CPU plug A1J7 (playfield switches) pins

Pin 1 outhole (grey/orange/orange); 2 strobe 0; 3 strobe 1; 4 strobe 2; 6 strobe 4 (black/green/green); 7 strobe 3; 8 ground; 10 return 7 (orange/blue/blue); 11 return 6; 12 return 0; 13 return 1; 14 return 2; 15 return 5; 16 return 4; 17 return 3; 5 and 9 unused.

Systems

• Gottlieb System 1

Related tips

• Test PROM switch actions
• Testing switch return buffers Z9 and Z28
• System 1 switch matrix layout
• Logic-probing the switch matrix
• Switch strobes missing at Z8
• Slam and outhole switches sit outside the matrix
• Clamp diode mod to protect U5
• Check the TC3 jumper plug on the CPU board

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)