You could test to see if you have audio on the RCA outputs. If so, it's a better sign than if not. It means the audio circuitry is functioning. If not then maybe you have a component failure on the main board. Hmm, I just thought of something else. One of the pins on the cable connector might be a mute signal. Maybe that Keg has a bad pin or solder connection, or is shorting that pin somehow.
Just a thought, I'm not sure if there's really a pin that does that.