Converting a -133 MPU to a -35
Steps
- Remove the 1N4148 diode at CR52 (the R113 position near J4).
- Fit a 2k 1/4 W resistor in its place.
- Fit EPROMs burned with the code for the game the board will run.
Systems
Games
Related tips
- Convert a -35 MPU to a -133 for Baby Pac-Man and similar games
- Bench-testing a -133 MPU: swap the R113 diode for a resistor
- MPU stops before the 7th LED flash (no 43 V)
- Still no seventh flash with F4 good
- Convert a -133 MPU to a -35
- 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
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Two, Clay Harrell (pinrepair.com)