Ulrich:
ugh! We located the root cause of the situation where nodes were getting "stuck".
It is in the pcb routing of VDD connection to the Aux winding through the rectifying diode D1 & R5 and proximity of AUX trace.
.I suspect that the via for the AUX output that is .25mm away from VDD trace in inner layers.
And that must be too adverse a shunt impedance to the VDD line. AUX coil other end is GND so it effectively shunts out charges ..do not see a short though.
If we disconnect that trace, we get back signature SWS and HVG waveforms....but is it the complete explanation?...need to explore more.
I will report more on this. An interesting lesson learnt here.
robin
