Most games from this era won't start if you don't have all the balls in the trough. as for switches instead of optos. Optos work opposite of mechanical switches. That is, they are "closed" when there's no ball present, which is the opposite of a mechanical switch. But you can wire the switches in reverse to compensate for that. I've never done what this guy did, so i can't comment any further. But i would go into switch test and make sure the 3 ball trough switches are working. And maybe ask the guy if the game ever worked...