Start at top and do 1 step at a time till problem solved
1. Make sure both potentiometers or volume knobs are clean by twisting them and using a contact cleaner. There is a volume knob on the soundboard.
2. Pull soundboard out and check for cold solders on the connector pins on the back of board
3. Reseat any chips on the soundboard that are in chips seats
4. New connector for sound board maybe needed to b made
5.Lastly caps may need replaced on sound board
Sometimes it is more than this. Sometimes you can actually see a burned area on the board with catastrophic component failures.