I have the schematics and I've read through a few threads here about how to read schematics, but I'm still clueless. When player 3 drains a ball, the solenoid in the backbox never seems to get power to advance for player 4 (although if I press the solenoid manually it does advance). I assume this means I likely have a broken or disconnected wire somewhere, but I have no idea what I should do to find that broken connection. I know I should probably jumper some other connection as a test, but I don't know where to begin deciding what to jumper. Any help is GREATLY appreciated.