The dot matrix display is blank or shows faults.

Dot matrix display blank or faulty

Cause: Loose connector, blown fuse, missing supply voltage, or a failed display.

Checks

• Make sure every display connector is seated.
• Check the related fuses.
• Measure all the supplies the display needs.
• Run the display test and check every row and column; at the end "RAM OK" should appear for the controller memory.

Fix

• The display glass unit itself is not owner-repairable; replace or send it out if voltages and connectors are good.

The display runs on high voltage; switch off before handling it or its cables.

Systems

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

Related tips

• Blank display, garbage or diagonal lines: reseat ribbon cables
• Dot matrix display supply voltages
• Dot matrix display faults
• Dot matrix display power connector pinout and voltages
• One or two display columns stuck on
• Resets caused by a failing dot matrix display
• What the WPC dot matrix controller does
• Rebuilding the dot matrix high voltage section

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer