Had this TV for 4 years with no problem other than replacing the bulb a few months ago. The other day a black spot appeared on the right side of the the size of a baseball. It's not completly black as you can kinda make out the picture through the spot if the image is fairly bright. Does anyone know what this might be? I've read somewhere that this kinda thing may be dust but not sure how to clean that off if it is. Any advice would be greatly appreciated.


















