Scratchy POST VOLUME pot Peavey Combo 115

[Tone Meister]

No schematic at the moment, the folks at Peavey were having trouble finding it earlier today but I have a request in over in the schematics sub forum.

The POST VOLUME pot is scratchy when turned, and it's not dirty. I subbed in another pot to make sure.

I measure -0.04V DC at the wiper with the pot turned all the way down, but right at .9V DC on the wiper with the volume all the way up. Also, I measure 0.00V DC across the pot with the volume all the way down, but measure the same .9V DC across the pot with the pot all the way up.

No other pot scratches when turned. Ideas?

[Jazz P Bass]

Peavey Combo 115 Schematic

This is what I have.

[Tone Meister]

I'm not in front of the amp at the moment, but that (2001) schematic ^^^ shows several features that aren't on the amp I have. I believe the amp I have is much older, perhaps the 70's or 80's.

[MarkusBass]

No other pot scratches when turned. Ideas?

Failed op amp just before the pot? You can check it without the schematic. But check also +/-15V rails and voltages on the inputs.

Mark

[R.G.]

Just from your description of DC voltages across the pot and wiper, the DC is coming from the wiper side. Go measure things on the wiper side and find out what's leaking DC in from there.

[Tone Meister]

Following RG's advice and keeping in mind MarkusBass' comments I was able to find an OP amp with DC on its 1OUT output. It was located at the far end of the board next to the connector feeding the power amp board.

Amp works as new and is very quiet. Thanks guys for helping me with my thinking.

[audiopete]

Yay I like threads that end with a nice solution and everyone is happy.

[lowell]

Yay I like threads that end with a nice solution and everyone is happy.

sooo… you like happy endings?