RCA 21AXP22 picture tube/rebuilt picture tube

[electroking]

Originally Posted by compu_85

I'm going to ask a stupid question here...

When a tube goes gassy like that, does it have to be rebuilt? What prevents you from heating up the nipple under the tube cap, attaching a new piece of glass, re applying the vacuum, and resealing it? From my view it seems like a lot of these tubes have very, very slow leaks, which makes me wonder how hard it would be to periodically "top up" the vacuum.

-J

A lot of gas will have gotten adsorbed (that't correct with the D) in the
electrode surfaces, and even if you stop the leaking process, continued
operation will keep releasing gas inside the tube, and the getters (already
weakened by the initial leak) will not be able to cope with all that gas.
When the tube is rebuilt, it is heated while being pumped out, and
this is done before the new getter is flashed, so that much of the
adsorbed gas is removed, and the (new) getter can do its job after the
tube is sealed. Regards.