Never got any answers from this reflector (too few 87A owners, or is
everyone too busy arguing about theoretical minutia?)
Anyway, it turned out that the soft fault#1 (receive PIN diode bias too low)
was caused by, of all things, leaky PIN diodes! The soft fault#18 (filament
current too low -- possible open filament) was caused by, of all things, a
bad tube!
I must commend AlphaPower's service department. In spite of all that's going
on there, I got terrific help. Even though Karl, the 87A expert, was away,
Glenn AE0Q, was able to help me. He emailed me troubleshooting instructions
that definitively diagnosed the PIN diode problem, then overnighted
replacement PIN diodes and tube. I was able to replace the PIN diodes
without removing the output T/R board (a bear to do), by soldering them in
from the top. The amp was ready for CQWW SSB, and performed flawlessly under
heavy action.
Still a great company...
73, Dick WC1M
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