Use a 2732 instead of a 2532 at U17 on a System 7 CPU board
Steps
- On the component side, remove jumper W22.
- On the component side, fit jumper W23.
- On the solder side, cut the wide +5 V trace that feeds U17 pin 21 (it runs just above pins 13 to 24). Make a clean cut so +5 V cannot touch ground.
- On the solder side, solder a jumper between U17 pin 21 and the W22 pad nearest U17 pin 1 (the pad marked 22). Using the other pad would short pins 18 and 21.
- Fit the 2732 at U17.
Systems
Related tips
- Identifying a System 3 to 7 CPU board
- System 7 CPU board test points
- Run a System 6/7 CPU board on +5 V only
- Which CPU boards can run which system firmware
- System 7 CPU ROM sockets
- Firepower: replace the three PROMs with one 2732 at IC14 ("ZIG" method)
- Obsolete chips on System 3 to 7 CPU boards
- Add two test LEDs to a System 7 CPU board
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)