[Hallicrafters] High line voltage

[Roger K8RI]

> Regardless of the specification for the radio, running high filament 
> voltage is without question, one of primary ways to prematurely kill a 
> tube. The other is forcing the tube to run hotter.
>
> There's no rocket science and no debate...running high filament voltage 
> WILL reduce your tube lifetime.
>
> Do I care on a 6AU6...probably not, but I sure do on my 3-500Zs and 572Bs.

"It seems" as if I remember reading that you don't want low voltage either 
when it comes to power tubes.  If the filaments are straight tungsten, they 
are very forgiving, but thorated and indirectly heated coated cathodes are 
not.  OTOH, you can sometimes bring weak tubes back to life with a couple of 
minutes of raising the filamanet about 10%.  If they are already weak there 
isn't much to lose and everything to gain.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com

>
> John K5MO
>
>
>
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