After a sound board recap the board's own test was perfect, but at power-up the sounds often didn't match what was happening, it took two or three power cycles to come right, and sound sometimes died mid-game.

Sounds don't match the game or die mid-game: sagging 7805 on the sound board

Cause: The sound board's 7805 +5 V regulator was failing; its output sagged to about 4.77 V.

Checks

• Measure the +5 V on the sound board while the game runs; it should be close to 5.0 V and steady.

Fix

• Replace the 7805 regulator, with heat sink compound under it.

Systems

• Williams System 6 / 6A

Games

• Firepower

Related tips

• The sound board is its own computer
• Sound board completely dead
• Sound self-test passes but some game sounds never play: bad PIA on the sound board
• Setting up a sound board for speech
• Sound board jumpers for sound-and-speech games (2K ROM)
• Powering a sound board for testing
• Sound test fine but game plays the wrong sounds: cracked joint on sound select header
• Which sound board each game uses

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