I have a JAMMA cabinet with a 25" intervideo standard resolution monitor in it.
When first powered up, the horizontal sync always needs adjusting to get a stable picture. Once adjusted, the image is fine until turned off and left for a while. Next time it's turned back on it will need adjusting again.
I've tried it with my NEOGEO, a PC/JPAC and a Pacman clone JAMMA board. It's the same on all so I'm fairly confident it's an issue with the monitor, though I can't rule out the JAMMA harness.
The monitor dates from 1992 so I was thinking of giving it a recap, but I was also wondering if the potentiometer on the adjustment board may need replacing too?
Mike