51SYMPTOM CAUSE SOLUTIONUnit does not function when Main • No AC Power • Make certain AC power cord is plugged into a live outletPower Switch is turned on• Check whether outlet is switch-controlledDisplay lights, but no sound • Intermittent input connections • Secure all input and speaker connectionsor picture• Mute is on • Press Mute Button• Volume control is down • Turn up volume controlNo sound from any speaker; • Amplifier is in protection mode • Check speaker wires for shorts at receiver and speaker endsPROTECT message appears on due to possible shortfront panel • Amplifier is in protection mode • Contact your local Harman Kardon service centerdue to internal problemsNo sound from surround or • Incorrect surround mode • Select a mode other than Stereocenter speakers • Input is monaural • There is no surround information from mono sources• Incorrect configuration • Check speaker configuration• Stereo or Mono program material • The surround decoder may not create center- or rear-channelinformation from nonencoded programsUnit does not respond to • Weak batteries in remote • Change remote batteriesremote commands • Wrong device selected • Press the AVR Settings Button• Remote sensor is obscured • Make certain front-panel sensor is in line of sight of remoteor connect an optional remote sensorIntermittent buzzing in tuner • Local interference • Move unit or antenna away from computers, fluorescentlights, motors or other electrical appliancesLetters flash in the channel indicator • Digital audio feed paused • Resume play for DVDdisplay and digital audio stops • Check that the correct digital input is selectedSurround Back Speaker settings • Multizone system has been turned • Use the menu system to access the Zone 2 menu and reassigncannot be accessed, and test tone on, and the surround back channels the surround back channels to the main roomdoes not play through Surround were reassigned to multizone operationBack SpeakersThe XM Preview Channel (001) • XM antenna is not plugged in • Use an XM antenna module designed for use with XM Ready homeis silent audio equipment, and plug the module into the XM Radio Jack• XM antenna is not located in such • The XM antenna module needs an unobstructed view of thea way as to enable reception southern sky, or to be within range of an XM terrestrial repeater;if necessary, purchase an extension cable from your XM RadiodealerUnable to activate Program mode • Source Selector not held for at least • The selector will light as you initially press it, and go dark as youon remote 3 seconds hold it down; wait 3 seconds for the selector to light againRemote buttons light, but AVR does • Remote is in Zone 2 mode • Slide the Zone Switch at the bottom of the remote to thenot respond Zone 1 positionAdditional information on troubleshooting possible problems with your AVR 3550HD, or installation-related issues, may be found in the list of “FrequentlyAsked Questions”, which is located in the Product Support section of our Web site at www.harmankardon.com.TROUBLESHOOTING GUIDE