When I play a DVD with Dolby digital, the unit keeps shutting down saying "overload" I checked the speakers, Unplug the AC. Even if I keep the volume down as low as 5,. In analog, it works much better,shuts down every few hours.In Digital I cant get threw 5 mins. This JUST started happening. The unit is 3 to 4 years old and ON all the time..Up until last week it played Dolby digital just fine., This is 6/10. I have opened the unit and visually can not see a shorted board. Thanks, John