>
>Right in the middle of the CQWW contest my AL-1500 goes bang.
>
>Thinking that I might have lost a tube, I disconnected the anode connector
>and turned the amp back on.
>
I would measure the leakage at +/- 8kV on a high-pot. tester. With pos.
on the anode and neg. on the grid, if the leakage is more than roughly
10uA, something is amiss. If the measured leakage is identical with
either polarity, the 8877 is probably gassy. If the leakage decreases
sharply with neg. on the anode, gold sputtering* is indicated, which
suggests that a vhf parasite may have taken place. Note: to the best of
my knowledge, the AL-1500 is the only 8877 HF/MF commercial amplifier
that does not use an anode vhf parasitic suppressor.
{*see "letter from Eimac®" on my Web site}
- later, Larry
Rich. Measures.,www.vcnet.com/measures, 805.386.3734
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