The 43 V coil supply is pulled down or missing in strange ways.

Odd 43 V coil faults on games with the early AS-2518-32 sound board

Cause: The early AS-2518-32 sound board (Lost World to Dolly Parton) makes its 12 V from the 43 V with a simple divider/regulator that can fail shorted, grounding the 43 V.

Checks

• Unplug power to the sound board and recheck the coil supply.

Fix

• Repair the sound board regulator section if the fault clears with it unplugged.

Systems

• Bally MPU AS-2518-35

Related tips

• Identifying AS-2518-51 and AS-2518-56 sound boards
• AS-2518-51/-56 sound board jumpers
• No sound and no 12 V at the sound board test point: burnt-open R22
• Sound module -32 and -50 test points
• Bench-test a -51/-56 sound board with a test EPROM
• Sound Plus -56 and vocalizer test points
• No sound at all: start with the amplifier hiss
• Which -51/-56 sound ROMs respond to the board test button

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