My wife and I were watching a dvd the other night through our Onkyo TX-DS989, and all of a sudden we heard a pop out of one of the surround back speakers, and since there is a constant loud hum coming out of it. I've tried to hook other speakers into that line, but they just give off the same hum. Common sense tells me that the channel is blown and I need to take it in, and I know this is probably an obvious question, but I thought I'd see if maybe there is anything I could do here before I take the time to unhook everything and send it in to get fixed. Any advise would be appreciated! Thanks!