Fitting a new switch diode the right way round

Use a 1N4004 (1N4002 or 1N4001 also work) with its band the same way as the old one, or copy a working switch. On most switches the green (column) wire is on the center lug, the white (row) wire and the non-banded diode end share the lug nearest the center, and the banded end goes alone to the far lug. The manual notes exceptions, such as the zero-position head switch on Bride of Pinbot.

Systems

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

Related tips

• Testing a switch diode out of circuit
• Switch diode failures and what they look like
• Fit a replacement switch diode the right way round
• Testing CPU switch rows and columns with a diode and clip lead
• Testing a microswitch diode without unsoldering it
• System 80 switch matrix diodes
• Spare diodes for coils and switches
• Test the switch column drivers with a diode jumper

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