The slam switch must be closed for the game to run

Gottlieb's coin door slam switch is normally closed. If it, or the wiring and connectors back to the CPU, is open the board will not really boot and no game can start.

Systems

• Gottlieb System 1

Related tips

• Permanently defeating the slam switch on the CPU board
• Displays light at once showing zeros
• CPU board reset circuit check
• Gottlieb reset circuit update
• Slam and outhole switches sit outside the matrix
• Test PROM switch actions
• Testing switch return buffers Z9 and Z28
• Diagnostics run without the game PROM

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