After reading many good reviews and finding one cheap $60, i recently purchased a used Onkyo tx-sr600 receiver for a basic home theatre set up. I'm having a problem getting it to produce sound. It turns on and displays correctly. All functions/buttons seem to work. Is this common or something that anyone has heard of? I'm capable of soldering in new components and have a basic understanding of electronics. I've read about an audio protection circuit possibly being activated but do not know how to confirm this. HELP!