System 11 NVRAM upgrade not working: fit it at U25, not U23 (sound RAM)

When fitting a 6116-type NVRAM to a System 11 CPU board, make sure you socket and replace the game RAM at U25. U23 is the RAM for the sound section on the same board; putting the NVRAM there leaves the game RAM unchanged, so the upgrade appears not to work. Take care straightening any bent pins on chips you remove, as they are fragile.

Systems

• Williams System 11C

Related tips

• Which System 11 CPU boards fit which games
• CPU RAM at U25
• Testing U25 RAM with Leon's EPROM
• U15 CPU and U25 RAM substitutes
• Using the Williams System 11 test fixture EPROM
• Which System 11 CPU boards swap between generations
• How to tell a System 11C CPU from an 11B
• Setting up Leon's System 11 CPU test EPROM

Source: Pinball Repair help group!! (Facebook group)