After a firm knock on the cabinet the sound jumped to full volume, louder than it could ever be set before, and turning the volume pot no longer brings it down.

Volume suddenly goes to full blast and the volume pot does nothing: shorted pot wiring

Cause: A short in the wires between the volume pot and the sound board (they had been damaged, most likely by mice).

Checks

• Reseat the connectors along the top edge of the CPU/sound board.
• Unplug the volume pot's connector (J16 here): if the sound changes, look along the pot wiring for chewed insulation or wires touching.

Fix

• Repair or replace the damaged volume pot wiring.

Systems

• Williams System 11

Games

• Road Kings

Related tips

• Which System 11 sound board each game uses
• D-11297, D-11298 and D-12338 sound boards
• How System 11 makes sound
• Using a D-11581 sound board in other System 11 games
• Power-on sound tones and what they mean
• The D-11581 sound board: chips and ROMs
• CPU sound diagnostic switch SW1 results
• Game-over music missing: reflow the sound board header pins

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