The day before Thanksgiving I was
listening on 160 & lightning hit close to
the antennas. Heard a sizzle in the shack
and lost a few things. Guess Polyphasers
in the coax and a good ground isn't enough
to dodge the bullet.
Among the things damaged were the LP-100A,
the P3 Wattmeter, Computer BIOS, GPSDO and
now I find the grid metering is not
working on the Alpha. When putting the amp
to the load/tune settings I have written
down, it performs normally and my signal
report was 59+ with excellent audio.
All the other meter functions are working
as before but not the grid metering. When
I transmit the grid goes to .7 MA and
stays there unless I increase the input
power significantly and then it raises.
Adjusting the load does not affect the
meter but if I increase the load out of
limits, the ALC meter does light and then
goes out when I back off the load. It
appears the ALC is still intact.
I'm not enough of an engineer or tech to
adequately understand the schematic, but
looking at circuit board CB-2, the control
board, I see Q202 & Q203 as well as a few
diodes are in the metering path. I have no
way to test the transistors but they are
inexpensive enough I can just replace
them.
I made a 3 page PDF of the schematic for
the push switch for grid and the control
board.
http://doctorgary.net/grid-circuit.pdf
The entire pdf manual is here at Alpha RF
systems
https://tinyurl.com/sndumoa
Any suggestions for what I might check
would be greatly appreciated.
73,
Gary
KA1J
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