SONY STR-DE1075 Protection error
So I got a used SONY STR-DE1075 to replace my Yamaha HTR-5730 that recently died. Everything seemed fine at first, but I noticed my front left speaker had some constant static sound. I figured it was a loose speaker wire, nope... replaced speaker wire... nope.
THen, I went to slide the receiver over to get back to the wires and that ever so slight tap on side made that speaker cut out and in. TINY tap, almost more of a touch. I figured out if I tap on side repeatedly it eventually works perfect... for a bit. I took the top off and lightly tapped around inside with a precision non-metalic tool (plastic mechanical pencil). I determined that the only place that affects anything is the MAIN board. Again, more of a touch and it will cut in and out repeatedly til it either clears up or pops and goes into Protect mode.
I took the bottom panel off and don't see any visible cold solder joints/cracks. Basically, if I touch anything on that board with unit on it sounds like tapping on a microphone and that tap is heard through the speaker, but only that front left. Also note, it does not do that when doing anything with the smaller board for the wire terminals or anything there. It is just the MAIN circuit board. Any ideas as to what components to look at more closely or suspect as a cold solder joint to fix? I do like this receiver and would like to fix rather than try to get a refund if it is something as simple as busting out the soldering iron quick (but not so much if the only solution is buying a replacement MAIN board).