Joe, both answers are correct. True, you should never "run" the tubes
outside their specified range, but merely bringing the filaments up to
operating temperature slowly isn't running them! Also, no need to ramp the
filaments up unduly slowly. I'd say a few seconds is slow enough. You just
want to minimize the current surge caused by the low filament resistance
when the tube is cold. Once the filaments are running at their normal
voltage (5V), then I'd leave the tubes on for a few hours to getter any
residual air before applying plate voltage.
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Joe
> Sent: Sunday, November 27, 2016 07:12 AM
> To: amps@contesting.com
> Subject: Re: [Amps] SB-220 update and gettering
>
> Now I have been getting conflicting answers on initially bringing up a
pair of these 3-500Z's
> from a long rest. (almost 25 years) Some say power them up with filament
voltage only first
> and very slowly using a variac. Te others say NEVER run them at non small
window spec'd
> voltages.
>
> so what is it?
>
> Joe WB9SBD
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