The Corvette Prototypes

In Ask Uncle Willy #15, Uncle Willy told the story of how the original design for the Corvette pinball machine had included drop targets and a gear shifter. Uncle Willy finally had the chance to take pictures of the only machine believed to exist with these parts, and will now share those pictures with you, along with the details of how the drop targets were wired into the game. (Uncle Willy's hovering legal counsel wishes him to remind you that Uncle Willy is only providing these details for their historical interest. If you foolishly pursue making similar modifications to your own machine, you do so at your own risk! Uncle Willy doesn't want to see the Williams warranty claims department flooded with badly drilled Corvette playfields.)

Because the drop targets were removed from the design of the game, the production versions of software were never intended to support them. Therefore, when the game programmer decided to add support back in for them, so he could build himself a version of the game with the drop targets, he was forced to make a compromise: to have the released version of the software easily support both kinds of targets, it would be necessary for the drop targets to use switches, not optos. So there is the trickiest part of this conversion: he hacked some microswitches on to the circuit board in place of the optos and their supporting circuitry. He also drilled a hole in the area behind the targets, so that he could mount a rebound switch for scoring points when targets were down.

Those were the physical modifications, and here is how he wired it up:

-- The drop target microswitches were wired exactly like the standup targets had been wired before he removed them. Lower standup became lower drop target, and so on.

-- The rebound switch was wired using a white green wire (attached with the one on the trough switch) and a green/grey wire (attached with the one on the standup target to the left of the center ramp.)

-- The coil was wired using a red/black wire for power (attached with the one on the left slingshot coil) and a brown/blue wire run from connector J127-7 for the drive.

Click on an image to get a larger view...

Fig 1: The drop targets with their original stickers.

Fig 2: The drop targets down, showing the rebound switch installed behind them.

Fig 3: The rebound switch as seen from underneath the playfield. This is a tight fit!

Fig 4: The drop target assembly from underneath the playfield.

Fig 5: A closer view of the microswitches hacked onto the circuit board.

Fig 6: A picture of the original shifter assembly (which was not installed on the game Uncle Willy was taking pictures of.)