After moving the game, the MPU LED will not run its boot flash sequence and the game does not start. The 5 V at the MPU reads only about 4 V.

MPU LED never does its flash sequence: a filter capacitor had broken off the power board

Cause: One of the large power capacitors had broken off the board during transport and was found lying loose in the backbox.

Checks

• Measure 5 V at the MPU; anything well under 5 V will stop it booting.
• Look over the power boards for a missing or loose large capacitor and check the bottom of the backbox for fallen parts.

Fix

• Solder the capacitor back in (or fit a new one of the same value and voltage, observing polarity).

Large filter capacitors can hold a charge; switch off and unplug the game and let them discharge before handling the power boards.

Systems

• Bally MPU AS-2518-17

Games

• Playboy

Related tips

• No voltage at any rectifier board test point: burnt mains wire to the transformer
• MPU LED lit solid: check +5 V first
• No +12 V at the MPU: check the rectifier board
• Line filter, power switch and service outlet
• MPU locks with LED on because of C23 or Q20 on the solenoid driver board

Source: Pinball Repair help group!! (Facebook group)