Appears that the tube has become gaseous and is now arcing with pieces of metal or oxide. The getter bloom seems to be white indicating this... tapping just makes for loose pieces to become part of the high voltage arc. Usual voltage on these tubes is 450 plus volts at tenths of amps.... I do not think he would be done in by this!
The tube on the right seems to be operating correctly even with the blue glow!
73 Mechanic
But could he get zapped doing that?
If by "zapped" you mean "shocked" - as long as he doesn't tap so hard he shatters the glass and his finger comes in contact with the plate itself he probably won't get shocked. If there are other sources of voltage that we can't see inside the equipment, he might get shocked from them if he's not careful.
Your original question was whether he'd get "electrocuted". If he's unlucky enough to allow a current of a few hundred milliamperes pass between his two hands, he quite likely will get "electrocuted", meaning killed. If he's luckier, he might only get a severe (non-fatal) shock.
If he gets such a shock and jumps backwards, crashing through a 15th story window, his death will be the result of the fall, not of the shock.
So your saying its safe to touch the tubes inside a amp when its running?
Not safe at all as these were not meant to be handled when operating....
Two good reasons were the high temperatures and the possibility of getting "zapped"! A beauty not meant to be touched but listened to or viewed!
many audiophiles like to keep their tubes in the open because of the warm glow of the heaters and the blue rays of the electrons reacting with the glass and metal impurities! :w00t:
73 mechanic
So your saying its safe to touch the tubes inside a amp when its running?
Ya see those metal cap/springs hold those tube in place? Well; if that tube voltage doesn't jump to those and ground out - then what chance does your finger? Don't you trust Beetle or CK to tell ya the truth? You should - IMO.
I still have a MesaBoogie 50/50 amp with 6L6GC's in it. Many other amps over the years. Fender, Marshall, Vox - etc. Never once had a problem touching a tube. You will get your finger burned from the heat if you keep it there long enough; but who would want to do that?