VGA port doesn't work when connected to J-pac but DVI port does

[xga]

Hi Guys.  I have an old perfectly working Groovymame setup with a ATI HD 4350 video card running on a Windows XP64 PC that I have pulled out of a cabinet with a tri-sync monitor connected by a VGA cable.  I want to get this running in a cabinet with a Nanao MS9-29 monitor using a J-pac for video and have made the required changes with VMMaker.  The 4350 video card has a DVI and a VGA output however, I get no signal to the MS9-29 monitor out of the VGA port when connected to the J-pac, but it works when I use a DVI to VGA adaptor from the DVI port.  The VGA output of the 4350 works when connected to VGA LCD monitor that accepts 15kHz, so it seems that the J-pac doesn't like the sync coming out of the VGA port for some reason (SYNC IN lights up amber, but SYNC OK doesn't on the J-pac board).

Is there a simple way that I can get it to work via the VGA output of the 4350 video card and not have to use a DVI to VGA adaptor on the DVI port?

Thanks in advance.

[Calamity]

Hi xga,

That's not JPAC's fault but your video card not detecting the arcade monitor. Probably your tri-sync did load the RGB lines with 75 Ohm, but the MS9-29 doesn't. The easiest method is what you're already doing: DVI->VGA. The DVI works because although it doesn't detect the monitor either, it's the default output so the video is routed through it. Other solution to actually trigger detection is to add resistors between the RGB lines and earth (75 Ohm value is recommended in many places, but in my experience it produces a very dim picture; 270 Ohm still works and doesn't cause a visible brightness drop). Finally, Windows 7 Emudriver is patched to force detection.

[fuchi_jeg]

Try a different vga cable. Some cables carry a connection on pin 9 (I believe pin 9) that supplies +5 throug the pin. Other vga cables are missing this connection. In my experience  the voltage will cause the monitor to go out of sync.