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Denon AVR 2309 trouble

I have bought Denon in Profishop in 2009 as a new one. It is used in set of homecinema in Mode 7 +1. Now something wrong happend and only the both Front and Central Speakers are working - SW, sides and back Speakers no sound.
I have tried everinthing possible describing in setting part of Manual incuding a rewritting of firmware, but without any result.

Has anyone any expriance how to fix it?

Thanks for your each advice.