All sound effects play, but the game never speaks, or the speech is very quiet compared with the sounds.

Sound effects work but speech is missing or very quiet: replace the speech board op amps

Cause: Failed op amp chips on the speech board (two 1458-type op amps here), plus a tired capacitor near the speech ROMs.

Checks

• Press the test button on the sound board: it should cycle through sounds and speech.
• Make sure speech is enabled by the sound board DIP switch and the sound/speech balance control isn't turned fully to one side (clean it if it is scratchy).
• Check the ribbon cable between the sound and speech boards.
• Try another speech board to confirm the fault is on the board.

Fix

• Replace both op amps on the speech board and the capacitor above the ROMs.

Systems

• Williams System 7

Games

• Black Knight

Related tips

• No sound effects in play though speech works: check the sound board PIA
• Setting up a sound board for speech
• Sound board jumpers for sound-and-speech games (2K ROM)
• Speech very faint on a type 2 board
• Sound test works but sounds missing in play
• Missing words or sounds from cracked connector pins
• Speech board faults
• Garbled or partial sounds from bad ROMs or sockets

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