According to Eimac, running the filament at 6V AC, which is 20%
higher than nominal voltage, will result in tube life which is just
1.3% of the life expectancy you could expect at 5V AC.
In other words, you lose 98.7% of the tube's life expectancy by
running at 6V AC.
In other other words, don't even think of it.
73, Alek, VK6APK
At 12:05 PM 4/09/2009, MIKE DURKIN wrote:
>So ... im wondering what life reduction would there be .. If the
>voltage was 6V-AC and alot of forced air cooling.
>
>KC7NOA
>
> > From: dezrat1242@yahoo.com
> > To: amps@contesting.com
> > Date: Thu, 3 Sep 2009 18:50:10 -0700
> > Subject: Re: [Amps] 3-500z Silly question
> >
> > ORIGINAL MESSAGE:
> >
> >
> > >> Is the filament of the 3-500z 5V-DC or 5V-AC??
> > >> The last two .PDF iv read its not stated as wich ....
> >
> > REPLY:
> >
> > This may be an old wive's tale, but I read years ago that DC
> should not be used
> > on a filament of a high power tube. The reason was that it creates a bias
> > condition where one end of the filament (in your example) would
> have a -5 volt
> > bias with respect to the other end. As a result the emission
> would be greater
> > from the negative end compared to the positive end, and the tube would age
> > unevenly.
> >
> > This of course does not apply to indirectly-heated cathodes.
> >
> > I have never seen any documentation of experiments done to prove
> the theory, but
> > it makes sense and has stuck in a back corner of my head for years.
> >
> > 73, Bill W6WRT
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
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