[Amps] Looking for Alpha 87A expertise

Steve Thompson g8gsq72 at gmail.com
Sun Mar 14 15:16:19 EDT 2021

> 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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