First check the speakers by connecting to front connector if thr no sound then replace the speakers.If you here sound while swap the rear amp IC might be damaged replace the IC .
Always make sure that your computer settings for audio are checked and set accordingly and that all the equlizers and audio programs that are installed and controlling your audio sound output are accounted for and adjusted properly.
One Question, does the remote controller work? If so I had the same problem, I just used the remote whenever I needed to change settings. That is a temp solution instead of opening your device and changing stuff.