[ARC5] Filaments - How Low Can You Go?

[J. Forster]

If filaments are operated significantly below their design temperature,
the emission will fall, and I don't mean in a simple, reversible manner.

Filaments rely on replenishment of the surface from deep within the body
of the material. This is a temperature dependant, solid diffusion process.
If the body is operated at too low a temperature, the surface will not be
replenished.

If you're worried about the filament burning out, operate the thing at
maybe 10% below design voltage. Lifetime is a power law of applied
voltage. That should lengthen the life a lot, but still maintain emission.

-John

=================



> Here is a stupid question for y'all.
>
> Considering that the overall recommendation is to operate the command
> receivers with reduced B+, just how low can you go on the voltage for the
> filaments before you have a problem?
>
> With say, 125V B+ and 12V filament power with a command receiver that has
> 12V tubes and wired for 24V, how well will it work?
>
> In experiments with my first command set, an R-11A, I was astonished that
> I could get the B+ down to around 28V and it was still working, if rather
> faint on the audio output.
>
> Thanks!
>
> Wayne
> WB5WSV
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