As specified by the Eimac application note (AB21), 100 hours is with
power being delivered. This is standard for Eimac and most other
brands of power tubes, to keep filament set at the datasheet values,
then if you want to later reduce it to extend emission lifetime, do
so after that 100 hour run in period. They have never recommended 100
hours of just filament power. They recommend a short time of filament
only operation for all power tubes that haven't been operated
recently, usually it is 30 minutes or so, but some users run a few
hours. This enables the getter to do its job before HV is applied,
for those stray molecules of whatever gas might be present.
>Did he mean to do the 100 hours with or without plate voltage and
>drive applied?
>
>Bill, W6WRT
Ian suggested:
>Well there's a little project for you, Bill. Can you leave the hi-pot
>tester on while running up the heater, and graph the leakage current?
>
>73 from
>Ian G/GM3SEK
Only works if you have biased the grid (or cathode in some 8877 amps)
to put the operating point suffiently in cutoff. Hi Potters don't
like more than a few mA of current before they trip off. If you try
this test with just filament hot and no other voltages, there may be
enough anode current to trip off the test.
73
John
K5PRO
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