Yes the tubes light up.
The original problem with this amp was that it would work fine and every now and then gradually start humming. The hum would get really loud and then the fuse would blow. That's happened 2 or 3 times in the last 3 years I've had the amp. But recently, it started happening more frequently, and I'd turn the amp off before the fuse blew. The last time that happened, I noticed one of the tubes got really red/orange. I switched the tubes around to see if it was a tube or an issue with that location and none of the tubes repeated the intense glowing, but one channel stopped working. It came back on for about a minute but then went out again and that's where I'm at now. I also tried flipping the wires from the preamp (ruled out a preamp issue), and also tried flipping the speaker wires (ruled out a speaker issue).