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Re: [Amps] Looking for Alpha 87A expertise

Subject: Re: [Amps] Looking for Alpha 87A expertise
From: Benjamin Deovlet via Amps <>
Reply-to: Benjamin Deovlet <>
Date: Mon, 15 Mar 2021 02:31:56 +0000 (UTC)
List-post: <>
From my design experience, the 1N400X diode is much much slower than PIN 
diodes.   Ben, W6FDU In a message dated 3/14/2021 7:16:26 PM Pacific Standard 
Time, writes: 

How fast is a PIN diode?  How fast is a 1N4007 in an Alpha 87? If you 
have not measured their speed, how can you make that statement?

Jim W7RY

On 3/14/2021 7:59 PM, Douglas L via Amps wrote:
> 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 <> 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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