I am New and need some help. Onkyo tx-sr707 dropping left rear channel

I have a Onkyo TX-SR707 and i am having problem with the left rear channels dropping audio. I get static some times, but then sometimes i hear very little sound, and then sometimes i get nothing. Also when i lisen to music , i.e. aux ipod hook up 3.5mm to left and right audio inputs to front of the reciever i use 5 ch audio and i can get audio out of the left rear. I have done a master reset several times and it doesn't work. also i can't use my set up mic to calibrate any audio settings. If someone can help me out that would be awesome. i am trying to fix this myself and also if someone has a wireing diagram maybe i can use that. HELP!!!!!!!!!

so did you end up getting it fixed or did yo just go ahead and buy a new one?