Here's some good reading on Bally mid-70's EM start-up sequence from Clay's guide while you're waiting.
Starting in the early 1970's, "operation manuals" became available from EM game manufacturers. These manuals outline a "start-up sequence". This is the sequence of events that happens after you press the game's start button. If your EM game doesn't start up properly, this sequence of events can help determine the problem.
The start-up sequence is game specific, but generally can be applied to most games. This is helpful especially on older EM's where there is no operation manual.
The following start-up sequences were outlined from mid-1970's games. They may not apply to the game you're fixing. But they will give you a general idea of what an EM game does when you press the start button.
Bally Start-Up Sequence.
Coin is inserted into the game. The coin relay will energize. It will stay energized through its own hold-in switch and a score motor switch. If the credit button is pressed (instead of a coin being inserted) and there are credits, the credit relay will be energized which energizes the coin relay.
The coin relay will energize the lock relay (this turns the general illumination on). The lock relay will stay energized through its own hold-in switch and a delay relay switch.
The coin relay will energize the reset relay, through a game over relay switch (if your game won't start, try cleaning the contacts on the game over relay; a very common Bally problem).
The score motor will operate. This will energize the score reset relay(s). The score reset relay(s) will attempt to clear the score reels to zero. This is done by operating the score motor. Each turn of the score motor will operate the reset relay once, which in turns moves a score reel one position, until the score reel(s) are at zero. If the score motor continues to run when a game is started, there's a good chance the zero position switch on the score reel(s) is dirty or mis-adjusted.
The coin relay, through the score motor, will advance the total play meter.
The reset relay, through the score motor, will reset the stepper units (zero the ball count and player units).
The coin relay, through the score motor, will decrement the credit unit.
The coin relay, through the score motor, will energize the game over latch relay coil.
The coin relay, through the score motor, will energize the 100,000 relay latch coil(s) (if the game supports scores greater than 99,999).
If the outhole switch is closed (single ball games) or the ball trough switches are closed (multi-ball games), a ball is released to the shooter lane through the outhole relay (single ball game) or ball release relay (multi-ball game) and the score motor.
On multi-player games, the credit button may be pushed again to add a player. This time the coin relay will not energize the reset relay. Instead it will (through the score motor) advance the total play meter, decrement the credit unit, and advance the coin unit.
More Bally Start-Up Sequence Info.
Taking the Bally sequence a step further, here is the sequence for a common multi-player game like Captain Fantastic.
Coin inserted into game closing 1st coin switch. The coin relay will pull in.
Next the reset relay pulls in. The reset relay will stay energized until all score reel zero position switches are open (signifying all the score reels have reset to "zero".) On a four player game there are 16 of these switches hooked in parallel.
In the backbox there are two score reset relay which pulse, due to switches on the score motor. As these pulse they energize the non-zero score reel coils, getting all the score reels to the zero position. This is handled through the score motor 2A and 1C switches, which pulse the two score reset relays.
On the reset relay switches will reset the player unit (in the backbox) and the ball count unit (on the bottom board), and the game over latch relay (taking the game out of "game over" mode.)
If the bonus stepper unit (mounted under the playfield) is not at reset position, the Bonus Score reley will energize. Using score motor switch 2B and the bonus unit reset coil, the bonus unit should get to the zero position until a switch on the bonus unit opens.
With the score reels and bonus stepper reset, the Reset relay should de-energize and the score motor should stop.
Now the ball, which should be in the outhole (closing the outhole switch), should pull in the outhole relay. This will again start up the score motor, using a switch on the motor and the outhole relay to kicks the ball to the shooter lane. The outhole relay will also increment the ball count unit if the Ball Index relay is energized. (As soon as a point is scored, the ball index relay energizes.) This is no different than a ball drain during game play.