[Amps] SB 220 Exploding Resistor

[Jim Thomson]

Date: Sun, 17 Jan 2016 19:48:16 -0600
From: "Dale LeStourgeon" <dlestourgeon at cox.net>
To: "'Tom Hellem'" <tom.hellem at gmail.com>, <Amps at contesting.com>
Subject: Re: [Amps] SB 220 Exploding Resistor

Tom, go to Harbach and buy a pack of their .82ohm resistors 2W ( $6).  Your
resistor did its job as it acts like a fuse in case there is a tube or other
b+ short. Many amps used something like this. I had this issue with my L4B
recently when a  tube failed.  Glad Harbach  has the resistors since
otherwise there are hard to find.
73
Dale K5AJZ

##  No, the glitch resistor is not there to explode, nor is it intended to be a HV fuse.
The glitch resistor is there to LIMIT the FAULT  current to a safe value.   The function
of the HV fuse..( or a .82 ohm 1/2 watt  carbon comp resistor)  is to  INTERRUPT the 
fault current.

##  3000 /  50 ohm @ 50 watt  ww resistor =  60 A peak fault current.   The HV fuse
will blow open in a split second.  You need both items. 

##  RL drake used a .82 ohm  1/2 watt  CC resistor, in series with the B+...used as a fuse.
Local store had loads of em, so stock piled years ago.  A 2 watt is a bit too big imo. 

##  The BUSS  HVU series of  HV fuses will open off in < 2 msecs. 

##  A  25 ohm @  25 watt  WW  will also work as a glitch resistor, but fault current will
be double.  3 kv  / 25 ohms = 120 A.     If a 50 ohm @ 50 watt  wont fit,   another option is to
use  TWO  25 ohm @  25 watt in series.  They can be miles apart, as long as they are wired in series.

Jim  VE7RF