The 300 V circuit on Hot Tip and Lucky Seven supplies

The first two System 3 power supplies carry two extra 1N4001 diodes and two .22 mfd MKP capacitors that triple the AC into a 300 V display ionizing feed. It was dropped from World Cup on; a failed 300 V circuit need not be repaired, and the parts can be removed when the board goes into a later game.

The display supply runs at about 100 volts DC; work with the game off and the capacitors discharged.

Systems

• Williams System 3

Games

• Lucky Seven

Related tips

• Swapping power supply boards between generations
• Power circuits in a System 3-7 game
• Display supply low (under 90 V) after the resistors are changed
• Cross the legs when MJE15030/15031 replace SDS201/SDS202
• High-voltage supply rebuild parts, System 3 to 11C
• Fitting the high-voltage kit
• Spare diodes, capacitors and resistors for System 3-7
• The unregulated 12 volts can read 10 to 14 V

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