We've been seeing a lot of Vizio M550SV Smart LED TVs with problems of no sound, no audio on any input. These are good sets and were made in 2011 and 2012. The problem is on the audio section of the main board. There are 5 components on the board that need to be replaced for this repair to last. Replacing the whole main board will get the sound back on but the TV will end up having the same problem down the line AND replacing the board is about $200 more expensive than repairing it. This is usually a same day or next day repair.