Help needed to diagnose 5G9 Tremolux problem

[Moid]

A weird thing started to happen. While playing the volume would gradually fade away until I could barely hear it. Then it would suddenly swell back up to full volume again for no apparent reason. Sometimes it does not do it at all and other times it cycles up and down at will. All the tubes are glowing and nothing appears out of whack. I haven't checked voltages yet as I was hoping for an easy fix. Could it be a bad rectifier? Anybody have any good ideas or areas to concentrate on? Any help would be appreciated.

thanks,
Moid

[Enzo]

The tubes are glowing now, but do they stay well lit WHILE the sound goes out?

[Moid]

They are glowing when the volume dies, but I'll do a good check with the lights out to double-check the amount of glow with sound and when it dies off.

[Bruce / Mission Amps]

I agree with Enzo that you should check out the filament supply to all the tube sockets first.
Sometimes, when you think you can still see tubes glowing, ... this is from one of the two wires to the solder joints on the 4 and 5 lugs (filament lugs) of the 9 pin sockets not being connected well.

[Moid]

Problem solved

I turned the amp on and couldn't get it to come up to volume at all. I was checking the filaments and everything looked good. I was having trouble seeing the glow in one of the EH 12ax's so I swapped it with another good tube and still no go. I then switched the V2 and V3 tubes and boom, it came to life. I guess the V2 tube just had a poor connection on one of more of the pins. Thanks for the suggestions. Time to jam!