Hi All,
I'm relatively new at this and have an older 1966 Williams 1 player EM that has been playing perfectly for months. Until now that is. When I plug the machine in and hit the start button the lights come on and the game hums a bit. It will not reset score reels and begin a game. If I manually activate the reset relay and outhole relay it will reset and begin a game. The game will play perfectly including kicking out balls, adding balls etc. but when the game ends on the last ball and the "game over" light comes on it will not begin another game by hitting the start button. You have to manually activate the reset relay again. Same thing if you tilt the game. If you hit the start button it will do nothing but hum.
I should add that the coin mechs have been removed and a start button was installed on the front. Any idea's?

Thanks for the suggestions, the reset relay was engaging but not making contact. A little emery cloth and cleaning and she's back up and running.