Memory error continues with fresh batteries.
New batteries but still a memory error: check D25
Cause: The blocking diode D25 beside the batteries has failed and is not passing battery power.
Checks
- With the game off and the meter on DC volts, put the black probe on the GND test point (just above the battery holder).
- Red probe on the plain end of D25: about 4.5 V.
- Red probe on the banded end: about 4.2 V. No voltage means D25 is bad.
- Also look for about 4.2 V at the B+ test point just right of D25.
Fix
- Replace D25 with a 1N4001 or 1N4004.
Systems
Related tips
- Always check the coil diode when a driver transistor has failed
- Test each lamp column driver with a test lamp
- Switch row (return) circuit on the CPU board
- Test the switch column drivers with a diode jumper
- Test the switch row inputs with a diode jumper
- Move the CPU batteries off the board
- Optos test good but still don't work: the opto board
- Coil diode and wire orientation when replacing a coil
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)