[sdiy] tube repair

[Travis Shire]

> >You can't repair a broken tube. Even if it *was* possible...it would be
cost
> >prohibitave. The getter is flashed with RF energy after the tube has been
> >vacuum pumped and sealed.
>
> It's worse than that. Once O2 hits the emission coating on the cathode
it's
> ruined.
>
Good point. I was thinking that the filament would be contaminated and would
need to be replaced, but I forgot about the cathode coating. Nice catch.