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[AMPS] SB-1000 mods?

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Subject: [AMPS] SB-1000 mods?
From: (Tom Rauch)
Date: Fri, 7 Sep 2001 20:11:16 -0400

 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 

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