How the Williams switch matrix is scanned
Up to 64 switches sit in 8 columns and 8 rows. The CPU grounds one column at a time, reads the eight row inputs, then moves on, so each column is strobed roughly 500 times a second. A whole dead row or column therefore points at its common wire or the CPU board.
Systems
- Williams System 11
- Williams System 11A
- Williams System 11B
- Williams System 11C
- WPC Alpha-Numeric
- WPC Dot Matrix
- WPC Fliptronics
- WPC DCS
- WPC-Security (WPC-S)
- WPC-95
Related tips
- How the switch matrix reads a switch
- Testing the switch matrix with a logic probe
- WPC switch matrix basics
- Switch matrix chips on the CPU board
- Checking the switch matrix with a logic probe
- Switch matrix resistor networks and their values
- Narrowing a switch matrix fault to the CPU board, wiring or opto boards
- Coin door test buttons and special solenoid switches are outside the matrix
Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer