Missing P6 or P7 header on the CPU board is normal

Some CPU boards have no 24-pin header at P7 (the optional A27 communications adaptor) and P6 is used only on games with an A11 aux driver board. Neither is needed for the game to run.

Systems

• Gottlieb System 3

Related tips

• CPU board 26285 versus 26285-1
• Main chips on the CPU board
• 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

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