Switch columns to U20 pins

Column 1 (J206/J207 pin 1) is U20 pin 18; column 2 pin 17; column 3 pin 16; column 4 pin 15; column 5 pin 14; column 6 pin 13; column 7 pin 12; column 8 (J206/J207 pin 9) is U20 pin 11.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Testing CPU switch columns with the switch levels test
• A whole switch column stops working: replace the ULN2803 column driver at U20
• Why CPU U20 fails and how to replace it
• Row or column "ground short" errors
• WPC-89 CPU: one switch column still dead after a short: trace U14 to U20 to J206
• Switch matrix chips on the CPU board
• One switch does not work
• Switch matrix dead after a screwdriver slip under the playfield

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)