[old_tv_nut]

2) I definitely would not leave vintage tube equipment running. Not only is there the possibility of an escalating failure, but tubes are always in wear-out mode, so having them hot when not needed is a waste. Think of all the instant-on TV sets that wore out their CRTs prematurely.

5) I think there's no way to determine phosphor type for sure by looking at an unpowered tube, but maybe someone can comment if the phosphor can be made to glow by applying a Tesla coil to the face?