No vertical sync
Check Pin #9 signal level and timing
of connector
Normal
Check Verticalty of CRT Display
Adjust Vertical hold
No vertical sync
Check Pin #1 signal level of IC31
Normal
Trouble in IC31 (IC31 Replace)
Abnormal
Abnormal
-34-
Trouble in logic
M-900 X X X Series
M-1200 X X X Series
Trouble in Q17 or R301, C302, C303