Picture fine but no sound

go to the menu and to the setup and go to sound...make sure that the right format is selected for the movie and that the right output is selected for the output your using....if the sound is intermittand you more than likely have dry solder joins on the board...to fix this you ned to disconnect the unit from the mains and remove all screws to open the unit up and then take out the PCB and screw holding the RCA blocks and remove and use a soldering iron and solder to re-solder all connection points between to RCA array and the PCB
hope this helps,ben