I have an older yamaha rx-v850 receiver that has decided to give me trouble, the Left channel will cut almost completely out to the point where you can kind of hear garbled up sound at high volumes. It has never done this before yesterday, but I gave it a tap on the lid and it came back in and sounded fine, any ideas? I checked all connections on the back and they are fine, this morning it cut out again for about 2 sec, then came back on again fine.......wierd. I wondered if I was to get some contact cleaner and spray out the potentiometers and switches, but when the sound cuts out, there is no control, switch or anything that you can mess with to get it back on, you basically have to tap the top of the unit a few times it seems to get the sound back. Any help anyone could give me is greatly appreciated.... the old yamaha was a nicer unit a bunch of years back and sounds so good when it works I hate to replace it. thanks!

Brandon