Jim Thompson wrote:
On Sun, 15 Aug 2010 00:24:10 -0700, Robert Baer
wrote:

The diode across the E-B junction of Q1 was added, mostly to prevent
zenering and then beta reduction.
D1 is removed for the waveforms seen; it clamps the negative swing
seen at V3 (and the +20V supply current increases with reduced HV output).
The question is, if the voltage on C5 is changed from about +10V to
+50V, that negative swing DOES NOT change, but the positive swing of Vc
does.
Can anyone explain how and why?

Transformer polarity reversed?

...Jim Thompson
Do not think so, in any even that does not explain the "soft
clamping" (waveshape does not change) of that peak.