Obsolete chips on System 3 to 7 CPU boards
The MC6875 clock chip on System 3 and 4 boards is obsolete and very hard to find, though it seldom fails. The 8T28 and 8T97 bus chips are also discontinued; the 8T97s can be replaced with 74LS367 or 74LS365, and the 8T28 data buffers can often be bypassed (see those entries).
Systems
Related tips
- Identifying a System 3 to 7 CPU board
- What changed on the System 6A CPU board
- System 6 CPU board test points
- System 7 CPU board test points
- System 6 CPU board jumpers J1 to J6
- A System 7 CPU board can run any System 3 to 7 game
- Run a System 6/7 CPU board on +5 V only
- CPU chip types: 6800 on System 3/4, 6802 or 6808 on System 6/7
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)