Well, since I seem to have started the last round, let's see what I can do
here...
It's normal for these types of tubes for their plates to turn cherry red. They
are run 24/7 like
that in the broadcast industry, and replace them when they show a little age.
They can and have
been used successfully in amateur gear as "pulls" for years following.
In my amp, when I transmit (espeically in the typical long-winded 350W carrier
AM transmission),
my RF Parts 3-500ZGs get quite red (almost orange). After 1 year of pretty
consistent use
(abuse??) like this, they still run full output.
I think the BIG difference between these and the sweep-tubes you reference it
is that they're just
not transmitter tubes and aren't built handle it.
How'd I do, fellas??? :-)
Joe,
N3JI
--- jsb@digistar.com wrote:
>
> 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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