The game plays normally but shows a zero cross error every time it starts up. Swapping in another power supply makes no difference.

Zero cross error at power-up: replace the driver-to-CPU interconnect cable

Cause: The zero cross signal is made from the AC line on the driver side and passed to the CPU board over the interconnect cable. A tired cable with an intermittent conductor caused the error even though it passed a simple continuity test.

Checks

• Check the power supply and the cable between the power supply and the CPU board.
• Look for cracked solder joints at the cable headers on both boards.
• Use the CPU board schematic to find the zero cross input and its connector.

Fix

• Replace the interconnect cable that carries the zero cross signal from the driver board to the CPU board.

Systems

• Capcom

Games

• Big Bang Bar

Related tips

• The CPU memory battery is built into a non-socketed RAM chip
• Where the boards sit in a Capcom backbox
• Capcom: check driver board power connectors J9 and J12 for heat damage
• Checking and reseating solid-state board connectors

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