https://www.arcade-museum.com/manuals-arcade/Main%20Schematic.pdf
https://www.arcade-museum.com/manuals-arcade/Sea%20Raider%20Instructions.pdf
https://www.arcade-museum.com/manuals-arcade/Sea%20Raider%20Schematic%20%20Sound%20Board%20.pdf
Maybe documents on Klov can help you. I would take a look at the gun itself. Does it have a way to calibrate home slot? Do the gears look good not chipped or missing teeth? Cool shooter game!