The bias is controlled by two zener diodes (controlled by the CW/SSB
switch). Does toggling the switch make an appreciable difference in the
resting current? Most likely, you have a damaged zener.
It doesn't sound like you had an oscillation; it sounds like you had an arc
from plate to grid, or maybe a power surge. I've found these will take out
the grid resistors, zener, meter etc.
Sorry you're having such lousy luck.
Ed N1TS
----- Original Message -----
From: "Dana Roode" <K6NR@ARRL.net>
To: "AMPS" <amps@contesting.com>
Cc: "Dana Roode" <K6NR@ARRL.NET>
Sent: Saturday, November 22, 2003 12:36 PM
Subject: [Amps] AL-1200 Questions
> Folks -
>
> My AL-1200 repair efforts continue. As you may recall, the parasitic
> suppresser came unsoldered and I had some sort of oscillation in the grid
> that took out the grid resistors, a resister in the grid meter, and my
> 756ProII. It turns out it also took out my ARB-704 relay buffer, and last
> weekend the grid meter mechanism itself gave up the ghost.
>
> Questions:
> - After replacing the grid resistors, the resting plate current seems too
> low, maybe half of what it should be. Is there an adjustment for this?
I'm
> not sure why it would have changed.
> - I will order a new meter, should I put a diode across it to protect it
in
> the future? What kind?
>
> Dana
>
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