[Amps] AL80B power meter not working

[Carl]

The 1N914 is not a Schottky, just your basic silicon signal diode, sort of 
the 1N4148 grandfather.
If you want Schottky try the 1N5711.

Carl
KM1H


----- Original Message ----- 
From: "John DiLorenzo" <john.dilorenzo33 at gmail.com>
To: <amps at contesting.com>
Sent: Wednesday, November 12, 2014 8:19 PM
Subject: Re: [Amps] AL80B power meter not working


> 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 at 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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