A PIA output pin stays high or low while the others switch.
One PIA output does not toggle under the test EPROM
Cause: Either the PIA is faulty or something on that output line is shorted.
Checks
- Briefly bridge the stuck pin to the toggling pin beside it. If the stuck pin starts toggling, the PIA is bad. If both stop, there is a short on the output line or the PIA itself is bad.
Fix
- Replace the PIA (socket it), or trace and clear the short.
Systems
Related tips
- CPU board PIA positions and jobs
- Test EPROM flash codes: which chip failed
- Which logic chips drive which solenoid transistor pairs
- Whole switch column dead after working under the playfield
- Switch column (drive) circuit on the CPU board
- How a coil or flasher is switched: PIA to TTL to pre-driver to driver
- Segments missing or stuck on: CPU board PIAs 9B and 7B
- One switch column dead: parts to check in order
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)