Response from Jonathan: George,

Sounds like you are experiencing a monitor collapse issue. This can be caused by a bad vertical hold adjustment on the remote board for the monitor. If that’s good, check out resistors R167 and R177, capacitors C137, C142 and C144, as well as chips IC103 and IC104 to make sure all these parts are working properly. Please see our post on Repairing Monitor Collapse Issues for additional information on this issue. Hope that helps.