HP8560A display problem

[thlee]

I brought a second hand HP8560A but there were display problems after power on. The displayed characters were incomplete as shown in Figure 1. I had replaced U207 in A2 control board , trying to fix it.  Unfortunately, the problem cannot be fixed. Two resistors R250 (3.16M) and R251 (1.1M) were checked and they were ok.
   
I execute the CRT adjust pattern as shown in Figure 2. All @s and some characters were not displayed fully. Two segments from the upper right corner to lower left corner were dim except at the starting points.

Anyone can advice me how to fix it?

[thlee]

I have captured line generator output waveform as shown in Figure3 . The figure3a and figure3b are zoomed in waveform. Two signals (z out and blanking) are different from service manual as shown in Figure4 but I am not sure. Anybody can suggest me what is a problem?