I have a complete Mystic Marathon and a partial kit with the 2 main boards that are now giving me graphic issues.

The chassis has been rebuilt but I haven't had time to adjust it.

I'm not sure if both just developed issues or if it's something else. When I hit the test button it cycles with garbled graphics.

I'm good at installing things but I'm useless repairing. I can switch socketed chips since i have two sets if it seems obvious what my issue is. There are other things I could replace but I'm hoping someone can point me in the right direction.

Any suggestions would be fantastic!