Well, as something easy to try, I replaced the two detection diodes on the
power supply board. I didn't have the germanium 1N34s, so I used some
1N914 schottky diodes that I had, just to verify if this was the issue.
And now both forward and reflected meter indications seem to be working
fine. In standby, with 100 W from my radio, the meter indicates 0.1 kW.
So, these diodes seem to be working well in this circuit. In CW mode, I
can tune to an indicated 800W into a dummy load at 14.250 with about 70W of
drive. I did order some 1N34As off of ebay, and I'll replace the schottky
diodes when these come in. But for now, I'm a happy camper.
Thanks, and 73.
John, K8DIL/AE
On Tue, Nov 11, 2014 at 11:42 PM, John DiLorenzo <john.dilorenzo33@gmail.com
> wrote:
> I bought an AL80B used and meter 1 doesn't show any forward power either
> in standby or operate. The multi-function meter will indicate HV and ALC
> SET, but no reflected power either. Trying to measure the coupler detector
> components in-circuit doesn't give me anything useful, but since the meter
> shows HV and ALC SET, I'm suspicious that there is a -12V issue; the
> forward and reflected power meter circuits include BJTs that have the
> collectors tied to -12V. I think I'll have to tack some wires onto the
> -12V, and the forward sample point on R122 on the Power Supply board. Can
> anyone tell me what voltage I should see at the junction of R122 and R125
> for 100W CW?
>
> Thanks in advance,
> John, K8DIL
>
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