What the power supply board takes in and puts out
The board takes 18.6 VAC (twice 9.3 VAC) and makes +12 and +5 VDC, and takes 90 VAC to make +/-100 VDC. The 28 V coil and 18 V lamp supplies come from the backbox bridges and pass through the board only for fusing. The sound board has its own supply, so a sound fault is not a main power supply problem.
Systems
Related tips
- Test the power supply with its outputs unplugged
- Swapping power supply boards between generations
- No +5 V on a System 3-6 power supply
- No +5 V on a System 7 power supply
- Early Black Knights use the System 6 power supply
- Power circuits in a System 3-7 game
- Parts of the 28 V solenoid supply
- No coils fire: check the 28 V solenoid supply
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)