My 1964 Super Reverb has volume drop....any thoughts?

[ryanm74]

I have a 1964 Fender Super Reverb. The amp sounds great except that after playing for a little while, the volume drops. Then it kind of goes between normal volume and dropped volume intermittently. I do not mean like tremolo, the amp goes down in volume for 2-20 seconds or more. I tried new tubes (power and pre-amp). I tried a different speaker cabinet. I will probably take it to an amp tech, but thought I would see what people here thought first. I know how to solder, but I do not have enough knowledge to diagnose a problem. Any help would be appreciated. Thank you in advance.

[M Fowler]

Did you change out the tube rectifier?

[ryanm74]

Thank you for the quick reply. I did try another rectifier tube, but still had the same problem. There have been times I thought I had it beat, but if I play long enough it is always there. It seems like once it starts happening, it becomes more frequent. It usually does not happen til I have been playing for a bit. There are times it does it immediately. The volume drop is not huge. Once in a while it is doing it when I first turn it on, and becomes louder. That is always a surprise. Not a lot of pattern, although it does seem to have a tendency to do it more after the first time it drops.

[Firestorm]

Three things you might try: clean and retention the power tubes and rectifier tubes sockets (drain the caps first); reflow the ground connections along the brass ground plate (this is non-trivial and takes a big iron -- check all the other grounds, too); dip a q-tip in contact cleaner and give the input jacks a good cleaning. Fourth thought: pot cleaner/lube, especially the treble and volume pots.

[rdjones]

I suspect something in the speaker jacks.
Try plugging into the extension jack and plug a dummy (OPEN!) into the main.

rd

[ryanm74]

I appreciate the replies. I have used deoxit on all the jacks before, but have not taken most of the other steps mentioned. It might be as late as the weekend before I can really do much with the amp. I am looking forward to trying all of the above. I am hoping I do not have to take it in right now.

[Diablo1]

Try taking some voltage meaurements when the amp has the volume drop.
And some other ideas too.

http://www.geofex.com/ampdbug/lowpower.htm

[Gibsonman63]

Does it produce static when the volume drops? If so, check the 470 ohm plate resistors on the power tube sockets.