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[Amps] 3-500Z plate durability

To: amps@contesting.com
Subject: [Amps] 3-500Z plate durability
From: jsb@digistar.com
Reply-to: jsb@digistar.com
Date: Tue, 9 Dec 2003 10:15:43 -0500 (EST)
List-post: <mailto:amps@contesting.com>
We got a good rousing set of replies on how to wire 220V, maybe we can
strike gold again on this one...


3-500Z plates - I'm reading that they "enjoy" getting dull red hot.

My first ham gear was a Drake T4XB and R4C B-line and I distinctly
remember being warned by my grandfather that the best way to ruin 6JB6
tubes was to let them even slightly get red - because at that point they
were essentially worthless for very much output.

So what prevents 3-500Z or 3-500ZG tubes from failing prematurely when
used in the manner i've been reading about, running them dull cherry red?

I read that the heat generated by the kinetic energy of electrons hitting
the plates is what creates the heat (not the plate current), and this heat
"activates" the zirconium getter but what prevents the plate from dying
like the old sweep tubes?


Do 3-500Z tubes get "soft" or do they just suddenly drop output and fail?
And do they fail because of high grid current causing the grid to warp and
short or because of some other reason?



regards,
Jason N1SU
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