Problem with PC video to arcade monitor

[gedman]

I'm making slow but steady progress in converting a Mortal Kombat cabinet into a MAME machine.  But I've hit a problem with video.

Here's my setup:
Win7 x64 PC (Dual Core / 4GB RAM) with Ultimarc's ArcadeVGA video card (all drivers installed correctly) connected to an Ultimarc J-Pac.  The J-Pac is attached to a brand new JAMMA harness/loom (I'm not re-using the JAMMA harness that was already in the cabinet).  The JAMMA video wires are attached to a Molex-type connector which is connected to the video input of the Wells-Gardner 25" 25k7401 monitor.

When I boot the PC, everything looks fine for the BIOS loading page and then the "Microsoft Corporation" (with progress bar) message.  But as soon as Windows loads, the video gets badly messed up.  See attached image.

Any suggestions on what may be wrong?  I know the problem isn't the monitor, because it works perfectly when running the original arcade game PCB.

[mourix]

Possibly a vertical HOLD setting, but most likely your PC outputting a wrong frequency. Can you hook up a vga monitor to verify you are not outputting 31kHz?

[big10p]

Looks more like the horizontal freq/hold pot needs a tweak, to me.

[gedman]

Horizontal freq/hold was the problem.  It took a while to find the adjustment pot.  The WG 7400 monitors have all the adjustment pots on a wired remote PCB board, except for Horizontal freq/hold which is buried on the deflection board :/

Gedman