Help on Thor with high pitch noise

[caspercody]

I just built a Thor using the ROG schematic, and I have an issue of high pitch noise while adjusting Q2. Here are voltage ratings with no noise:

Q1 = 6.42v
Q2 = around 8.3v
Q3 = Battery voltage
Q4 = Half of battery voltage

If I adjust Q2 down to the 4.5v, and the gain pot is between 9 and 3 o'clock I get a high pitched noise. If the gain pot is turned all the way up no noise or almost all the way down no noise (also if I turn the gain to zero, I get no volume?). I also noticed that when the bright switch is turned on, the high pitch noise isn't as loud as if I turned off the bright switch. I shielded all the wire's to the pots, switches, and jacks. I tried adding the capacitor from the IC voltage pin to ground, added the 100 ohm resistor between the IC and the 1nf and 100nf, but nothing helped. I hand wired the circuit, so tried separating wires and nothing much happened.

It does work, but I know I am not getting the full gain out of this with Q2 set so high.

 
Thanks

[B Tremblay]

How did you build the circuit (PCB, perf, vero) and what layout was used?

I assume those voltages are the drain pins?  Can you post the other pins' voltages as well?

[Scruffie]

I sorted mine Caspercody, I put a 47pF cap from 9v to Ground & a 100nF from Pin 7 of the IC to Ground, I think that may have fuzzed the tone up a tiny bit though so a 47nF or 68nF would probably be better, just used what I had to hand, it still hisses in the positions it squeeled but hiss is better than oscillation and the hiss is greatly reduced noisewise anyway, I think if I was bothered it would be possible to get rid of that too though but theres some ideas to try.

[caspercody]

I re-did the Thor using the pcb layout from the ROG site, and it is working now. With no extra noise. So, it must have been the wiring causing noise. Meaning I first hand wired it, and the wires were laying on top of each other. Some where I was getting some cross over noise.

[B Tremblay]

Excellent!  I'm very happy to hear that the problem is gone.