> do I need to buy the heaters for the tubes? or do they come with the tubes?
Argh!!! I ripped my back last week, very pained, sitting here doped to the gills, and you give me the best belly-laugh I've had all week. LOL(ouch) LOL(ouch) LOL(ouch) LOL(ouch) LOL(ouch) LOL(ouch) LOL(ouch) !
Not laughing At You, but at the way some things that seem "obvious" after way too many years do have to be mentioned to someone who has never done this before. Like first (and last) time I was on a horse: "where's the brakes?"
As Arrigotti said, "very much like the filament of a light bulb." i.e. you CAN'T put heaters in tubes yourself (unless you have super high vacuum and sealing equipment). Just like you can't replace a broken filament inside a light bulb.
Look at the pin-connection diagram for the tubes. There are 2 (or 3) pins called "H". Look at the tube, squint inside. Those pins are welded to metal strands that run up inside the center of the tube. It is basically a light-bulb filament (which makes more heat than light), packed with clay (insulation), shoved inside a coated metal sleeve (cathode). Some fine wires are wound outside the cathode (grids) and then a big metal sleeve (plate). The heater is in there "forever".
Oh... when you get into BIG tubes, ones with handles, many thousands of watts, some of them can be taken apart to have the filament replaced. Obviously(?) you need a high-vacuum facility to put it back in working order. And I don't think they would ever put a tube back together without a heater: they use the heater to stir-up the last few gas molecules so they can be sucked or absorbed, and they need a heater to test the tube and be sure it went together right.
