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Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Dr. Dark Current wrote ...
What do you think about regulating the output power of a VTTC (or a similar oscillator) with a *directly heated* tube, by changing the heater voltage?
IIRC, if heaters of oxide cathode tubes are underdriven, they tend to get destroyed quickly by ion bombardment and I suspect similar fate would await tungsten cathode tubes too at perhaps a bit slower rate, if they are devoid of their protective electron cloud.
It would also waste large amounts of power without even enabling audiomodulation or suchlike. I'd just use a tetrode instead of punishing tubes that way.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Marko, I know about the oxide cathodes which are used in indirecly heated tubes. That's why I wrote directly heated tubes, which use thoriated or carbonised tungsten filaments.
Patric, the idea of this was to decrease regulating power (less losses in the TRIAC) and to keep smooth plate voltage for the tube, so the sparks don't buzz.
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VTTC power regulation by heater voltage
