I was going for another phase shift oscillator, but then this happened. Kilovolt spikes are inevitablewhen suddenly cutting off current from a 10 Henry transformer primary. Years later, I turned it into a little high-voltage DC-DC converter. 5W in, 3.46W out; 69% efficiency.
The capacitor near the transformer does not appear to be a resonant component, it merely stabilizes it.
Transistor should handle:
Vc: -300V +2.4kV
Vb: -300V +1.81V
Ib: +340mA (spike only)
Ic: -710mA +900mA (- is spike only)
Ie: -340mA +910mA
