A group of lamps in one row of the lamp matrix never light, even in lamp test. (The inlane lamps that stay on all the time are normal: on this game they are lit with the GI.)

Several lamps in one matrix row won't light: rusty sockets, diodes and joints

Cause: Rusty lamp sockets, failing lamp diodes and cracked solder joints along that lamp string, helped along by shaker motor vibration.

Checks

• Run the lamp row and column tests to see which lamps in the matrix are affected.
• Wiggle the lamp board connectors; cold joints on the male header pins are the most common lamp board fault.
• Check continuity pin by pin from the connector to each socket and diode in the string.

Fix

• Replace the corroded sockets and their diodes, and reflow every joint in the affected string.

Systems

• Data East CPU Version 3

Games

• Jurassic Park

Related tips

• A group of clock lamps never light with good wiring: reseat the bulbs in their sockets
• A whole row or column of lamps is stuck on and extra bright
• One insert stays dark with good bulbs and sockets: failed diode on its lamp board
• Test a lamp socket diode in place
• One controlled lamp never lights, bulb is good
• Lamps in a row or column light twice per sweep
• Lamp socket diode orientation and 555 socket contacts
• Lamp matrix fault with good transistors: check R55 to R62

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