Unfortunately, one of the kaput tubes turned out be a YU-158 pull from an
MRI amplifier. The other tube is an 8877 (9228 date code, s/n HSZ 501)
that repoortedly failed in an AL-1500. At -6000v, the anode-grid leakage
was 0uA. At +4000v anode-grid leakage was 10uA - rapidly increasing at
higher potentials.
It is my opinion that 8877 s/n HSZ 501 probably died from gold boiling
off of the grid.
cheers
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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