All lamps in a row or column glow bright all the time.

A whole lamp row or column is stuck very bright

Cause: A shorted row or column driver transistor.

Fix

• Replace the shorted driver transistor named in the lamp matrix table.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C
• 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
• A lamp row very bright or dead
• A row or column of lamps stuck on and too bright
• Testing lamp-row drivers with a test lamp
• Testing lamp-column drivers with a test lamp
• Lamps light twice in the all-lamps sweep, or two lamps act as one
• A whole string of backbox lamps is out: blown GI fuse F110
• How the WPC lamp matrix works

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer