The MPU stops before its last flash, yet the 43 V fuse is fine.

No seventh MPU flash with a good solenoid fuse

Cause: A bad diode on the sound board dragging the 43 V supply down far enough that the MPU does not finish booting.

Checks

• Unplug the sound board and see whether the seventh flash returns; measure the 43 V.

Fix

• Replace the failed sound board diode.

Systems

• Bally MPU AS-2518-35

Related tips

• MPU stops before the seventh flash: check the 43 V at R113
• What a good MPU does straight after the last flash
• MPU reboots right after the seventh flash
• Reading the MPU flash code
• What each MPU LED flash proves
• MPU LED locked on with no flicker: likely causes
• MPU on the bench always stops one flash short
• Game reboots at random: R11 heating Q5

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