The two System 1 transformers

The large C-17924 transformer powers coils, GI and CPU lamps and very rarely fails. The small B-17921 makes the logic and all display voltages (69 V AC plus references); it is fragile, and its 69 V display winding is the part most likely to fail.

The bottom panel carries 120 volt line power; unplug the game before touching the transformers, line filter or fuse block.

Systems

• Gottlieb System 1

Related tips

• What is on the System 1 bottom panel
• How power reaches a System 1 game
• Spare diodes, capacitors and other parts for System 1
• Testing a bottom panel bridge rectifier
• Replacement bridge rectifiers
• Coil, CPU lamp and GI supplies
• Power supply bring-up, step 1: inputs
• Bottom panel fuses on System 1

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