SWR PB-200, What gives? Help!

[Starrla1000]

I have an older SWR PB-200. Well built, nearly point to point, heavy PCB, and good-clean-wiring. There is a single 12AX7 in the pre section, and a solid state power section.

The problem is this; very low output, tin can tone, and everything looks great on the inside.

I retouched all the solder points on the preamp board, made sure nothing was loose or coming undone. All controls work (doing something), and when the gain pot is turned, the amp sounds like it will almost work. It sounds like there is a big glob of dirt in the pot and the contact is always stuck on the glob. I don't hear the typical crackle of a dirty pot, but was wondering if the gain pot could still be "bad". It's a real bitch to remove the single pot because ALL the pots AND eq sliders are directly holding the board in place, meaning to replace one - it all has to come out, seems like there are 50 or more ahh!

Before I do this daunting task, are there other things I should look for?

[Enzo]

Yeah, try patching the effects loop with a cord - send to return. if there is a pre out and power amp in jack set, try patching those together also. if that restores the sound, you have a jack problem.

[Steve Conner]

Have you tried changing the tube? It could be worn out.

[Starrla1000]

Yes, I have changed out the tube, but to no avail, it sounds the same. I have not tried jumping the pre to power, or effects loop yet, but will. Perhaps doing so will show some result. Can individual pots go bad? I kind of think that the first pot in line (gain) has an issue. That may be the problem. I just hate to pull it all out to find out it's just a little thing that can easily be done. Any thoughts?

[drewl]

I've got one that oscillates like crazy!
Something about that FET on the input, BUT it had at least 3 bad pots, they help hold the front panel in place and the tabs broke away from the housing but you couldn't tell without taking it apart.

Never got around to fixing the preamp, I use it as a monitor amp backup.