this is the approximate schematic, reversed from pcb. I don't have anything else.
in the red rectangles are the measured values on the bad power supply.
the vcc is oscillating between 8 and 12 volts.
there should be 10-20V on the pfc controller Vcc, but a fixed value. from reference designs there should be 17V dc.
I presume the (zener?) diode is bad ?
what do you think ?