Weird Peavey Ultra Issue

[DaveTMusic]

Hi All,

I have a Peavey Ultra 112 that I got used earlier this year. I should have just returned it but I was feeling nostalgic for the one I used to have that was stolen.

Anyway I'm left trying to troubleshoot some bizarre stuff.

The Crunch and Ultra Channel Volume controls are behaving very weirdly. Turning them down all the way does not silence the amp, it just has a strange muffling effect like rolling off tone on a guitar. Conversely, turning them up adds some bite and presence. This is not an issue on the clean channel.

On a similar note. When I plug a cable into the effects return (just the return) it cuts the signal on the clean channel (as I assume it should) but it does not do this on the Crunch and Ultra channels. I first noticed this because I use a volume pedal in the loop and it wasn't silencing the Crunch and Ultra channels.
It's like the Crunch and Ultra channels are in parallel with the loop.

I've cleaned the loop and all the ribbon ribbon cable connectors several times as well as the volume pots. I've touched up a bunch of solder joints but nothing seems to help.
I'll upload a video in a bit but any ideas are greatly appreciated.

 

[Geo]

It's hard to help without at least gut shots.

 

[DaveTMusic]

Here are some gut shots. If there are any specific shots that could be useful but are missing let know.
Thanks!

 

[midnightlaundry]

Looking at the schematic, the gains and volumes are on relays. Since both are funny, I'm thinking relay power supply.
Assuming this (schematic) is close to what you have, I'd check for the 17 volts dc at c62 and c63 on page 3 at B/6.5 on the schematic.

 

[Polski Młot]

Just curious what you cleaned the pots and connections with. DeOxit? Regular contact cleaner?
Sometimes regular contact cleaner will just remove oils and grease, and not really "clean" corroded or dirty contact points and pots.
Try some DeOxit (if you didn't) on the pots and give them a good turning.
Also hit the selector switches for the channels, etc..
In pic #5 that one solder joint next to where it says "Ultra plus preamp" on the far right of the board looks a little wonky.
Try a little fresh solder on that joint.