I have doubts about replacing those PIN diodes with 1N4007’s. The 1N4007’s
don’t switch quickly enough to substitute for a PIN.
73,
Doug/WA1TUT
> On Mar 14, 2021, at 3:16 PM, Steve Thompson <g8gsq72@gmail.com> wrote:
>
>
>> 2. Is a drop from 900V open-circuit to 730V typical when
>> disconnecting/reconnecting the "R" bias lead at the HV board? I'm wondering
>> if I have another leaky PIN diode or cap to ground that is loading it down.
>> It doesn't take much to load the bias supply given that it inherently has
>> 880k of series resistance.
>
> I don't know the 87A circuits, but assuming the 900V/880k supply is loaded
> with a reverse biassed diode with 3.9M across it, the current in the 3.9M
> will drop the voltage to a calculated 734V - close enough to what you're
> seeing so I'd guess it's ok.
>
> I'd hazard a guess that the 3.9M resistor(s) are there to try and avoid
> problems from static build up.
>
> Sorry, can't help with anything else.
>
> Steve G8GSQ
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