Re the smart bleeder.
Cascode two or more HV Power Fet modules, Drain to Source etc, and use
resistors to set the individual gate voltages for the upper FET's so they
(more or less) share the load. Top most resistor to the top most FET
Drain.. Then the lower end of the lowest resistor to Negative (the
Source of the lower "controled" FET) Then, taps in the chain, to set
the gate voltage of the middle and top FET, spreading the applied voltage
across them more or less evenly. Even FET's have safe operating areas,
not as square as you might like either, when the disipation limit line
intersects the graph.
Or.. SSR in/out series resistors in the transformer primary, much like
the "Step Start" scheme, to prevent the unloaded HV from wandering up too
much. In conjunciton with a low disipation bleader.
Or.. A regulated HT supply, much like the G4FRX (I think) design a while
back. (Phase controled Thyristors in the primary, I can't find the
article at the moment) Should be easier now perhaps, with more modern
and capable power semiconductors.
QRM from the Thyristors shouldn't be much of a problem, as you're not
receiving when you're "using" them. Good filters on the AC input
though, with short wires to the transfomer, and the whole HT supply in a
Then you can dial up whatever volts you want, and they'll be stable with
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