Randall AB9GO Randy wrote:
That scheme was tried in TV's and consumer radios in the 60's and 70's and called an instant on feature. The
series string filaments were run through a diode when the set was "off" and the diode shorted when
the set was turned "on". It worked as you described, but tube life was reduced due to cathode
poisoning. I wouldn't try it on such an expensive tube. If it was a workable solution someone would offer
it on an amp today as a "feature".
Some high power TV transmitting tube heaters are kept warm with
reduced current when beam Voltage is not applied with a feature called
"BLACK HEAT" (primarily during servicing hours) these klystron tubes
cost $32,000. each. Full filament Voltage is applied with bean current.
Everything else is maintained at normal levels when there is no beam
power.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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