A couple of other pieces of information on this problem:
No oscillation occurs when the input is connected to a
50 ohm dummy load. It does occur with a 50 ohm dummy
load on the output and the input either connected to a
transceiver (with no drive) or if the input coax is left
disconnected from everything. The oscillation disappears
when the input is shorted.
I found this interesting -- while trying some different
tests with the amp, I noticed a high pitched sound coming
from inside the amp. After powering back up with the
cover off, then keying the amp (again, no drive), I saw
violet light shining through the ceramic of the tube,
just below the anode cooler. The light, sound and
abnormal grid current and power out all occur and disappear
together.
Now what?
73, Arliss W7XU
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