New amp and now something like this
:
Played guitar as usual and suddenly my amp started to hum. It was like a feedback. I turned back the volume immediately but no difference: the hum didn't stop. So i switched the amp off.
5 minutes later i switched it on again and in the moment i turned the standby switch the powertubes glowed for a fragment of a second extremely bright and blue. Then there wasn't anything anymore, no sound, no hum, no nothing.
Is this a defect of the powertubes or can it be something else?