I'd have to look at the schematic but you can set the balls at start on some of these game, ie 5 6 7 balls at start. no need to have control in the 1 2 3 range. Of course when you hit zero balls there is a limit switch to kill function, look at the back side of the stepper. And most likely a missing tooth to prevent more than 10 or another limit switch...

Does not apply in any way to "King of Diamonds". Only five balls to play each game. Count up stepper, with a reset coil to return it to home position at the start of the game.
"Solitaire" and "Hit A Card" are probably different as well. Extra balls won are shown as diamonds on the backglass.
Not sure, but they probably have a separate stepper for extra balls, since the initial five balls are displayed on the card tray, a la "KOD".

On this era of Gottlieb AAB games, during reset the ball count unit is first counted down to zero, and then counted back up to the appropriate "balls to play" position. When the ball count unit gets up to the correct number of balls to play, the control bank reset coil fires, which completes the reset cycle.

There is a switch on the "add" drive arm of the ball count unit that closes when the drive arm has pulled in far enough to advance the ball count unit to the next position (typically called an end-of-stroke or EOS switch). The control bank reset coil is wired in series through this switch and the rivets on the ball count unit that you are asking about. During reset, when the ball count unit has stepped up to 4, the circuit to the bank reset coil is enabled by the rivet at position 4, but the EOS switch on the ball count unit is open, so the bank reset coil does not fire at this point. This occurs because the disc on the ball count unit does not move at all when the add drive arm pulls in; it only advances to the next step as the drive arm returns. When the drive arm pulls in while the ball count unit is already sitting at position 4, the EOS switch on the drive arm closes, and now the control bank reset coil fires. This takes the game out of reset at the same time that the ball count drive arm returns, advancing the unit to 5 balls to play.

So while it may seem a bit odd that the ball count unit rivets enable the control bank reset coil one position too early, it's actually correct. The additional rivets are there as a safety factor, in case the control bank doesn't quite get reset at the step from ball 4 to ball 5. This should never happen on a properly functioning machine, but if it does, the rivets at all the positions above 4 keep the circuit to the control bank reset coil enabled. Otherwise, if there was a glitch at position 4, the ball count unit would run up to 10 balls to play, and the machine would be permanently stuck in reset because the control bank reset coil would never fire.

On machines with an adjustable starting balls-to-play (3, 5, or 8), the adjustment plug position controls whether the rivet at position 2, 4, or 7 is the first one that enables the control bank reset coil circuit.

- TimMe

Yes, 100% correct. If you don't have rivets at positions 2 and 3, or any connctions to rivet 7, then your game can only be set for 5 balls-to-play per the factory wiring.

However, Gottlieb may have included the additional rivets on Diamond Jack to allow the operator to do a field modification to make the game start at a higher balls-to-play setting. This is just a guess on my part, but that would be something they might do.

Connecting all of the rivets, and providing the option to start at 3, 5, or 8 balls-to-play, was done by the factory on slightly later AAB games. For example, the schematics for Card Trix (1970) and Astro (1971) both show this.

- TimMe