Game manual schematics may show the wrong System 11 generation
Many System 11 manuals print schematics for a different board generation than the game uses; many 11C manuals (Diner, for example) show 11B schematics. A note on the sound section reading "removed in certain assemblies" is the clue. Check the board actually in the game before trusting the drawing.
Systems
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)