Suddenly my (at the time of purchase) high tech, A/V receiver stopped offering audio; instead it displayed “ERROR ACK” in a flashing motion (approximately one second on, one second off) in the display. A call to Marantz directed me to a “local” authorized repair shop, about 40 miles away. With a fixed price $249 bill, it would be cheaper for me to futz with it myself or buy a replacement on eBay.
I tried to reset the receiver by pressing CLEAR and DISPLAY OFF simultaneously and holding about five seconds until you can hear the relay click. Unfortunately, this just reset my settings, but did not make the error message go away. Next, I did the unthinkable – disconnect all wires from the back of the unit (with the unit powered off and unplugged). I turned on the receiver and no more error! I believe the message had to do with one of the inputs (probably digital) having an error in the communication.
I attempted to disconnect some of the digital inputs with the unit on prior to attempting this procedure with no success. If I had to do it again, I would disconnect one at a time, each time cycling the power prior to disconnecting the input.