Sharp SX76NF200 Service Manual page 12

TROUBLE SHOOTING FLOWCHART
NO VERTICAL SCAN
Check the Voltage at pin(15)(1)
of IC502
Check D613, D615,
R647 and R646
Normal approx. 14V
Check vertical trigger pulse at
pin(12)(13) of IC502
Check IC4003 and
peripheral parts
Check IC502 and related circuits