Had the same issue with 2012 model. Have a background in electronics so decided to have a look in the back (no test equipment). Noticed some discolouring around 2 pins on the power supply board that feeds the main processor board. Closer inspection showed that the plastic insulation between the pins had melted and they were shorting out (hence the continued on and off cycle). Cleaned the pins, used some silica set to insulate the pins, cleaned them and put panel back together. All working and keeping and eye on it re over heating.