Help: Volume Pot Hiss, Fetzer Valve

[thehallofshields]

I'm looking for a little troubleshooting advice. Months ago, I built a bypassable circuit at the output of my pedalboard: a Fetzer w/ AMZ's SWTC 2 before the Volume Pot and a switchable Ruby at the Output. The simple combination is absolutely amazing. But I've run into a minor problem.

Recently, I've noticed a Hiss when the Volume Pot is rotated anywhere below 100%. No change from the Tone Control, No Change when I turn the Guitars Volume, No Hiss when Bypassed.

I expect the Pot to be the problem, but before I start messing with my beloved Pedalboard, I'd like to hear what more experienced builders think might be the problem.

Thanks,

-Matt-

[GibsonGM]

Does the volume operate normally otherwise?

A dirty pot then? 

Solution: clean it with electronics cleaning solution.

[PRR]

Some more clues would be useful.

What pot value?

And is it driving a LM386 directly?

What kinda load can the SWTC drive?

[thehallofshields]

Does the volume operate normally otherwise?

A dirty pot then? 

Solution: clean it with electronics cleaning solution.

Yes it does. But the noise doesn't come from turning it. It's just background hiss when it is set anywhere under 100% Strange?

[thehallofshields]

Some more clues would be useful.

What pot value?

And is it driving a LM386 directly?

What kinda load can the SWTC drive?

1.) 100k Audio

2.) No I have the 386 on a DPDT Toggle switch, the noise problem is there when the 386 is bypassed.

3.) I think it's expected that the SWTC2 is going to be loaded by a a100k Volume Pot. Rotating the Tone Control has 0 effect on the Hiss.

[thehallofshields]

Okay, got around to peeling my beloved pedal board apart. I found that not only was the Pot bad, but the output cap was shorting and 6V's were across the Pot.

Somehow... even with the Transistors Source reading 2V the circuit still sounded good... actually great. Can't find my solder right now, but I can't wait to get this thing back together.

[thehallofshields]

OK. Not as bad as I thought. I had the Volume pot following an MPF102 Buffer, but I forgot the Output Cap.

Fetzer now sounds good, but is getting less than Unity at full Volume. I must have done something poking around in there.