I have some kind of force field that seems to knock out the reverb in my amps. I got a used TSA5TVR amp and it really is a great little unit. The other day the reverb quit. I tested the tank by pulling the return line, putting my finger on it then turning up the reverb. No hum whatsoever. To double check I swapped in the tank from a Blues Jr (which I found out was compatible) but no dice. The problem wasn’t the tank. You just can’t find a schematic for these amps online. I put on the jeweler’s glasses and started scrutinizing the circuit board. The reverb is driven by the same IC the Blues Junior uses. I investigated everything, nothing looked bad. I got a zero voltage reading at pin 4 on the chip but I really didn’t know what I was looking for. I decided it was time to look at the back of the board for cold solder joints. Once I removed the nuts for all the pots I found the problem. When I pulled the board the pots for bass and reverb fell right off. The terminals had broken off at the board! Just thought I’d share in case it happens to anyone else.