> From owner-amps@contesting.com Fri Dec 5 11:30:12 1997
> Greetings,
>
> I'd like to know if their is a reliable way to test the emission of
> the power tubes we hams generally use. Tubes like CX800s, 8877s etc.
> without having to actually run them at full power in an amp.
>
> Would a simple test fixture (inc. cooling) with the appropriate voltages
> on the tube elements measure to transconductance do ? Would that be
> expected to correlate with performance under full load ?
>
> Thanks
>
> --db--
I know of a company in the UK that can 'test' most tubes. The chap was quite
helpful and agreed to test a 3CX5000A7 for a nominal cost (about 35 pounds)
if I did not mind waiting until he was not busy. The 'test' would be performed
at low voltages/currents, and full power performance extrapolated from there.
I was a little suspicious of this method, so contacted Eimac to get a quote for
testing, while also asking a ham I know there about the validity of testing at
low power. He thought that testing at low power would be sufficient to tell if
the vacume was okay, but not good to test how much power the tube would produce,
which depended on the peak emmision. I was told that Eimac would pulse the
catode current, and was told 50A would not be abnormal for a 5 kW tube.
Unfortunately,
Eimac were unwilling to test a tube at a reasonable cost (they quoted me $450,
plus carriage), so my tube has not been tested to date.
G8WRB
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