Random vertical or diagonal lines on the display.

Random vertical or diagonal lines: 12 V missing at the display

Cause: The 12 V from the driver board isn't reaching the display (some brands need 12 V to run).

Checks

• Measure 12 V at display pin 7 and at the driver board.

Fix

• Repair the connector or the driver board 12 V supply.

Systems

• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Repairing a missing display line with conductive epoxy
• +5 V or +12 V missing at the display
• Random display lines and all flippers energising at power-on
• Blank display, garbage or diagonal lines: reseat ribbon cables
• Dot matrix display faults
• Display looks cloudy on large or inverted graphics
• Outgassed displays and the 5 V supply
• Replace the whole display, not just the glass

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)