[Amps] 4-250A question

[Richard]

>the filiament voltage ........ for the 4-250A  tubes can you go over a 
>bit, say to 6 volts?

The emissive life of a thoriated tungsten cathode/filament varies as 
[e1/e2]^23.4.  Or, in other words, each 3% increase in fil. V over what 
is needed to produce normal emission, reduces emissive life by half.  A 
healthy 4-250A produces normal emission at c. 4.8V.  If the filament is 
operated at 6.0V, life will be reduced to [4.8/6.0]=0.8^23.4=0.0054, or 
0.54% of the normal emissive life.  (''Care and Feeding of Power Grid 
Tubes'', Eimac Co.)

>will this adversly affect the tube  what i really need to know will it 
>kill it right away.

No.  The tube should last c. 80-hours instead of the normal 15k-hours.

>What is the max filiament voltage any of you have put on this tube and 
>made it last and preform to your satisfaction?
>thanks for any help you can give
>Chris NI4L


-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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