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[AMPS] SB-1000 mods?

To: <amps@contesting.com>
Subject: [AMPS] SB-1000 mods?
From: Mike" <W4EF@dellroy.com (Mike)
Date: Fri, 7 Sep 2001 18:43:10 -0700
Hi Tom,

Is there any reason that a glitch resistor is preferred over a fuse in the anode
lead. I opened up my L-7 power supply last night and found that someone
had replaced the 0.82 ohm glitch resistor with a fuse (I was planning to replace
the 0.82 ohm resistor with a 50 ohm 50 watt power resistor as per the
recommendation on G3SEK's website).

Thanks!

Mike, W4EF..........

----- Original Message ----- 
From: "Tom Rauch" <w8ji@akorn.net>
To: "Vic Rosenthal" <rakefet@rakefet.com>; "Ian White, G3SEK" 
<g3sek@ifwtech.com>; "Phil Clements" <philk5pc@tyler.net>
Cc: <amps@contesting.com>
Sent: Friday, September 07, 2001 5:11 PM
Subject: Re: [AMPS] SB-1000 mods?


> 
> 
>  work, but thousands are in use. I have always added
> > Rich's grid fuse resistor scheme when repairing SB-1000's.
> > No tube failures to date that I know of.
> 
> You'd be far better off to use a HV glitch resistor, and leave the grid 
> grounded. Resistors in grid leads are bad news unless there is 
> good reason to add them, because they let the grid rise to anode 
> voltage if there is a fault.
> 
> If the grid rises to anode voltage, the grid naturally no longer 
> shields the filament from the HV surge. That means the filament is 
> many times more likely to rise to B+ rail.
> 
> Better to simply put a proper surge resistor in the HV lead, and let 
> the arc pull the anode low through a series resistance!!!
> 
> 
> 
> 73, Tom W8JI
> W8JI@contesting.com 
> 
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