Rich says:
>and gas atoms contaminate the thorium, full-emission can be restored by
>operating the filament at max. rated potential for a brief interval.
and of course, old thoriated filament tubes that have 'failed' can often be
restored by by this technique - sometimes, even by over volting them for a
period.
>assured me that rheostats were not suitable for such a purpose.
Well, you wouldn't really want one in the secondary circuit for a pair of
3-500s would you? But in the primary...........
I remember back in the 60's, there was an article in 73 Magazine (when that
magazine was technical, before it got hung up on the 'new' technology of
repeaters) about a 4-1000 amp, where the author used a variac on the
filament transformer primary and a filament voltmeter. He recommended (I can
remember the quote to this day) 'Play radio engineer; wind up the Variac
slowly'. And he used a 7200 volt pole pig for the HV.
73
Peter G3RZP
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