First decide if the coil is CPU controlled

Pop bumpers, slingshots and the coin lockout coil are switched directly and never touch the CPU. Every other coil is CPU driven; find its driver transistor from the driver table before testing.

Systems

• Gottlieb System 1

Related tips

• A CPU controlled coil does not fire
• Check every coil's resistance before first power-up
• Firing coils from CPU buffers Z6 and Z7
• Gottlieb coil wrappers are colour coded
• The coin lockout coil is always powered
• Why System 1 coils lock on: the ground shift
• Lamp test can hold coils on for five seconds
• House-numbered coils need the chart, not the number

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