PINBALL REPAIR : ATTACK FROM MARS MPU (WPC-95) Batteries Deplete Rapidly
From day one after purchasing my Attack From Mars, I had an issue of getting the dreaded Factory Settings Restored error after several weeks of game play after replacing the batteries on the MPU. I found this to be quite odd since the batteries should be lasting years and not weeks. I looked at the MPU and found no corrosion or any kind of problems with any of the circuit chips. I thought maybe it could be the D1 and D2 diodes on the board. Diode D1, a 1N5817, is used to keep the battery pack from powering the entire MPU board when the games’s power is turned off. Diode D2, a 1N4148, is used to keep the MPU board’s logic power from charging the batteries in the battery pack. I replaced both diodes with new ones and the machine has been working perfectly without the batteries draining after a couple weeks.
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