Just a quick note for others who may be having similar problem. My TC-P50S30, manufactured the end of 2011, put in service 1/2012, started having a buzzing noise from the upper right corner of the set when viewed from the rear, varying with screen brightness/whiteness. Plasmas as a whole have some buzzing associated with them, but this is clearly not normal and was new. After lots of Google research, I have determined that the noise on 2010 sets is usually due to a cracked transformer ferrite and has been cured by wrapping the transformer with zip ties to act like a clamp. Google it on your own if you want more details. However, for sets made in 2011, the cause is loose screws on the boards, very commonly the board near the upper right corner as viewed from the rear. The screws themselves don't vibrate, they act as a ground path for the boards and when not tight lose their conductivity. After removing the rear panel, I found one screw, the usual one implicated, able to be tightened easily about a 1/4 turn. This eliminated the buzz right away. Several others were slightly loose on other boards. I tightened them all up. Note, Panasonic makes a replacement screw kit for this reason. The new screws have split type lock washers on them. If my screws loosen up again, I may go for the new screw set, or maybe blue loctite instead. Hope this helps others.