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[Amps] SB 220 Exploding Resistor

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Subject: [Amps] SB 220 Exploding Resistor
From: "Jim Thomson" <>
Date: Tue, 19 Jan 2016 20:45:39 -0800
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Date: Mon, 18 Jan 2016 14:13:10 -0700
From: John Lyles <>
Subject: [Amps] SB 220 Exploding Resistor
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If you get a strong enough wirewound resistor, this can suffice as the 
surge current limiting resistor for a spark over in a tube. With 250 
amps at the beginning of the overcurrent (2500 V/10 ohms) spike, there 
is enough magnetic field to break a wirewound R as the windings have 
mechanical force between turns. I have always used bulk carbon for 
series R, like Kanthal Globar makes. They are exactly the right part for 

Finding them through distribution might be a problem, though. Has anyone 
else used these?


##  The energy absorbing types are the AS  series.   The SP series is what is 
used in dummy loads, etc.
I have used these real small  globars back in the 70s... for the parasitic 
suppressor in several amps,  but
I don’t remember if they were  type  AS  or  SP.   Dunno if  Globar will sell 
you just 1-2 of them ?
SP types are rated for  350 deg C.   
AS types are good for  250 deg C

##  There is no issue using wire wounds for a glitch R.... provided they are 
sized correctly.
2500 /10 ohms  =  250A.    
3000 / 10  ohms =  300A

##  2500 / 50 ohms = 50A
      3000 / 50 ohms =  60A 

##  A  single 50 ohm  @  50 watt  WW works quite well..and does not implode.  
However, I use a HV
fuse in series with the 50 ohm glitch Resistor..... to interupt the peak fault 

##  I have also tried paralleled  100 ohm  @  50/100 watt  wirewounds. 

##  Ameritron sells the globar type  AS  glitch resistor.... forget the value 
they use.   If its real low,  like 
10-15-20-25 ohms,    you could always series  2-5 of them.  But I believe they 
are not cheap.   I believe
they only sell one value. 

##  I have also tried  the bigger, tubular type  SP resistors for a glitch R, 
and they work good.   But these were obtained
surplus.  I have also tried large tubular type  AS, and they work very well. 

##  But the wire wounds are cheap to buy new, and in any value and wattage you 
want.   Readily available. 
50 ohms will limit fault current to a low value.... and is not high enough to 
cause heat issues, when used on 
high duty cycle modes.  Also, the V drop across  50 ohms, with  500-1000 ma of 
plate current is not an issue either. 

##  You will not implode a 50 ohm  @  50 /100 watt WW any time soon.  
##  surplus  globars show up on the market from time to time..and also work 
I bought several  50 ohm, 90 watt CCS  type  SP  globars, same as used in a 
heath dummy load, these also work
excellent for glitch use.  I believe ameritron also sellls em.

Jim   VE7RF

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