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[AMPS] Shunt regulated high voltage psu

To: <amps@contesting.com>
Subject: [AMPS] Shunt regulated high voltage psu
From: 2@mail.vcnet.com (rich)
Date: Tue, 29 Jan 2002 04:59:10 -0800


>
>
>On Mon, 28 Jan 2002 16:46:29 -0800 rich <2@mail.vcnet.com> writes:
>
><snip>
> 
>> >>-  1N5357 5W, 20V, DO-5 case zeners currently cost 80-cents US  each
>at
>> >>Digi-Key.  20 would be needed for a 4cx250R supply - 18 for a 
>4cx250B
>> >>supply.  The safe current carrying ability is c. 85mA - which  enough
>for
>> >>8, 4cx250s in linear service.
>
>> -  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
>
>Hi Rich,
>   Well, it may be cute to tile a vectorboard with those but, it isn't
>economic at $16.
>
>   A suitable power FET costs a $1 these days. Add another $1 for a
>voltage regulator IC and a few small R's & C's. 

- To ice the cake, one still needs a similar 400v zener string to protect 
the FET from Drain/Source breakdown.  As I recall 500V C-E FETs go for a 
bit more than $1.  Such a device also needs a heatsink. 

>Get fancy, add a trimpot
>for voltage adjust so you have "something to turn" and you have a $3
>regulator. 
>
-   And, as an added bonus, one has a high current-gain IC in an RF 
environment.  

-  I built the 2, 4cx250R 2m linear amplifier with the ancient 
Eimac-recommended screen shunt-reg. circuit (powered from the anode 
supply) 25 years ago.  It has not yet failed or failed to protect the 
tubes.  Sometimes mo' tricky is not mo' betta.  

cheers, Marv

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
end


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