Peavey 6505+ Lead Channel Post Problem

GussyLoveridge · Dec 4, 2014

Hey Folks -

Working on a 6505+ head.

Issue: Starting at fully counter-clockwise - the Post pot on the Lead Channel gives a volume increase from 0-2. From 2-4 the volume decreases and around 5 or just before it jumps back up to real loud.

I have replaced that pot with one sourced from Peavey but the issue remains. I'm fairly certain it is not a problem with the potentiometer itself.

Any suggestions?

Thank you kindly for any advice you can offer.

Best,

Gus
Cape Breton, Canada

PRR · Dec 4, 2014

If it is not the pot, then it matters what the pot does electrically.

Link to schematic?

GussyLoveridge · Dec 6, 2014

Working on getting a schematic - they seem quite hard to find online, going to try and order one from Peavey.

JohnRoberts · Dec 6, 2014

GussyLoveridge said:
Working on getting a schematic - they seem quite hard to find online, going to try and order one from Peavey.

While you are at it you might describe your symptoms to the service department, they might have heard it before.

JR

12afael · Dec 9, 2014

that strange behaviour makes me thing of HF oscilation. the post pot it is like a master knob.

you haven't touch the output transformer? if it was replaced maybe you put the primaries backwards. you could try to cut the feedback wire to check.

I would put an oscilloscope at the output and check if you can see the oscillation.

good luck.
Rafael

buckethead · Dec 9, 2014

Hi there,

here's the schematic. The 5150II and 6505+ are the same amps, had both amps on the workbench.

Could be the relais after the post pot, if the clean/crunch channel works without problems?

Best regards,
Mathias