Check to see if you are getting the 120 volts AC power at the monitor's power input connector. If no power there then you've got a problem in the game cabinet like a blown fuse, a bad isolation transformer, broken/disconnected wire, bad connector, etc.
You should install a capkit. There are several electrolytics located around the power regulator transistor and the yoke connectors that go bad. These will prevent the monitor from powering up.
Check C606 (47 uf @ 50 volts) as it's probably open.
Check C501 (10 uf @ 250 volts) also probably open or way off value.
I looked thru my service manuals and you definitely have the Kortek chassis that was sold by Sharp Image around 1988.