After fitting a brand-new replacement power supply board, the game would not work properly and the fault took days to find.

Replacement power supply board won't run the game: J2 ground pin not linked

Cause: On the new board, pin 9 of connector J2 was not connected into the ground chain with pins 10 and 5 on the solder side (either never connected or broken when the plugs were fitted).

Checks

• Check continuity between the ground pins of J2 (pins 5, 9 and 10) on the new board.
• Compare every connector pin's continuity with the schematic before suspecting other boards.

Fix

• Link J2 pin 9 into the ground chain with pins 10 and 5 (add a jumper on the solder side).

Systems

• Bally MPU AS-2518-35

Games

• Future Spa

Related tips

• The three Bally rectifier boards
• Replacing the -49 VARO pair with one bridge
• How the pre-Xenon power supply works
• Make sure the power cord has its ground prong

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