CPU RAM at U25
U25 is a 2k x 8 CMOS static RAM in 24 pins: 2016, 6116-L or NTE2128. Early schematics call it a 5177, which a 6116 replaces. Pin 24 (battery-backed supply) sits opposite pin 1, marked by the dot.
Systems
Related tips
- U15 CPU and U25 RAM substitutes
- Testing U25 RAM with Leon's EPROM
- Checking ground and +5 V on the CPU board
- System 11 NVRAM upgrade not working: fit it at U25, not U23 (sound RAM)
- Which System 11 CPU boards fit which games
- Running the CPU board on the bench
- Checking the CPU clock signal
- CPU board test switches SW1 and SW2
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell