Solved a reverb feedback problem read on to be enlightened.

[Music Fox]

Amp- 1976 Garnet Session man made by a Canadian company from 60's-80's. This one's reverb was feeding back at settings higher than 3 or so. Not tube problem as good tubes were tried. Foam, tank bag vertical. horizontal to no help. Turns out the cardboard base cover was foil shielded and was contacting a piece of the reverb spring suspended assembly thus shorting I guess. All I had to do was flip over the tank. For good measure I put electricians tape where the rubbing was clearly visible. Might be helpful to others.

[Mark Black]

Thanks for posting. Always nice when someone passes along a tip and/or confirms a resolution to a problem that might help some future web-surfer.

Don't know if you already tried it, but many times you can gain some clearance by moving the suspension springs to a different mounting hole (on Accutronics-type tanks at least).

[Chuck H]

In smaller "head" style cabinets the reverb location (especially the in/out jack locations) can be critical to avoid hum and noise. In this case it may be better to just elevate the reverb tank on spacers above the shielded cardboard to minimize location changes to the components.

Incidentally, the spring making contact with a shield absolutely will not cause any electrical or electronic issue whatever as the springs and their connections are strictly mechanical devices and isolated from the circuit. It is possible that there was an acoustical noise issue due in part to the springs making contact with the shielded cardboard. But it has nothing to do with the fact that the cardboard was shielded, any ground plane or other electrical or electronic issue.

JM2C

Chuck