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
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