Wild Scratching and Popping

[I.M.Noone]

Hi all, I have a mid-'90s Ampeg J12R (Reverbojet) that I REALLY love. Something is going on with it and I'm not sure exactly what to replace to fix it. Most times if I turn up its volume past 9 o'clock, the volume quickly DOUBLES, or halves and pops is very staticy. If I jiggle the volume pot around a little, its fine, but only until I let go and hit another note where it does the same thing. To confuse things, if I put a distortion pedal in front on it with the pedal's volume down and the amp's volume up, it's fine.
My first idea was that it was the volume pot, but I 'm wondering if the EL84s or 12AX7 tubes may be needing replacment. I've tried using compressed air around the pot, but no luck. Thanks for your input!

[DrGonz78]

The fact that you jiggle the volume pot around and that corrects the sounds makes me initially think that the pot is just dirty. You said it is from the 90's and that would be the first thing to check. Something is not keeping in contact in that pot and it might just be dirty or bad. Your instinct was to spray air into it and loosen the debris but that does not always work. You need to know how to clean a pot w/ contact cleaner, deoxit or the contact cleaner w/ lubricant. That would be the first thing I would check and then see where to go from there...

[I.M.Noone]

Super, thanks DrGonz! I'll grab a can of Tuner Cleaner at Radio Shack.