After a rebuild with a new replacement MPU (plus new rectifier and solenoid driver boards) the game plays, but the sound is harsh and static-like and breaks up whenever a target or coil is hit.

Sound breaks up into static after fitting a replacement MPU: do its master reset

Cause: The new replacement MPU had not been given a master reset after installation, so its stored settings were not right for the game.

Checks

• Measure the rectifier board test points and the transformer outputs first, to rule out a power problem.
• Check the sound board ground.

Fix

• Perform the master reset described in the replacement MPU's instructions, then check the sound again.

Systems

• Stern MPU-200

Games

• Meteor

Related tips

• Sound module -32 and -50 test points
• No sound and not even a speaker hum: bad crimp on the sound board's 12 V feed
• Sound very low and the volume knob does nothing: bad crimp on the volume pot wire
• Game locks up after the seventh flash
• A display not working from MPU or sound board faults
• Never use a TMS2716 EPROM
• Drop target banks won't reset after new targets: springs too short and stiff

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