>
>
>> Adjusting filament-v is simpler than tuning a tank. Several models of
>> Henry Radio amplifiers use approx. 6v on 3-500Z/8008 (4.8v) filaments.
>> How safe is that, Mr Subich?
>
>
>3-500Z's have 5 volt filaments, not 4.8.
The rated filament potential is 4.75v to 5.25v. 4.8v is within the
ratings. .
> Your twisting of numbers
>reminds me of the national budget!
>
>While running proper voltage is a good idea, the number of tubes
>that fail in amateur service from loss of filament emission is
>extremely low.
So running 6v* on the filaments would actually not cause a problem in
amateur service? (* <0.6% of normal emissive life)
>The largest failure mode by far is gas ingress or
>poor welds.
>
I have seen the most failures as grid-filament shorts -- most usually
after a big-bang event. Broken welds comes in second - but this was
uniquely a problem with Eimac tubes made in Salt Lake City, UT.
>
later, Tom
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