On edit: refering to another of Nigels posts, these are probably American terms. In the UK I think we just used LT, HT and GB to refer to the three supplies.
How about the old black and white tv with a dim negative picture,
1) ground the tube cathode
2) connect a 15w pygmy bulb between B+ and tube grid, until you see pretty fireworks inside the tube neck
3) remove bulb and ground link.
Much of the time, you would get a useable picture, often for as long as a year. Sometimes you'd get nothing, having taken all the cathode coating off, but then, the tube was shot,anyway.