[Amps] 4-250A question

W0YR@aol.com W0YR@aol.com
Thu, 4 Jul 2002 03:06:49 EDT


You should NEVER exceed the filament voltage of a tube unless you want to 
destroy it.  There are innumerable articles about this and how some engineers 
even run filaments at slightly BELOW the rated voltage to prolong tube life.  
 Another important life-lengthener is adopting the practice of SLOWLY 
bringing up filament voltage by puting a rheostat in series with the filament 
transformer primary.  If you can't do that, at least put a thermistor in 
series to avoid excessive "inrush" current through the filament upon start up.

There is an Eimac website that has all kinds of information on this subject 
and you can find it using the Google search engine.   In any even, NEVER 
exceed the filament voltage which should be 5.0 volts!

73

Mike
WØYR