A Failed Backbox Lamp Matrix Fuse Makes DMD Games Look Very Broken.... voir pinrepair.
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If the backbox 18 volt lamp matrix fuse (8 amp slo-blo, with the blue/white wire connecting to the fuse holder) fails, this can cause the dot matrix display to "crash", causing these problems. Another way to identify this problem is the lack of any playfield CPU controlled lighting. The game will "play" (that is, the game will start and play balls), but with score display problems and no CPU controlled lamps. Simply replacing the 18 volt lamp matrix fuse (in the backbox) will fix this problem (providing the associated components such as the bridge and capacitor are OK).
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-------->>>>>If there is a lamp matrix power short, or the lamp matrix backbox bridge is bad<<<<<
, the problem will need to be fixed or the fuse will continue to immediately fail.
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This problem occurs because the +12 volts needed for the dot matrix display is generated by the 18 volt lamp matrix bridge and the capacitor/fuse bolted inside the backbox (through connector CN5 on the power supply). The 12 volts generated by the power supply board (for the sound board which comes from connector CN6), does not provide this voltage to the dot matrix display! Hence the power supply could be working perfectly, and this problem could still exist.