One controlled lamp (lamp 75, an E in JUDGE) never lights, though the bulb and socket were replaced and the other lamps on the same row and column work.

One insert lamp dead with a good bulb and socket: diode on the lamp board

Cause: The lamp's diode on its multi-lamp printed circuit board had failed.

Checks

• Measure for voltage at the socket.
• Briefly jumper across that lamp's diode; if the lamp lights, the diode is bad.
• Also check the connector pins on the lamp board for cracked solder.

Fix

• Replace that lamp's diode on the lamp board.

Systems

• WPC DCS

Games

• Judge Dredd

Related tips

• Part of a lamp row or column stays off
• A lamp row very bright or dead
• A few unrelated lamps never light
• One controlled lamp out while the rest of the matrix works
• An entire lamp row or column is out
• No lamp matrix lamps light
• All matrix lamps stay on
• A lamp column or row stays on all the time

Source: Pinball Repair help group!! (Facebook group)