The sound board gets no power, so there is not even a hum from the speaker, although the same board works in another game.

No sound and not even a speaker hum: bad crimp on the sound board's 12 V feed

Cause: A badly crimped terminal on a doubled-up wire carrying 12 V to the sound board. On these games the 12 V leaves the solenoid driver board (J3 pin 11) and runs to the sound board before carrying on to the MPU.

Checks

• Measure DC voltage at the sound board's power pins to ground.
• Find the wire colour leaving the solenoid driver board for the sound board supply and follow it to the sound board connector.
• Inspect any terminal holding two wires; these often get a poor crimp.

Fix

• Recrimp or replace the bad terminal on the doubled wire.

Systems

• Stern MPU-200

Games

• Seawitch

Related tips

• Sound very low and the volume knob does nothing: bad crimp on the volume pot wire
• Sound module -32 and -50 test points
• Game locks up after the seventh flash
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• Top pop bumper dead, new coil blows the 1 A playfield fuse at power-up: bad driver
• Never use a TMS2716 EPROM

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