Slam and outhole switches sit outside the matrix

Two direct inputs, each made by closing to ground, sit outside the matrix: slam at CPU A1J6 pin 2 and outhole at A1J7 pin 1. With the slam open the displays strobe fast and the game halts until it closes. The stock switch test shows the outhole as switch 12; the Ni-Wumpf test shows it as 15, and that board has no slam input at all.

Systems

• Gottlieb System 1

Related tips

• Logic-probing the switch matrix
• Test PROM switch actions
• Switch matrix dead after coil or GI voltage touched it
• Testing switch return buffers Z9 and Z28
• Switch strobes missing at Z8
• CPU plug A1J7 (playfield switches) pins
• CPU plug A1J6 (coin door) pins
• Clamp diode mod to protect U5

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