Music and effects are being generated but are extremely faint, even with a new volume pot and good speakers. Occasionally the sound crackles and comes back loud for a few seconds before fading again.

Sound barely audible though music plays: rebuild the aux power supply connector

Cause: A poor connection at the auxiliary power supply connector was starving the sound amplifier of power.

Checks

• Inspect the auxiliary power supply connectors for darkened, loose or worn pins.
• Measure the amplifier supply voltage while the sound is faint, wiggling the connector.

Fix

• Rebuild the aux power supply connector with new housing and pins (and new header pins if worn).

Systems

• Gottlieb System 3

Games

• Deadly Weapon

Related tips

• Gottlieb System 3: loud screeching from the speakers: replace the sound board capacitors
• Gottlieb System 3: constant hum from the speaker at idle
• Where the boards sit in a System 3 dot matrix backbox

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