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[AMPS] Fault B+ resistor fault protection

To: <amps@contesting.com>
Subject: [AMPS] Fault B+ resistor fault protection
From: measures@vc.net (Rich Measures)
Date: Sun, 27 Sep 98 12:47:01 -0800
>
>
>On Sat, 26 Sep 1998 20:39:06 -0700 (PDT) igor rosky <irosky@yahoo.com>
>writes:
>>
>>
>>reading eimacs Fault Protection it suggest this resistor for tube of
>>1500 watts or less, and a more complicated system for larger thoriated
>>tungsten tubes,
>>is using B+ current limiting resistors in 9k 3amps power supplies
>>still appropriate, 

In my opinion, yes. 

> >this would require very large wattage resistors to
>>meet eimacs 50 joule and less energy dissapation, 

I doubt that the 50 joule limit is needed for larger tubes.  
>......
>>Igor
>
>High power and cheap are not often attainable Igor!

amen, Carl.  

>At 9KV you will need several resistors in series to stay within the
>individual voltage ratings.
>225W wirewound resistors are not that expensive new; about $11 each for
>Ohmite at Mouser.
>
A problem is that Ohmite 225w rated resistors do not have a fault rating. 
   For a fault-rated resistor, one needs to go to Cesivid, Inc.  - 716 
286 7610   Or, one could perform fault  tests on non-fault rated 
resistors to see where they come apart.  .  .  My experiences with 
tetrodes with handles suggests that limiting I fault-peak to c.100 times 
the anode/plate I rating is adequate.  Thus, for an 8171, 25 ohms will 
probably do the job, provided that it does not break down during a 
glitch. 
-  later, Igor. 

Rich. Measures.  Web site:  www.vcnet.com/measures


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