Every controlled lamp in one column (column 7 here) works only intermittently; pressing on the board connector brings them back, usually for the rest of the game.

Whole lamp column works only intermittently: reflow the board header

Cause: A cracked solder joint on the board's header pin for that lamp column. The joint can look almost normal, showing only a tiny pinhole next to the pin.

Checks

• Label and photograph the connectors, pull the board, and inspect the solder side of that header closely.
• If the connector housing or pins are browned or burnt, plan to replace them rather than just reflowing.

Fix

• Reflow every pin on the header (not just the suspect one) with fresh solder, then refit the board, making sure each plug sits on the right pins.

Systems

• Williams System 11

Games

• Grand Lizard

Related tips

• Testing lamp matrix columns with a test socket
• A row or column of lamps stuck on and very bright
• Lamp matrix fault with good transistors: 0.4 ohm resistors
• System 11 lamp matrix basics
• Testing lamp matrix rows with a test socket
• Quick lamp row test: ground the row driver tab
• Lamp matrix still wrong after replacing transistors: upstream parts
• No sound after board work: 1J15 and 1J16 swapped (they aren't keyed)

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