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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