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Title: Firing VR's in series.......an old gimmick circuit. Post by: WA4WAX on October 16, 2015, 09:00:09 AM I would use a 600V silicon piece here. See page 111. Good for VR regulator circuits in tube rigs. Probably well known to some, but worth repeating.
http://www.americanradiohistory.com/Archive-Electronics-World/60s/1960/Electronics-World-1960-09.pdf Matt Title: Re: Firing VR's in series.......an old gimmick circuit. Post by: Opcom on October 17, 2015, 12:46:36 AM Could this be expanded? AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
The original seems to allow about 3.5mA per resistor when the tube starts. If they are stacked up so that there is up to 3.5mA available to each tube before firing, might there be enough volts to fire them? I took into account basically doubling all of it. The resistor values are from the calculator for 3.5mA based on the voltages once the tubes are all lit, so don't sweat the values. instead of 47K you get 50K or 43K.. The advantage of the original circuit seems to be to fire the tubes from a lower than normally used supply voltage. It saves power and the size of the dropping resistor R1 in the original drawing. I'm trying to think through whether more than two of them can be fired off this way. No models for them.. Also, those tubes have a built in starter electrode. It's just a little rod attached to the K or A that sticks part way across the volume between the elements. It may be that with a plentiful starting voltage, less current might still result in a successful start. Thinking about 1mA.. but the original inventor probably tried that. |