First, in the test menu go to clear all balls. Two should be loaded in to the cannons, one should pop out on the left ramp, then the other three should launch from the trough.
After you have emptied all balls out of the machine, load all six into the trough. Exit back to the game. try to start a game, the machine should load three balls in the the subway. if that is not happening then you probably have a bad ball trough. You can get replacement sets from Great lakes modular, they are great and no too expensive.
If the balls load correctly and your problem persists you may have a flaky opto in the subway.
Quoted from forensicd:Well, when i luanch the probe at first, the little blocker doesnt go downs sometimes, or perhaps when I hit lock as well from launch. Suppose it is a dirty switch perhaps. Them main issue is that during multiball, it seems only one ball is available, nothing else is coming out of the trough. The game is then endless, it just keeps kicking out the same ball over and over after it drains.
If the drop target is not working correctly you will have problems on ball launch, you will not be able to collect any of the SKILL shots on ball launch, and locking a ball during gameplay will be a problem as well. Go over the drop target assembly. make sure the coil is not fried, the drop spring, the long one that pulls the drop down when it is hit, is not worn out. basically just make sure all the parts are not worn out or bent.