Monitor issue - horizontal sync problem

[OldFoo]

I have a standard JAMMA cab I am running a 25" 15khz Wells Gardner U2000 monitor in and my GD ROM set up was working just fine. The old monitor chassis blew up and I was able to procure an NOS replacement which works just great with any other game I put in the cab. However, since the replacement chassis was installed my Naomi games all have some slight horizontal tearing at top of the screen, both in test mode and in game mode. It is almost non existent when I first fire up the game and then after the monitor warms up it flickers and tears periodically. I can use the horizontal hold to almost get it in sync but not quite. The chassis iteself has very few adjustement on the main board. Just 2, one for HV shutdown and one for B+, both are factory sealed and since every other game works fine, I hate to mess with those (especially since I don;t know what they do!) I tried moving the sync wire from the H- to the H+ position at the monitor and tried tying in the Vertical sync but nothing changes.



I saw another post about the Sega JAMMA I/O having a logic gate circuit that amplifies the sync signal and combines it at the I/O, has that been confirmed? Or does the Naomi output composite sync on pin 13? I have extra mobos and I/O so I switched everyhting and still have the sync issue. Maybe I should try another VGA cable? Is there a way of boosting the sync signal? Maybe I should try hooking up the mobo straight to the monitor? :smt017

[OldFoo]

Maybe I should try hooking up the mobo straight to the monitor?

If the monitor accepts a VGA signal, why not? I often connect my Naomi to a standard VGA TFT, and it works fine

[OldFoo]

It doesn't, it's a 15khz std res monitor, I would have to make an adapter.