Here is one thing to try. With your machine on and door closed, open your belly glass door and with the help from a small mirror, look inside to see if your comparitors LED light is. It will only light with the door closed. Have you tried a different wiring harness for the coin comparitor and coin optics to the door plug or check the door plug for a bend pin or one pushed out of the plug? Have you verified that you have a good comparitor? There is a capasitor that goes bad on the board inside those units.