Express volume pot NOISE

[DaveWell]

i got an Express that I built and now the volume pot make noise when i adjust it...
tube issue ?
bad soldering,
missing ground...

I put a PEC" in

Thanks for your help

Dave

[Colossal]

Check the tone stack treble cap for DC leakage.

[DaveWell]

Thanks I'll check that

[pdf64]

As a vol control is advanced from min, oscillation can cause a thump then rustling noise.

[DaveWell]

The sound is a scratchy noise...
sound like a dirty pot.

The thing is that the pot is a sealed PEC... the expensive one... and the amp have not be in dusty environement.
But... the PEC can be broken for some reason...

THanks ALL!

[joeboo88]

Hey Davewell. It’s like Colossal says, it’s probably the silver mica cap in the tone stack letting DC in to the volume pot.
It’s happened to a lot of us..
show us some pictures of your build cause we like that

[dartanion]

Doesn't matter what brand of potentiometer it is, they can still be bad. In fact, I ordered a bunch of PEC pots a few years ago in different values, and the whole bag of 50 1M Pots were bad. Every single one was open. All the other values worked fine, these not so much. Got a refund, but still need to take into account that these things happen. Swapping out the treble cap is common on Express/Liverpool amps. Give it a shot. Easier than replacing the pot.

[Mark]

Have you measured any millivolts on the top of the pot?

It doesn't take much DC voltage to make the pot sound scratchy. Are you using shielded cable on the wiper?

If not, I'd recommend it.

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