[Amps] Lightning strike - Alpha 77Sx grid issue

[Gary Smith]

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