59 Bassman reissue cuts out after 10 minutes

[TheDevice]

After about 10 minutes the amp sound cuts off, all tubes are lit - just no sound.

I've replaced the preamp tubes, no change.

Any ideas?

Thanks!

[MWJB]

Sudden cut off, or a fast fade?

Any red plates on the 6L6s?

[Chuck H]

When you say "no sound" does that mean there isn't any sound at all? No small amount of hiss or hum?

Also, Does your guitar use a preamp?

Chuck

[TheDevice]

The sound fades out in about 1 second then no sound at all, really quick. No hum no hiss. When you say "plate" do you mean the grey part of the tube? They look normal.

I'm just playing strait into the amp.

Thanks for your help guys!

[pdf64]

Yes, the plate is the main visible part of the tube's innards.
The fault maybe a bad resistor in the power supply, plate or cathode circuits?
I think someone needs to open the amp up and get in with a test meter, but it will need to be tested when powered up.
Unless you are experienced with doing this type of thing, it might be best to take it to a tech?
The problem with finding the fault maybe getting it to fail with the chassis out of the cab, as it won't heat up as much, so might need to heat it gently with a hair drier.