> ## dunno abt Indirectly heated tubes. I don't think you can drop the V
> very much ['dark heat']
> I believe, even if that's done... you still have to wait XXX minutes,
> which
> might be slightly less than
> the normal 3 mins. I believe there is a very narrow window for fil v on
> INdirectly heated tubes.
> Too low, and you contaminate the fil. Although the YC-156 has a 6 min
> warm
> up, Eimac tell's
> me to use 8 mins.
>
> later... Jim VE7RF
>
To avoid confusuon, it's the oxide cathode rather than the
fil(ament) that can suffer from too low a heater voltage in an
indirectly heated tube.
I'm not sure about the 'narrow window'. Most tubes I can think of
specify something like 10% tolerance on the heater voltage,
similar to many directly heated ones.
Steve
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