>
>> to the rear of the amplifier. I know I have seen that tubes like
>> the 3-500 can get extended life by lowering the 5.1v filament
>> voltage to something slightly lower. Does this also apply to the
>> 4CX800 and similar tubes? I think the specs on the 4CX800
>> are 12.6v +- .7 volts.
>
>In amateur service, virtually zero tube failures come from filament
>hours.
// ... depends on filament potential. The three Henry Radio models of
3-500Z amplifiers that run 5.8 - 6 v on the 5.25v-max. filament typically
have a useful emission life of a few hundred hours.
> Most come from excessive grid currents or just plain old
>flawed tubes.
>
// Are all of the reported 8877 failures in the AL-1500 due to a
manufacturing flaw at Eimac that lasted for 14-months c. 12-years ago?
>With an indirectly heated tube, you can actually ruin the tubes
>emission by operating at low voltage. Gettering is also on the
>cathode, and may not work correctly if heater temperature is too
>low.
>
>Run the tube dead on the rated voltage,
// Operating a filament or heater "dead on" seems to contradict the tube
manufacturers' ratings of +/- 5%.
> ...
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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