Convert a -35 MPU to a -133 for Baby Pac-Man and similar games

Steps

• Remove the 2K resistor at R113.
• Fit a 1N4148 (or 1N914) diode with its band toward capacitor C1 and the unbanded end toward J4 pin 15 (band away from J4).
• Set the ROM jumpers for the EPROMs the game uses.

Systems

• Bally MPU AS-2518-35

Games

• Baby Pac-Man
• Grand Slam
• Granny and the Gators

Related tips

• Converting a -133 MPU to a -35
• Bench-testing a -133 MPU: swap the R113 diode for a resistor
• Still no seventh flash with F4 good
• Bally-35 MPU: remove the on-board rechargeable battery before it leaks
• MPU boots only some of the time
• MPU LED locked on with no flicker: likely causes
• Testing the MPU reset circuit at U9 pin 40
• Single reset parts that hold the LED on

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)