well that suggests something is wrong but the glow in tube itself, fine. Depends on what the source is, if your hammering on the amp, and the tubes glows blue/white, that is the screens taking some abuse. Normal you would say but shows that you are being hard on it. Blue arcing lighting = **** is going to die, that is something electrically arcing. Deep Deep Red color = red plating, exceeding plate dissipation limit.
my brand new Sovtek KT88s in my 100w head i've recently had retubed glow blue like crazy. never seen such a vivid glowing before.
Yeah, just one is doing what Niff described.
Amp has been fine since the day after I got it back from the tech. Played a gig with it and everything.
When the tech had it, he reconnected this inductor in the EQ section (may have been for the graphic EQ), and replaced two screen resistors.
Sadly, tonight Catapult was going to rehearse, but one of the guitarists now has a broken amp. :/