I think you need to look at the sound settings. In particular the type of sound. HD channels often carry AAC sound, suitable for Dolby 5.1 and Standard Channels don't. So the sound system will switch modes when you change channels. However the receiver is not switching back to picking up PCM signals, the type used on SD channels.
I also have the problem of no center display but I do have sound.
On my avr 7000 I am sure that the display is not functioning but on yours try holding the middle select button for three seconds as in the manual this is how you turn the display brightness back on.
I have no clue why they have made it able to be turned off lol
If i'm right, the system powers down as a safety precaution. It prevented itself that it will breakdown. It's your choice but I recon you can just enjoy and listen to your favourite music.
Check all speaker connections for shorts, and make sure all cables are secure, no change! There may be a problem in the audio output stage, at this point you will need somebody to check out the unit because the problem can be hard to locate.
The display is powered almost directly from the transformer. Very few parts in between. It could be the display itself, which I guess is an expensive repair...
But I have just fixed my display for the second time by re-soldering a connection, and you may be just as lucky ;-) Both times the problem has been a bad connection in resistor R810 on the front PCB. Not easy to get to, but if you loosen the front a little bit you can find R809 and R810 on the left side of the front PCB.
Power goes from the mains transformer (6,8V AC) through a couple of connectors, and then through R809 and R810 before reaching the display itself (on pins 1 and 58). If you are careful you can measure the voltage at the display when the front of the receiver is tilted slightly forward.
