[Amps] 3-500Z plate durability

[carl seyersdahl]

I don't know about the 3-500 , but I think it depends on the tube type.!!
When I was in signal school, (many years ago, 1948) we were taught how to
tune and load a hi-power amp using the color of the "plate" (bright red) to
determine proper load. .. !! A little crude , maybe but that's how it was
done back then. !! Today, I don't know.!!! If it got near white, look out
.!!!!!
    carl / kz5ca    (memories)
----- Original Message ----- 
From: <jsb at digistar.com>
To: <amps at contesting.com>
Sent: Tuesday, December 09, 2003 10:15 AM
Subject: [Amps] 3-500Z plate durability


>
> 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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