The MPU flickers and flashes six times (five on Baby Pac/Granny) but never gives the final flash, and the game does not start.

Every flash but the last one

Cause: The last test looks for the +43 V solenoid supply; fuse F4 on the rectifier board is the most likely cause.

Checks

• Check F4 on the rectifier board.

Fix

• Replace F4 with the correct rating; if it blows again, find the shorted coil circuit (see the F4 isolation entries).

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• F4 still blows with the playfield coils out of circuit
• Rectifier board fuse ratings (all Bally 1977-1985)
• MPU on the bench always stops one flash short
• Baby Pac-Man and Granny MPUs look for 6 V AC, not 43 V
• Good MPU stays LED-on with a PC power supply
• What a good MPU does straight after the last flash
• MPU reboots right after the seventh flash
• Seven flashes but no attract mode

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