Scrambled/rolling display - J-PAC, ArcadeVGA, Thomson tube

[stamps]

Hi guys!

I just picked up a sit-down 2player cab for cheap, and replaced the dodgy Chinese PC inside.
The new PC has an ArcadeVGA 3000 and is interfaced to the cabinet via JAMMA with a J-PAC.

My problem: I can't output any video that the monitor will display.  Everything is scrambled/rolls like I've got the wrong resolution or refresh rate.

• ArcadeVGA 3000 and J-PAC
• ArcadeVGA drivers installed, 640x480 chosen in quickres utility
• Rolling/scrambled screen all the way from POST into Windows (Windows 7 64bit)
• Tested output to an LCD monitor via the ArcadeVGA DVI connection: OK.
• Tried all combinations of jumpers on J-PAC: 15Khz+31KHz and 25KHz-only (also tried removing all jumpers for the composite sync.)
• The self-test LED on the J-PAC is lit solid.

Here's the only info I can see on the back of the monitor:
 

Code: [Select]

  Thomson A68EMN021X0A1
  D-RNJD0399 [00]
  93701CSMCZ
  59241092386
  09/13/09
(The monitor works with the original PC in it, so the display itself doesn't seem to be faulty.)

Is anyone able to illuminate me?  Thanks heaps!

[MonkeyJug]

hi mate,

i'm no expert, but have you tried running the vga straight to the video card (bypassing the j-pac altogether)?

[stamps]

have you tried running the vga straight to the video card (bypassing the j-pac altogether)?

Hey MonkeyJug,

Good idea.  I haven't tried that yet.  But my understanding of the J-PAC is that it doesn't modify the video signal at all, it just passes-through - but only if the signal is 15 or 25KHz (depending on jumper setting.)  I'll give the direct connection a go when I get home!

[gavincoolguy]

I'm no expert but did you at least adjust the horizontal and vertical sync after changing everything out ?

[stamps]

I'm no expert but did you at least adjust the horizontal and vertical sync after changing everything out ?

You may not be an expert, but I'm definitely an idiot. 

I had no idea there was a dozen potentiometers on the monitor board to adjust the picture.  The H and V-sync was off so badly that I didn't even think about it.
Fixed! Thanks everyone for your patience 

[gavincoolguy]

Woo glad I was able to help, only been actively participating in this hobby for 2 months or so.