1484 eating power tubes?

[JJ Gross]

I have a buddy who's a lifetime Silvertone 1484 fan, but he's a friend so I can look past that.
Lately he says his amp is eating power tubes, always the same one. I'm going off a recent phone conversation so right now details are not complete.

He says with good tubes in, it sounds great, no hum, clean, crisp, yada-yada. Then he can see a flash of light, smell smoke and the amp goes down. It does not blow fuses. I asked him where the flash came from and he thinks it was from the bottom of a power tube (base?). First time it happened, he said it hummed quietly like the output normally idles on an old amp but wouldn't pass signal. Second time, it went dead silent. He asked if he should try more tubes - I said no.

I asked him when the last time this mid-late 60s amp had new caps and he said "The caps in it are wrapped with paper", so I'm assuming the answer is never. I told him those need to go even if they look good. Would the E caps eat power tubes after a few minutes of working like this if they're bad in a 1484? I talked him through carefully looking for anything obviously scorched with no results. I also have the schematic and asked him to look for any loose wires especially the HV lines from tranny to the tubes as well as anything suspicious around the tube sockets - also looking clean so far. What else should I ask him to look at (if anything)?

I know about the dangers of working in tube amps, but I'm not sure he does. He knows there's scary stuff in there, but I'm not going to talk him through discharging caps over the phone and assume he knows what I'm taking about or even following my directions correctly. I was going to suggest the chopstick test, but I don't even know if that's a good idea at this point given his somewhat naivety. I'll probably need to get it on my bench eventually anyway.

Any ideas at what I should be looking for in the circuit given the description I have so far? When I get my hands on it that is.

Any help is appreciated.

Cheers,
- JJ

[JJ Gross]

Somethings wrong with the screens or plate voltage. Could be the bias too.

Should I expect to take a good hard look at the screen and plate resistors on this? If not those, I guess something up-stream?

I think I need to study the schematic more.

Cheers

edit :: I've been told more than once now to check the bias cap.
Considering it's age, I think I'll recap the whole thing and see what happens.