~ 5000VAC should light the tube TO A VERY FAINT GLOW, its better for the health of your PSU if you have a kilo-ohm or so ballast in series with the tube.
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OK to connect to big HENE supply IF and ONLY IF you have 47,000 Ohm (47K0, aka 47K) one to three watt ballast resistance in series with the tube.
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Once the ion tube lights on such a small current the voltage across the tube will probably drop to less then 500 volts,actually probably about 200 VDC..
Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...