I have a Virtua Cop that when tuned on after the game boots up. You can hear it palying so the power supply and the PCB should be ok. Could it be that the flyback is going out?
Check power to the monitor. See if you have neck glow with the game turned on. If not:
Check the monitor fuse.
Inspect the flyback for obvious cracks / holes.
Discharge the monitor, remove and re-flow the chassis. Re-flow any connector. If the monitor is old, put in a cap kit and a new fly.
Reassemble and test.