The dot matrix display lights up solid with no image at all, while the game boots, plays and makes sound normally. Unplugging the ribbon cables makes the display go dark.

DMD fully lit with no picture while the game plays: bad DMD panel

Cause: The DMD panel itself had failed, even though it still lit up completely.

Checks

• Check both ribbon cables for an offset row or bent pin.
• Measure the +5 V and +12 V at the display, and on the DMD controller board if they are low.
• Swap in a known good display or controller from another game to see which part is faulty.

Fix

• Replace the DMD panel (a used good one fixed this game). If the panel tests good, repair the DMD controller board instead.

The DMD runs on high voltage (over 100 V). Switch off and wait before handling the display or its power plug.

Systems

• WPC DCS

Games

• World Cup Soccer

Related tips

• WPC DMD shows garbage and a RAM address error: reseat the ribbon cables first
• Blank display, garbage or diagonal lines: reseat ribbon cables
• One or two display columns stuck on
• Display intermittently garbled after new driver board and cables: the DMD itself
• Dot matrix display with dark gaps or dim areas: outgassed glass
• Dot matrix display goes blurry within minutes
• Dot matrix display supply voltages
• Which dot matrix displays fit WPC games

Source: Pinball Repair help group!! (Facebook group)