System 80 diagnostic tests 16 to 20
Test 16 pulses the general relays and coin lockouts and lights every CPU lamp; coils driven through under-playfield transistors also fire. Test 17 pulses solenoids 1, 2, 5, 6, 8 and 9 and skips 3, 4 and 7, which are the coin meters. Test 18 shows 99 when no switch is closed, otherwise the matrix number of a closed switch; work each switch by hand. Test 19 lights each display digit in turn. Test 20 checks the memory chips.
Systems
Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part Two, Clay Harrell (pinrepair.com)