Entering and stepping through System 11 diagnostics

Steps

• Press the centre coin-door button (usually red, "Auto Up/Manual Down") so it latches down.
• Press Advance (usually the button nearest the door): the display shows DISPLAY TEST.
• Press the centre button so it latches up: the display test runs digits 0-9 then every segment. Press the centre button down to freeze it.
• With the centre button up, press Advance to go to the next test. Some tests need the Start button.
• There is no way to step back; to repeat an earlier test, power the game off and on and enter diagnostics again.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)