Score displays occasionally show random segments.

Score displays show garbage now and then

Cause: Oxidized or loose display connectors.

Checks

• Check the connectors on the back of each display.

Fix

• Unplug and reseat each display connector a few times to clean the contacts.

The display supply runs at 170-230 volts DC; touch nothing on the high-voltage section with the game on, and let it discharge before working on it.

Systems

• Bally 6803

Related tips

• Display drive signals missing at J2
• High-voltage input fuse FU2 blows
• Score displays dead or dim: high-voltage section parts
• Turn the display voltage down to 170 V
• One segment always on and the other display corrupted: replace the 74HC373
• Rebuild the high-voltage display supply

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)