Tremoverb reverb problem

[jeff]

After about 10-15 min of playing, my reverb disapears on both channels. After about 10 min of cool down time, the reverb returns. I changed the tubes and tightened the pins in the tube sockets to no avail. Any ideas? Thanks.

[Enzo]

Isolate the problem. Is the drive going away? Or is the return going away?

If the return, it should be simple enough to trace it down. If it is the drive end, is there signal at the plate of the drive tube? Is there even B+ there after it fails? Possible bad reverb drive transformer.