You could try just keying up the amp with no drive and note the total plate
power dissipated. Something close to rated plate dissipation is best if the
cooling is adequate. Otherwise you may need to build up a little bias supply
so you can vary the plate current. If you did this, I suggest removing plate
voltage from one tube so your power supply and cooling will only be working
with one tube at a time. (Your SB220 will not be happy pumping out 1000 watts
of dc continuously). Also in the event of an arc you will know which tube did
it. Do not use a variac on the whole amp as this would reduce the filament
voltage.
These suggestions are for tubes like yours that are not known to be gassy, If
you had questionable tubes you would want to run them at more like 1000 volts,
adjustable bias, and be prepared for an arc that would blow the line fuse. You
don't really want that to be occurring with a good, working amp at full plate
voltage.
I've attempted gettering some 3-500s using a variac on the B+ supply. Bad
tubes can begin drawing a LOT of current in the range of 1200 volts. Really
gassy ones will like up like a mercury vapor rectifier in a Viking Valiant.
Rick K2XT
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|