The MPU gives all seven flashes but the game never enters attract (game over) mode; or, with any DIP switch on, some score digits light for about five seconds and then every display blanks.

Seven flashes but no attract mode

Cause: Missing balls or a faulty trough switch on multiball games, or (especially on Stern MPU-200 boards) a 5101 RAM that is too slow even though it passed the self-test. The slam switch is not the cause.

Checks

• Make sure every ball is fitted and the trough switches work.
• Check the speed rating of the 5101 RAM(s).

Fix

• Fit faster 5101 RAMs (a PCD5101P suits every board).

Systems

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

Related tips

• Use a fast enough 5101 RAM
• Game locks up entering bookkeeping after a battery change
• Seven flashes, then it starts over endlessly
• Garbled player 1 display and strange play from a bad 5101 RAM
• MPU LED never lights at all
• MPU stops before the 7th LED flash (no 43 V)
• Six flashes only: 43 V, U10 or U14
• M-200 flashes seven times but the game misbehaves or repeats one number in audits

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