CPU board connector uses

P1 +5 V power; P2 ribbon to the driver board; P3 ribbon to the display controller or alphanumeric display board; P4 sound board; P5 switch matrix returns (slam, tilt and test returns included); P6 aux driver board; P7 communications adaptor. The CPU board takes the switch returns while the driver board drives the strobes.

Systems

• Gottlieb System 3

Related tips

• CPU board 26285 versus 26285-1
• Booting a CPU board on the bench
• CPU board EPROM and RAM size jumpers
• CPU board LED never lights
• Logic chips worth stocking
• U11 must be a 74HC123AN
• Replace a failed 6116 RAM with a 6264
• Game stuck showing the last four high scores

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)