[Amps] SB220 running plate current when no drive; Problem

[David Gow]

For actual Eimac tubes the Eima DATA sheet shows much greater
efficiency and usable power with 4000 volts on the plates.  Henry made
several amps with a 3200 or 4000- volt switch and  the 3KA   I had easily
made the legal limit  at 4000 volts with the original tubes after 21 years
withHenry spec. grid and plate current being carefully maintained.  He
wanted to buy new tubes and I discouraged him,  When I last heard from him
four years after the sale he was still running the Eimacs. with a new pair
of chinese tubes on the shelf gathering dust losing vacuum.
Dave W7VM

On Thu, Oct 8, 2020 at 6:27 AM Joe <nss at mwt.net> wrote:

> What is the current (pun intended) max grid current for a pair of
> 3-500Z's now days?
>
> And does it matter what the Plate voltage is?
>
> Joe WB9SBD
>
> On 10/8/2020 6:39 AM, Rob Atkinson wrote:
> > Never heard of an ICAS rating for the 3-500.  I have a dual 3-500
> > amplifier with a pair of 20 year old RF Parts 3-500s and they're still
> > at full output, but they have been run conservatively especially with
> > regard to grid current.
> >
> > 73
> > Rob
> > K5UJ
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