So I picked up a barn fresh EM today. It appears that at some point it had a critter or two living in the cabinet. The relay board in the bottom of the game is considerably dirty from whatever was living in it plus the regular old pinball dust and dirt. I want to clean it up but compressed air and a brush does not seem to be doing enough. I think I need to go to the next level. I had an idea of filling a spray bottle with alcohol and spraying sections at a time while soaking up the dirty run off with a rag or something. I would let it dry out for a few days in the sun after this. Or, I seem to remember seeing a video of someone simple greening and washing the board down with a garden hose and water. I was wondering if anyone in here has tried either of these methods or has one of their own they could suggest. Any opinion much appreciated.

Thanks for the advice people!

Wizardblom - thanks for the link to the video. I knew I had seen that before but I couldn't find it in my search.

I tried the 91% alcohol in a spray bottle this weekend. I sprayed down a section and used a paint brush to rub loose any dirt. Then spray it down some more and blow it clean with compressed air. That seemed to clean it up a bunch. I don't think I'll try the simple green and water method this time. I will however replace the bottom board that the switches are mounted to as newmantjn suggest. It should help get rid of the wet musty smell I imagine. It's already looking better than when I found it! Thanks again everyone.