After the game was taken apart for a cabinet restoration and reassembled, the dot matrix display shows only random garbage. A known good power supply makes no difference, and fuses, connectors and ribbon cable orientation all check out.
DMD shows random garbage after reassembly: failed display driver board
Cause: The display driver (controller) board had failed.
Checks
- Recheck every connector and ribbon cable put back during reassembly (orientation and position).
- Swap in known good parts one at a time: display, power supply, then the display driver board. Boards from other games of the same generation (a Jurassic Park here) can be used for the test.
Fix
- Replace or repair the display driver board.
The display circuits use high voltage: switch off before unplugging or swapping display boards.
Systems
Games
Related tips
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- Data East/Sega: PPB fuse and backbox fuse blowing: shorted Q3 and a plug one pin over
- DMD keeps resetting in attract mode: torn ribbon cable at the display controller
- Whole outer frame of DMD dots dead: pins snapped off the display glass
Source: Pinball Repair help group!! (Facebook group)