All lamps in one column (or one row) are on constantly.
A lamp column or row stays on all the time
Cause: A column stuck on is usually a shorted TIP107; a row stuck on is usually a shorted TIP102.
Checks
- Identify whether the stuck lamps share a column or a row from the lamp matrix chart.
Fix
- Replace the TIP107 (column) or TIP102 (row).
Systems
Related tips
- A row or column of lamps stuck on and too bright
- How the WPC lamp matrix works
- How the WPC lamp matrix is switched
- WPC lamp matrix and GI driver parts
- Which transistor drives which WPC solenoid and lamp circuits
- BR1 (D11-D14 on WPC-95) and the board around it scorched
- Where the WPC coil and lamp drivers sit
- How a WPC coil, flasher or lamp driver chain works
Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)