The MPU completes seven flashes and then starts over, every time.

MPU reboots right after the seventh flash

Cause: A poor joint on R134, the IRQ pull-up near U11, even when the solder looks fine.

Checks

• Tie U9 pin 40 high to rule out the reset circuit.

Fix

• Reflow R134.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Globetrotters reboots during play (GI stays on)
• MPU stops before the seventh flash: check the 43 V at R113
• Seven flashes, then it starts over endlessly
• MPU boots only some of the time
• No seventh MPU flash with a good solenoid fuse
• Good MPU stays LED-on with a PC power supply
• MPU boots only when U9 pins 39 and 40 are shorted
• Reading the MPU flash code

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)