fixed the display simply by switching the monitor form negative to positive sync. there is a toggle switch on the chassis pcb
set dips switches so game in free play mode.
test played and number of minor issues appear:
1. loose ground connection in the control panel wiring - sometimes buttons suddenly stop working. wriggling the molex connectors can get it working again.
2. constant beeping when coin door harness connected. need to double check wiring hack/soldering. disconnected coindoor temporarily - not a problem as in freeplay mode.
3. vertical movement of the trackball is reversed - simply resolved by crossing over yellow/green wires on the trackball harness wiring.
4. volume pot does not seem to make any affect on the volume