Im having an issue with a williams system 9 mpu (comet) booting the led display on the board shows 0 as if the board booted properly but the game is dead as a post no displays no attract ect. I thought maybe a faulty 6116 but have tried nvram as well as std ram with no change. Tried cycling adjustment switches on coin door no change. All boards have been gone through voltages are within spec and clean. Board was also tested in another comet with the same results. Any ideas