I bet it is your caps on your monitor. If you know how to change the caps give it a go, if not find yourself a TV/Arcade repair guy. This process is simple and should cost you no more then $70 - 100 dollars (that would be for someone coming out to you). If you are in the Los Angeles area I can give you the name and number of a truly great repair guy, elsewhere though (unless you live in Tampa, FL) I can't really help. Best advice, call your local arcade and ask who services their machines... if they say they do, ask them who the send the board to if it is really jacked up
-Nick