Pulse Modulation Control PCB

I already replaced the SCR on high voltage power supply board M03, also checked the high voltage diode rectifier SCH20000 yesterday. But I could not tune the voltage later, I found there was not correct output at the Firing Angle at pulse modulation control PCB. That trigger pulse voltage was less than 1 V.

Mike helped me to check the board. We measured the pulses on pin 1 at A4, pin 7 at A4, pin 6 at A1 and pin 6 at A2. We found it's feedback to decrease the voltage of Q1 input.