Four-leg U optos need the high-sensitivity grade

The pre-WPC-95 four-leg U opto is industry part QVE11233. The common grade (.0110) is often not sensitive enough for Williams circuits, and cheap generic versions usually fail to work. Look for QVE11233.0086, the more sensitive grade used in the Twilight Zone clock, which works in every other Williams position too.

Systems

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

Related tips

• Twilight Zone clock uses eight sensitive U optos
• Twilight Zone: "clock is broken" error
• Testing an opto receiver
• Opto parts to keep on hand
• Opto styles used in WPC games
• Cleaning dusty optos
• Flipper cabinet opto switch boards
• Where WPC games use opto switches

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