Troubleshooting my Mark III

I've got a Mark III blue stripe head that is giving me some issues. I have zero knowledge of fixing a head.

I turned it on and I could barely get any distortion out of it. Tried troubleshooting everything I could from disconnecting my EQ in the FX loop, different cab, etc. Started to fiddle with the knobs and sure enough, when I jiggled the treble knob things were back to normal. That worked for a few weeks and now it's back to no distortion. Took it apart, fiddled with the pot. I touched it with a screw driver (probably not the best idea) and it immediately worked again. If I just leave the screw driver in place it sounds fine.

I'm I looking at a new pot replacement here? A short in the wiring?

Thanks.

It could be just a dirty pot. Did the pot produce "scratchy" tone when you turned it back and forth? If so, you could try spraying it with tuner cleaner/lube. It could also possibly be a cold/broken/intermittent solder joint. Mesa pots are very good quality and I've never had an issue with one. But the amp is older, so maybe some dust got inside and is resulting in a partial connection with the pot's wiper. If the pot makes a scratchy/staticy sound through the speaker when you turn it, then I'd try using some tuner lube such as Caig Deoxit Faderlube.

I know you believe the issue is related to the volume pot, but have you tried changing/swapping the preamp tubes? It could be a bad tube,so that's the first thing I'd try.

Good luck.

Here are a few pics of the treble pot for reference. I'm not seeing any broken wiring but I'm not an expert.

I've had similar issues with the master pot on my MK III.

A good contact cleaner helped and I'd reflow the solder joints just in case if the problem does not improve. The screwdriver fix suggests a short or weak link somewhere in the wiring.