Techno Stuff
How They Work - Start Cycle
The first start cycle of the game does a lot of things, but to get things going, we need to close the start relay. On most games, the start relay always closes whenever a coin or credit is played before the first ball is shot.
On most games, the start relay also closes when the machine is cycled for extra ball play. However, early machines may have a separate extra ball start relay that closes instead. So, let's see how to get the start relay closed.
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start circuit |
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We will assume that there are no credits on the replay register, so the initial start cycle is triggered by a coin and is shown in the green circuits. Pretty simple stuff. The coin switch is normally connecting to the circuit on the right which goes off the edge of the image (it usually powers the timer cams index and mixer latch coils). When the coin switch is pushed down, it sends the 50V to the start relay. The replay reset relay switch in the path prevents you from trying to start a game while the replay register is being reset to zero.
The two branch circuits on the right aren't too important for home use. One simply powers a meter so the operator could count the number of coins deposited in the game (or more correctly, the number of times the coin switch was closed by however a clever person did it).
The rightmost circuit is powering the coin lockout relay on the coin door. This relay is behind the coin mech, and when the coil is powered, a tab is pulled out of the mech and coins can pass through it to the coin switch. When the coin lockout coil is not powered, the tab deflects coins into the coin return chute.
On almost all games, the coin lockout coil wires are cut. In part, this is due to a really loud buzzing the relay tended to make, but it also favored the operator to disable the thing and let the machine swallow coins even if there were credits on the replay register (note that if you use a coin when there are credits on the register, the register decrements anyway!).
The timer cams index switch in the circuit to the coin lockout coil is interesting. It will prevent the game from keeping coins while the timer cams are turning. In other words, if you drop coins in quickly, the game will reject the coins until it's ready to start another cycle.
ok, but I have credits on the replay register...
Welcome to the purple circuit. When there are credits on the replay register, the replay register zero switch and anti-cheat relay direct the 50V down to the red and yellow buttons on the coin door (and blue/green/white buttons if you have those). The only interesting thing is to note that the yellow button doesn't work until the "sel lock trip relay" is tripped. Usually it's the before 5th selector lock trip relay, which means you can start playing for extra balls after you shoot the fifth ball. I guess for that name to make sense, you need to think of it as "I can/can't do X before the fifth ball is shot". In this case, it's "I can't cycle the machine for extra balls before the 5th ball is shot".tell me something useful
OK, the the most common problem in this circuit is the buttons don't do anything when you have credits on the replay register. Using a voltmeter, it's easy to check for 50V on CU switch 3A, the replay register, and the button switches on the coin door. Having said all that, the solution is most often that the connector plug pins between the cabinet and playfield need cleaning.
Want something really useful? How about how to put your machine
on free play.