selenium HV rectifier

[kx250rider]

I've replaced 2AV2s & 1V2s with special focus rectifier diodes, but the focus voltage goes up, and you need to be sure the control will still be in range. Same should be true if you replace a selenium with a silicon diode. If the control is out-of-range with the replacement rectifier, you might have to put a resistor in line, and by the time you do all that, it's easier to just get a new tube. Maybe not so easy to get a new selenium though. But you can use a 1 or 2 volt tube in stead of the selenium by making one full turn of wire around the iron core of the flyback, and feeding the tube filaments from it.

Charles