The score displays flicker or are dim.

Score displays flicker or go dim

Cause: The display supply filter cap C6 (200 mfd 150 V) has dried out; C4 is also worth replacing.

Checks

• Measure the +60 V and +42 V outputs at A2-P3.

Fix

• Replace C6 with 200 mfd 150 V and replace C4.

The display supply runs at 60 to 69 volts; work on it with the game off and never plug or unplug display connectors with power on.

Systems

• Gottlieb System 1

Related tips

• Power supply bring-up, step 3: displays
• +60 V or +42 V display voltage missing
• Use C6 negative as ground when measuring 60/42 V
• Display high-voltage section of the power supply
• Logic and display reference section of the power supply
• System 1 power supply shows about 110 V where 4 V and 8 V belong: wrong ground
• Quick checks on the similar System 1 power supply
• Spare transistors for System 1 boards

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)