The A26 board and entering self-test
The A26 board inside the coin door has the volume control, the tournament toggle and a yellow test button. The test button opens audits and adjustments; press it three times for diagnostics, then use it to step through the nine tests. The slam switch exits.
Systems
Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)