Techno Stuff
How They Work - Extra Balls

Most games have a yellow button on the front door which is active after the fourth or fifth ball is shot and let's you play for up to three extra balls.

Generally, these extra balls are awarded randomly, and as you might expect, the higher your scores/features, the harder it is to get an extra ball. In addition, each extra ball is harder to get than the previous one.

A few games which were designed to remove the gambling gave guaranteed extra balls, and some games gave the first extra ball as an award for landing in the "ballyhole", which was usually hole #16 when the ballyhole feature was lit.

We'll be looking at the most common extra ball mode, which is the random awarding of extra balls during yellow button play. The extra balls are controlled by the extra ball stepper unit, and this thing has three primary functions:

1. light the extra ball lights on the backglass
2. enable raising balls to the playfield, which is discussed in the ball lifting section.
3. stepping itself up to higher positions

surf club
extra ball disc diagram - click for big version

Before we look at the functions of the extra ball unit, let me toss out the most common problem you will have during extra ball play - when you push the yellow button, the game resets.

On most games, pushing the yellow button flops the game into extra ball mode (extra ball trip relays trip) and the start relay is closed to cycle the game. If the start relay closes before the extra ball trip relays trip, then the game acts like the red button was pushed instead. You'll need to adjust the switches behind the yellow button so the extra ball trip relay switch closes as soon as possible, and the start relay switch closes as late as possible.

Surf Club is not a good example based on the above description, as it is one of the earlier designs that has a separate extra ball start relay and extra ball play relay. However, a similar issue exists in that the extra ball start relay must close late and the extra ball play relay and trip relays must close early otherwise a game reset will happen, so the adjustment of the yellow button switches still matters.