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

[R L Measures]

On Jul 21, 2006, at 6:28 AM, Tom W8JI wrote:

>> 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?

I can smell it, and it's fishy.
>
> 73,
> Tom
>
>
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R L MEASURES, AG6K. 805-386-3734
r at somis.org