Flicker and one flash, then the sequence stops.

One flash only: U7 6810 RAM

Cause: The 6810 RAM at U7 or its socket.

Checks

• A pause between the first and second flash is normal; the RAM test takes a moment.

Fix

• Replace U7 and, if needed, its socket.

Systems

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

Related tips

• Seven flashes, then it starts over endlessly
• Three flashes only: U10 PIA
• Five flashes only: U12 timer or open R113
• Check the -51/-56 PIA, RAM and amplifier with the test EPROM running
• Leon test: type 2 sound board RAM IC11
• Flicker but no first flash
• Four flashes only: U11 PIA, R134 or a bad display
• Still no seventh flash with F4 good

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