The game shows a checksum error.

"Checksum Error" at power-on

Cause: A bad game ROM (U6 on a WPC CPU board).

Fix

• Replace the game ROM with the correct version for the game.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C
• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• "U6 Checksum Error"
• G10 error with serial number all zeros
• Signals a dead CPU board should show
• Schematics may show W1/W2 as a display-type setting
• CPU board completely dead
• Dead CPU: check the reset and IRQ lines
• Settings are lost at power-off even with fresh batteries: bad battery diode D2
• Blanking LED wrong, or all solenoids pulse and blow a fuse at power-on

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer