Sounds like a short somewhere. I have had this happen on other models from a shorted Fan, a burned Power Regulator, a Failed Power control board, and a bad Power Jack where the AC Adapter plugs in. The first 3 were easily fixed by replacing the bad part, but the last needs the services of a tech who has Surface Mount Soldering Tools to solder on a new Power Jack. The only other thing I can think of is someone somehow spilled liquid on it. If so, new m'board time!!