[• 5 v2 Instructions / FAQ]

• 5 v2 Instructions / FAQ
• 3.x Instructions / FAQ
• RaspJAMMA Mini Manual
• RaspJAMMA 4-P Manual
• Mac Partitioning Guide
• Dipswitch Guide
• RaspJAMMA PCB Layout
• How to Fit your Raspberry Pi
• GPIO Wiring Guide
• Compatible ROMS List

I did it in widescreen, but for some reason it uploaded it in vertical.

I don't see any video (?), but the LED on the monitor makes me think it could be a modern monitor?  If so you likely need to set the software to highres in config.txt

EDIT: looks like a new post with vid has appeared...

set high res in config.txt AND remove the DAC from the RaspberryJAMMA board (lleave the HDMI end in plugged into the Pi) and plug your monitors VGA cable into the DAC directly.  Should have it all up and running.