Techno Stuff
How They Work - Ball Lifting

Almost every game has a ball lift motor. It's job is to raise a ball to the playfield when it's appropriate. Most of the games used the same circuit, so with luck, this description will cover your machine. Some later games used solid state circuitry to detect when a ball was in a playfield hole, and ball lift was sometimes inhibited until a ball either fell through the return hole, or landed in a playfield hole. Some mystic line games like Bonus 7 probably are the most complex, as this playfield detection stuff was enabled when the "special game" was being played, but disabled otherwise. Even in these games, though, the basic ball lift circuit is still there.

Probably the most critical thing in the ball lift circuit is the ball trough, so let's look at that thing first.

ball trough
surf club
ball trough

The main thing to clear up here is the numbering of the ball trough switches, and the location of the ball lifter switch.

The ball that is in the lift mechanism is sitting on the ball lifter switch. This switch tends to get cruddy, so it can stick closed. If this happens, the ball lift motor will keep running after the last ball is raised. In this case, it's the eighth ball, so you need to get all three extra balls to see the problem. The switch is just a pin pushing down on a switch blade. Either the pin is gummed up, or the blade is weak and it needs to be adjusted to provide more tension. If you need to clean this switch, make your life easy and remove the ball trough.

The trough switches are oddly numbered. Trough switch #8 is the one that has ball 8 sitting on it. However, trough switches #1-6 have balls 2-7 on them. Ball 1 is in the lift mechanism. Burn this into your memory, as the circuits make no sense otherwise.

Fortunately, no game ever needed trough switch #7, otherwise some renumbering would be needed.

Misadjusted ball trough switches will create havoc with the game play. It's actually these switches that are primarily responsible for keeping track of how many balls have been shot. Life would have been a lot simpler if the timer unit kept an accurate ball count, but that would require the timer unit to be able to step up once when a ball was shot, and step down once if a ball fell through the playfield return hole. While Bally does have a unit capable of step up/step down/reset, they either hadn't designed that unit yet, or decided not to use it.

Anyway, the timer unit will get covered elsewhere, but the use of the trough switches to keep a ball count explains why things like the "push buttons now" light can start flashing before the 3rd ball actually lands in a playfield hole (e.g. if you shoot three balls and they all fall through the return hole, the "push buttons now" light starts flashing, but you really don't need to push the buttons until three balls are actually in playfield holes ... or more correctly, four balls are out of the trough).

As a player, the nasty thing to keep in mind is that if a ball is going out the return hole, you better wait until it lands in the trough and has rolled down to close a switch before shooting the next ball, otherwise the game may lock you out of moving the numbers around before it should.

Interpreting the manual

ball trough
ball trough diagram that was never depicted in the manual

Dennis Amero provided the above image showing the trough and the description in the manual. He says the key to the whole thing is that the switch state shown in his chart applies when a ball is sitting in that position in the trough. For example, the 8th ball switch is "normally closed" when a ball is on the rollover.

Note that this is not really what Bally did on the schematic, where the switches are mostly (but, of course, not always) drawn as they would be in "game over" state. However, it is easier to see how the game works if you look at it the way dennis describes.

For example, the ball lifter switch at the bottom of the lift chute is drawn on the schematic as a normally open (N.O.) switch. The only time it's open is when a ball is being lifted or all the balls are on the playfield surface. In the chart above, dennis labels the switch as normally closed (N.C.) because it's closed when a ball is sitting at the bottom of the lift chute.

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