Use #47 bulbs instead of #44

#47 bulbs draw less current and run cooler than #44, which spares the connectors and driver board. Keep 20 to 50 of them, plus about 10 #89 flash bulbs.

Systems

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

Related tips

• How the lamp matrix runs 6.3 V bulbs on 18 V
• A single lamp does not light

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