C-2154 PCB repaired

We checked the Pulse modulation PC Board and replaced the Zener diode D9 and capacitor C1. Then I put back the board to test the system, unfortunately the system could not run in the right condition. I could not adjust the high voltage yet. When I monitored the frequency input Vref, I found there was only a noise signal. The reason of this may be the extend board or the signal from Control Rack R03.