[Amps] DC On tube filaments

[wl fuqua]

The only problem that I can see (and this effect should be small) is that 
the more negative end of the filament of a directly heated cathode would 
emit less current than the positive. In some cases like a 250th one end of 
the cathode is at the top and the other is at the bottom. So one end of the 
plate would dissipate more current than the other.  In the case of say a 
304tl or th  one pair of plate would have slightly more current than the 
other. But I expect that a few volts difference would not cause much of a 
problem.

73
Bill wa4lav



At 08:42 AM 10/9/02 -0700, Randall DuCharme wrote:
>Greetings,
>
>I'm told by an old Army radio operator that they used
>to periodically reverse the filament polarity on a
>transmitter ( the exact nomenclature escapes me at the
>moment ) that used an 813 and a DC filament supply, to
>extend the filament life.  I have no first hand
>experience with this myself but have been tempted to
>try it.
>
>
>
>--- MorgusMagnificen@aol.com wrote:
> > Those who are opposed to DC on filaments should
> > immediately notify the
> > Department of Defense, as they have apparantly being
> > erroneously doing this
> > in all of that aircraft electronics since the days
> > of the Wright Bros.
> > (almost).
> >
> >        Remember the 1625? It was an 807 with a
> > specially re-designed filament
> > to run on 12VDC, with two of them (wired in series)
> > in the ARC-5 TX's powered
> > directly from 24VDC.
> >
> > Eric von Valtier K8LV
> >
> >
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>
>
>=====
>Microsoft is not the answer.
>Microsoft is the question.... and the answer is NO!
>
>Randy  (AD5GB)
>
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