U11 must be a 74HC123AN
Replace the CPU board U11 only with the HC family part, ideally the AN-suffix version. A 74LS123 will stop the board booting or make it reboot.
Systems
Related tips
- CPU board will not boot, or keeps rebooting
- Game resets every two seconds
- Gottlieb System 3 CPU passes test ROM, then watchdog trips: torn trace and wrong parts
- CPU board 26285 versus 26285-1
- Game stuck showing the last four high scores
- CPU board EPROM and RAM size jumpers
- Main chips on the CPU board
- CPU board connector uses
Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)