Meathead Dark Oscillation?

[skeletonghost]

Hi, first I just wanted to thank everyone for their hard work at Tagboard. I've learned a great deal about electronics from reading your website! I am trying to complete the Meathead dark from the one-knob fuzz project. I believe my layout is correct, and I cannot see any solder bridges. When 9v is applied I get a high pitched oscillation.

I have built the circuit twice to double check my work. The first time with metal film caps, and this time with mono caps. I had the identical problem each time. I have tried the circuit with 2n3904, 2n2222a, and bc550 with no luck. I suspect the input and output are cascading somehow? Any ideas would be greatly appreciated!

[skeletonghost]

Here is a video of the strange oscillation. This would almost be cool if I had been intending to make an oscillator http://youtu.be/EKevEbtotso

[Vince]

Can you try it with a battery to rule out a noisy supply. Also, sometimes noise can vanish when you box fuzzes. Less interference I guess.

[skeletonghost]

Hi! Thanks for the idea but I have only connected it to a 9v battery supply so far. I will try to case it and update if anything changes. Any other advice would be greatly appreciated!

[skeletonghost]

Hi, just got it in a case with a 3pdt and no change. I'm really stumped on this. The circuit is verified and fairly simple. I also tried my bench power supply and still got the same oscillation.

[IvIark]

I always get some oscillation in silicon Fuzz Face type circuits at higher gain settings when the circuits are unboxed, but never anything like that.  In fact the only time I ever did get oscillation like that I had the polarities reversed.

What voltages are you getting at the transistor pins?

[skeletonghost]

Hi IvIark, here are the readings at 9v with 2n3904 in Q1 and Q2. Thanks!

Q1: C(1.35) B(0.65) E(0)

Q2: C(4.74) B(1.34) E(0.9)

[skeletonghost]

Doing some research in the comments section of other Meathead layouts on here and found someone with very similar results:

Jim Cook wrote

Here we go, measured to ground the values read thus

2N3904 E - 0
B - 0.62
C- 1.57

BC182L B - 1.57
C - 3.87
E - 0.91

his description of the problem is similar too  "Right I found that i hadn't got a connection between -ve terminal of the battery snap and ground so i added one and there is now a ground to the circuit, the led now comes on but still no sound other than i hight pitched warbling or a hum depending on if it's switched on or off."

Oh well I guess it's just a difficult build. I'll start over. It's weird how this seems to go smoothly for some and difficult for others. I dunno if it's parts or what.