Switch matrix connector pins and their chips
On 2J2 and 2J3, pin 1 is column/row 8 and pin 9 is column/row 1. 2J2 pins 1-3 and 5 (columns 5-8) are driven by IC18 (7406); 2J2 pins 6-9 (columns 1-4) by IC17 (7406). 2J3 pins 1 and 3-5 (rows 5-8) go to IC16 (4049); 2J3 pins 6-9 (rows 1-4) to IC15 (4049). The 6821 PIA at IC11 handles all of it.
Systems
Related tips
- Switch matrix column test at 2J2 with Leon's code
- A ball resting on one switch stops others in its column
- Lamp matrix row test at 2J7 with Leon's code
- Damage after the black and white plugs were swapped
- Lamp rows stuck on: the 7406 at IC19
- One switch closing lights up its whole row in switch test: bad column driver chip
- Logic chips worth stocking
- Logic-probe the switch matrix
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)