Thanks, that sounds like a fairly simple technique to discharge the tube. The red cable with the suction cup is obvious to me. Metal of the chassis - any metal? Being an all-wood piece, not sure what metal to ground it to.

I see the horizontal oscillator tube - the silver canister (see photo in 1st post) has a map of all the vacuum tubes and what their job is. No obvious sign of damage to it, but I have another one in this spare set that I could try.

About the whole vacuum tube thing - should they all pretty much pull straight out of their sockets, maybe with a little rocking motion to break them loose? It looks like they should, but I don't want to pull too hard and end up breaking something...