A1 CPU board plug wire colours

A1J1 (+5 V): pins 1 and 2 blue/gray/gray. A1J4 (sound): violet/violet/orange on pin 1 and orange/blue/blue on pin 2. A1J5 (switch returns): pin 1 blue/violet/violet (often absent), pin 2 blue/blue/blue.

Systems

• Gottlieb System 3

Related tips

• Checking and setting +5 V at the CPU board
• CPU board 26285 versus 26285-1
• Main chips on the CPU board
• CPU board connector uses
• Reading the CPU board LED
• Booting a CPU board on the bench
• CPU battery and socket parts
• Missing P6 or P7 header on the CPU board is normal

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