Road King: Loud noise / hum

[Kasogi]

Hi all!

I have got a problem with a Road King II amp I just bought used:

I play for some time - everything seems to be alright. Then, suddenly, the guitar sound dies and I get loud humming noise instead. The humming does not go away if I change the channel or the power tube configuration. The only thing to get rid of it is to turn off the amp and wait for some time. Then, after some time, again the same story...
Sometimes, the humming suddenly starts when I use the footswitch to change a channel.

Is this a tube problem? Any other idea? Any idea how to systematically identify the issue?

Thanks and best regards
Sven

 

[58boogie]

any chance you are sitting right in front of the amp, with the guitar facing the amp? Does it happen if you are standing 6-12 feet away with your back to the amp?

 

[calvin1]

sounds like a power tube too me cal