Peavey Classic 30 intermittent fault

[Ziggy Roque]

Hello Folks,
I'm also new to this group and joined.. based on a problem I have with my Peavey Classic 30. My knowledge about electronics is limited. The problem I have is this: a few months back my amp started to drop out occasionally, usually after 20-30 minutes of playing, in a way similar to a weakening battery in an FX pedal (I use 4 pedals max, all battery-run), losing volume over roughly 30 secs to 1 minute, until no sound could be heard. This happened more often lately. Today I noticed that the power supply to the valves was dropping and slowly going off. The filaments would slowly stop lighting up.. while the pilot light remained on. - Using the simple 1st test method of kicking the amp slightly the power did come back on, but only briefly. The output valves are fairly new, the pre-amp valves not. The reverb hasn't worked in ages but that seems to be a circuit separate from the valve circuit (this I learned from this forum ..so, thank you very much. I have already learned something new..). - I should add that the amp made a rumbling, rushing kind of white noise before this new problem occured, sounding like the output valves were on the way out, but they are as I said fairly new. Does anyone have an idea what the problem could be? I have a MM but I don't know enough about what to measure where and how. I will study this matter further but perhaps someone can give me advice on what to look for. Should I replace the 3 x 12AX7s (the filaments in those remain 'on'...so that doesn't seem to be the problem, but...) ? Thank you.

[0xPIT]

Lethal Voltages inside!
Get the device to an experienced tech.

[Ziggy Roque]

Thanks for the reply. I know how to discharge high voltage capacitors, I have some experience in amp repairs so I will first try to find the fault myself . I'm hoping to get some tips as to what steps would be logical to follow, or to find someone who has similar issues with this particular amp. Most valve amps are very sturdy in comparison. I've played a Vox AC30, a Musicman , various Fender amps etc and never had as many issues as with this Peavey. The current problem, the 'delayed' power outage seems to only affect the output stage so I may be close to isolating the fault. .. Thanks for the advice though.
Cheers

[SeanB]

I will guess as the filaments go out you have dry joints on either the heater wiring, or corroded pins and sockets. First simply remove all tubes, clean the pins and sockets with a cloth moistened in IPA, and then place the tubes back into the same sockets. Then look underneath for cracked solder on the heater wiring, you could have a single poor connection on the power transformer winding or wires that has high resistance and causes this.