Several lamps stay lit and look brighter than the rest, even in attract mode or the all-lamps test.

A row or column of lamps stuck on and too bright

Cause: A shorted lamp-matrix transistor holds its row or column on, giving the bulbs more than their normal strobed share of the 18 V.

Checks

• Run the all-lamps test: every matrix lamp should flash.
• Check the manual to see whether the stuck lamps share a row or column.
• Test that row's TIP102 or column's TIP107.

Fix

• Replace the shorted transistor.

Systems

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

Related tips

• A lamp column or row stays on all the time
• 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
• A lamp row very bright or dead
• BR1 (D11-D14 on WPC-95) and the board around it scorched
• Where the WPC coil and lamp drivers sit

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