circuit could be wired wrong? maybe disassembly and check all the components or partial disassembly and check? I don't know but I am going to post to bump this up top so maybe someone may see it. I am betting on a bad part or just wrong wiring. I doubt the circuit is wrong from diagram, where to start...I have no clue. I had a bad power amp and I was told it was either the caps or the transistor...that is all the old amp had in it so the advice didn't help much. Leaking cap or oscillating transistor. That is 95% of the parts, so basically what do I NOT check, resisters. But in my case the amp was already working, in your case it could be a bad resistor, so as you put the fuzz up it changes rather than a constant oscillation's like a the poser amp? On the other hand it could be the transistor due to the fact that it is what is distorting so when you turn the knob up to crank the fuzz up it gets more juice, more oscilations...I am cluesless as to what to do other than test every part:shrug: