Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I hope this helps someone out there...Regarding the Pro185 212 issue....This O.P. along with many other older AMPs have had this oscillation/noise problem... even with inputs removed and even after volumes were re-set down to zero. I had the exact same problem and traced it to the reverb tank. I removed the tank & stock rubber mounts (which were in a state of disintegration) and then wrapped the tank in a vinyl/nogahide coat which was glued & clamped for 24 hours. I then reinstalled the tank using new rubber bushings. Tada... no more problem.
BTW shifting the mounting position slightly is called for in order to install new/tighter self tapping wood screws. use a screw with length about 1 cm in order to grab enough but not protrude to other side of bottom panel.

Excellent info, thanks.
In general reverb tanks should float in the air touching nothing.
It´s impossible, so next best solution is to have it as *poorly* coupled to the vibrating chassis or cabinet as possible.
Springs, bags, rubber grommets, sponge, all help.
By all means do not tighten its screws.

Interesting! I had wondered about "the bag" that encloses some reverb tanks. I have just acquired a Pro 185 and really like it. Short of a broken pot it seems to have no problems, yet. For late eighties solid state it sounds, well.. great!