Part 1 of some thoughts/review/info on the Game King 2019-in-1 multi-game JAMMA PCB for arcade cabinets. Also, if you have a Game King but can’t get any video output from it this covers one possible cause.
One thing I misspoke about was the sub-PCB handling the video change, that is totally incorrect and I knew that before I said it. The video output is changed on the software level, so you can get 15khz video directly from the motherboard VGA out if you splice a monitor cable straight into the RBG/sync harness to your monitor. That was what I was doing prior to finishing my homemade connector cable.