I use several of these that I have bought from AliExpress. There are other options from RiddledTV, but no experience with his device.
https://riddledtv.com/arcade/jamma_switchers.html
Here is what I am using them for and some notes on how it works.
- Multi Mortal Kombat (MK1, MK2, UMK3, MK4, WrestleMania)
- Multi Galaga ( Galaga, Gaplus, Galaxian, Galaga 8
- Multi Pacman (Pacman w the high score save multi, Jr Pacman, Super Pacman, PAC and Pal, Pacmania)
Generally these setups required the use of jamma extension harnesses because the space between them isn't large enough to just slip the boards in and creates mounting challenges. Most jamma extensions introduce voltage drops.
In my case since a lot of the games there aren't jamma needed jamma adapters for the boards and cabinet to jamma adapters. A lot of which I just made myself.
For MK or any games using kick harnesses you need a way to consolidate the multiple kick harnesses as they wouldn't be switched based on that design. There are kick harness condensors for various games available.
You are correct in that you have to mod them to run -5v, test and service switch, and grounds as they aren't connected through the board design.
Also by default they use a remote control, the remote is the same for every device so you can't really use more than one switcher or it will switch all of them in range. They also dont automatically select any game when you first boot up.
There is a user created device called a NoMote that is another mod (installed in those pics) that elimates the remote, allows you to select how you want to switch between games and does boot to a default slot.
Once setup i havent had any issues running them for a few years now. I made little instruction cards for family and friends to know how to switch between games.
