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Re: [Amps] Grid fuses (was: Life and gain of 3-500Z)

To: <craxd1@verizon.net>, <amps@contesting.com>
Subject: Re: [Amps] Grid fuses (was: Life and gain of 3-500Z)
From: "Tom W8JI" <w8ji@w8ji.com>
Date: Fri, 21 Jul 2006 09:28:54 -0400
List-post: <mailto:amps@contesting.com>
> I could see this if the tube was operating and the 
> electrons were flowing between the cathode and grid then 
> back to the cathode via ground like it supposed to. Once 
> the fuse/resistor opens, the grid could be less some 
> electrons. Since the cathode is still emitting electrons 
> that are being drawn to the anode across the grid, the 
> grid would accept enough electrons to come into 
> equilibrium. I can't see it though taking more charge 
> after it's equalized, and just keep charging up to some 
> higher potential which is what I was talking about earlier 
> in other posts. That's just not possible, or I cant see it 
> would be. Equilibrium yes, but other no.

Will,

What you imagine happens runs contrary to how the systems 
actually behave in real life.

1.) The rated dissipation is determined by the point of 
secondary emission by heat. So if we trip the grid off from 
excess current in operation is tripping when the grid is 
acting like a cathode.

2.) During an arc or anode to grid fault, the tube has 
plasma or significant leakage path inside. Opening the grid 
does not instantly make that plasma or path open. This is 
especially true when a very poor fuse like a small resistor 
is used to interrupt a few kV of voltage.

Surely you can see all that?

73,
Tom 


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