You can try Marvelous Marvin,
http://www.pinrepair.comhe runs a pinball museum in South East Michigan, and if he doesn't have answers, he can probably find the people who do.
I will have to look, I bought schematics from a store on Ebay, they had hundreds for all sorts of EM machines, I'll look for the name, a schematic goes a long way to troubleshooting