For about the first 15 minutes, speech is roughly half as loud as the effects.

Speech quieter than sound effects until the game warms up

Cause: Oxidized wipers in the two volume pots, or failing capacitors.

Checks

• Turn both pots back and forth quickly several times, then readjust.

Fix

• Replace the pots if it persists, then look at the board capacitors.

Systems

• Bally MPU AS-2518-35

Related tips

• Squawk and Talk: distorted sound or hum
• Squawk and Talk LED stays on and the board never boots
• The Squawk and Talk test button can lock the board up
• Squawk and Talk test points
• Bench-test a Squawk and Talk board
• Squawk and Talk supply needs
• Squawk and Talk LED flash codes
• Background sounds clear but the speech has heavy static: recap and reflow the sound board

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