Every switch in one column of the switch matrix fails to register in switch test.

Whole switch column dead and board fails the jumper test: column transistor

Cause: The column drive transistor on the CPU board (a 2N3904, Q12 here) had failed. A reversed coil diode found earlier on this game may have contributed.

Checks

• Enter switch test, unplug the switch row and column plugs at the CPU board, and touch a clip lead from a pin of the column plug header to a pin of the row plug header (1J8 to 1J10). Try a working column first to prove the test.
• If the bad column never registers with the plugs off, the fault is on the board; test the column transistor with the meter's diode test against a good one.

Fix

• Replace the column's 2N3904 transistor.

Systems

• Williams System 9

Games

• Space Shuttle

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