I have a Bally 1978 Kiss pinball machine which I have owned for twenty years and outside of a few minor issues the machine has been pretty reliable. Recently though it will not play at all. What I mean is when the machine is turned on the led on the main MPU flashes 7 times and the machine completes it's boot up process. But when you push the silver button on the front of the unit to put a ball in play, nothing. When you open the coin slot door and push the test button, and cycle the unit through the various test modes, everything seems fine and it goes through the test process with no issues. All the lights come on, and all the solenoids and flippers work. During the test mode it does eject the ball to put it in play, but not during the normal playing process. The one thing I did notice during the boot up process is the start up tune is noticeable different and distorted to a degree. Any assistance would be much appreciated.