[AMPS] Misc. Oscillations

[measures]

>
>
>> 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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