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Re: [Amps] SB 220 Exploding Resistor

To: "Jim Thomson" <>, <>
Subject: Re: [Amps] SB 220 Exploding Resistor
From: "Carl" <>
Date: Tue, 19 Jan 2016 17:14:37 -0500
List-post: <">>
----- Original Message ----- From: "Jim Thomson" <>
To: <>
Sent: Tuesday, January 19, 2016 2:50 AM
Subject: [Amps] SB 220 Exploding Resistor

Date: Sun, 17 Jan 2016 19:48:16 -0600
From: "Dale LeStourgeon" <>
To: "'Tom Hellem'" <>, <>
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.
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

Dentron used a pair of 1 Ohm 1/2W carbon comp in parallel as a fuse at the base of the plate choke and it was useless for an arc. They did blow when 572B's went in a run away oscillation and melted the glass.

A film resistor will self destruct a lot faster; I just replace with a regular glitch type..

Ameritron went with the type mentioned by John Lyles in their big amps, kind of expensive, and of questionable use over a vitreous enamel type. Prior to that they used nothing .......from zero to overkill IMO.

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