What the two System 80 transformers supply
The large transformer C-19552 feeds the coils (24 V, and 38 V on some games), the 6.3 V AC general illumination and the 6 V CPU-controlled lamps. The small transformer B-19548 feeds the score displays (about 60 V), the 12 V supply that becomes +5 V logic, and the 8 V and 4 V display reference voltages.
The bottom panel carries 120 V AC from the wall; unplug the game before touching the line filter, fuse block or transformers.
Systems
Related tips
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Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)