Roger and Carl... I'm aware of the cycling number, which is why after mulling
it over in my mind I opted to recommend the 3% drop during the idle periods as
opposed to attempting to hit the magic minimum voltage all the time...
Certainly your method works as proven by your amps... The problem I encountered
with attempting to hit the minimum filament voltage is when the power company
quietly drops the line voltage by 20 volts to save coal - and kill my expensive
tube...
A 3% decrease will double the filament life (5% will triple it)... A 3%
decrease keeps the hot oxide from passing down/up through the critical
temperature (mid 600F range) which is the major part of the loss of lifetime of
60 hours, that each off/on cycle does to a tube... A 3% swing (and even 5%
probably) will not subject the filament to undue stress, either electrical or
mechanical as there will not be an "inrush" then the voltage is raised - the
filament is still a medium orange hot and has significant resistance at a 3%
decrease...
denny / k8do
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|