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[AMPS] HV Fusing / Diode Protection

To: <amps@contesting.com>
Subject: [AMPS] HV Fusing / Diode Protection
From: 2@vc.net (measures)
Date: Mon, 12 Jun 2000 11:04:51 -0700
>
>
>In the L4-B power supply, Drake used an IRC type BWH/SPH "fail-safe" 
>resistor (0.82 ohms/2W) as a fuse to protect the diode strings in the 
>event of 
>a short or closure of the RF deck cabinet interlock. 
>
>The resistor is still a current IRC product (as a type SPH device), but is 
>not a 
>high demand item, and is out of stock at every IRC distributor I have 
>checked 
>(including Drake).   So while it is "available" it is essentially 
>Unobtainium.  
>Newark wants a minimum order of 250 each to even go ask IRC for a 
>production run.  At $0.44 each, that makes a pretty expensive price for
> ONE ;-)
>
>So the question.  Is there some generally accepted alternate method for 
>protecting HV diode strings?  

Yes.  The ''glitch'' resistor.  A glitch resistor limits fault current.  
It is not a fuse.  It must be able to discharge the hv supply filter C 
without sustaining any damage.  

> A wire fusible link, perhaps? 

A fusable link does not limit peak fault current - and that is the thing 
that causes damage.  The right place for ordinary fuses is in the 240v 
line.  

>Or is this even 
>considered necessary?  

A glitch R is totally unnecessary if you have a free supply of new tubes, 
Grant.   cheers


-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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