First Unplug the machine right now before you fry something or make the machine worse without doing some pre tests.
Now go to these two websites and read on how to proceed in diagnosing and fixing that machine. This will save you time and money.
http://www.pinwiki.com/wiki/index.php?title=Bally/Stern
http://techniek.flipperwinkel.nl/ballyss/rep/index1.htm
If you get stuck post back.
Mike