Swapping power supply boards between generations

Power supply boards largely interchange from System 3 to 7. Hot Tip and Lucky Seven boards also carry a 300 V display feed and a GI fuse. System 7 boards add GI connectors 3J7, 3J8 and 3J9 and a GI relay, which go unused in a System 3 to 6 game.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Games

• Lucky Seven

Related tips

• The 300 V circuit on Hot Tip and Lucky Seven supplies
• What the power supply board takes in and puts out
• Test the power supply with its outputs unplugged
• 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
• Burnt GI plugs on the power supply board
• Power circuits in a System 3-7 game

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)