> Wonder if this phenomena could be responsible for some of
the power tube
> flashovers we have seen from time to time? Could be the
flashover blows away the
> "whisker" and all is ok for a long period of time
afterwards.
Two primary mechanisms cause flashovers in tubes that are
not damaged. They sometimes develop metallic whiskers and
they sometimes have trace gas. Gas ingress through seals or
outgassing from materials inside the tube cause the
flashover in otherwise healthy tubes.
The arc getters the gas or burns off any whiskers, and the
tube (if not a leaker) is OK for an extended period after
that.
We used to power up brand new 3CX3000A7's to about 12kV
through a current limiting resistor to "burp" them, and then
after arcing they were fine at normal voltages. When we
didn't do that we'd have HV faults in about half the tubes
on turn on.
Vacuum capacitors can develop whiskers also. Again a
controlled current arc will burn them off without damaging
the capacitor.
73 Tom
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