JAMMA Arcade Monitor jitter after 1 hour

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: Hi folks, : I get a great picture with my 29" Hitachi arcade monitor....for about an hour. After that, the picture tends to jitter vertically a little. It's still playable but can be very annoying. I played with the vertical and horizontal hold but it still does it, but not when it's first turned on. The picture doesn't roll. : I am using ArcadeOS and the basic MAME release version 0.36 on a PIII-450 with a Creative Labs 3D Blaster TNT2 Ultra video card. : I interface the video through a JAMMA fingerboard and a hacked VGA cable. The JAMMA connector only has composite sync so I twisted the V.sync and H.sync leads together and soldered them to the fingerboard. : I saw an XOR gate mentioned on a JAMMA conversion site somewhere, maybe it was Brian Lewis' site. The site mentioned that combining the H.sync and V.sync wires together to form the composite sync worked for him but technically a XOR gate should have been used. Anyone care to tell me what this is and if it could cure my problem? As you can tell, I'm not an EE! : I am assuming my problem is something to do with sync issues. Am I assuming correctly? What else could it be? : At first I thought maybe it was a loose connection somewhere but how come the picture is fine for about an hour, that's the part that confuses me. Is it possible that I have a loose solder connection somewhere on the monitor pcb that once the joint heats up, the crack expands causing a loose connection?...or am I really stretching? : I may need to buy a JAMMA pcb (I had one but sold it too soon!!) to see if the problem exists on a "real arcade game". : Any suggestions would be appreciated. : -Tom A.

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