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Re: OLD Tubes/Coils - filament power (fwd)
---------- Forwarded message ----------
Date: Mon, 3 Mar 1997 18:16:01 -0500
From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: OLD Tubes/Coils - filament power (fwd)
> Date: Sun, 2 Mar 1997 22:29:49 -0700 (MST)
> To: tesla-at-pupman-dot-com
> Subject: Re: OLD Tubes/Coils - filament power (fwd)
> From: Tesla List <tesla-at-pupman-dot-com>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 02 Mar 1997 16:59:06 -0800
> From: David Trimmell <dwt-at-efn-dot-org>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: OLD Tubes/Coils - filament power
>
> Hello,
>
> > *Never* operate tubes (at least those with thoriated heaters) with
> >less than their rated voltages and currents. Doing so will strip the
> >cathodes in short order. You may get lots of filament life with near
> >zero emission. Standard incandescent Light bulbs are a different story
>
> >entirely. The warning also applies to halogenated bulbs which will
> >have their lives shortened since the chemical processes in them rely
> >on running their at the high temperatures as far as I am aware.
>
> >Malcolm
>
> I was wondering if anyone knew if the 803's use a thoriated filament? I
> am using two 803's in parallel, with several turns on top of the primary
> of the microwave transformer to get about 9.5 volts to power the
> filaments, since this arangement isn't curent limited, am I in danger of
> damaging these filaments?
> Thanks,
>
> David Trimmell
David,
The 803 IS a thoriated tungsten filament tube. Rated filament power
is 10 volts (AC or DC) at 5 amps. They have a plate dissipation
rating of 125 watts and a rated anode rating of 2000 volts. I'd say
you are quite safe employing a pair of these on a single microwave
transformer as long as you do not exceed control grid current given
as 50 mA in the RCA tube manual. If your filament power is coming
also from the microwave transformer that is supplying the plate
voltage, do not 'throttle' this transformer with a variac for power
control.
Have fun.
rwstephens