Original post by: Steve White ,
You said it is not the power supply. Does that mean you have taken the back off? Is the power supply built in or is it external, like a tablet 19 volt transformer? If you have opened the TV unit, can you identify a relay that clicks as it powers on? If so, as it powers on, hold a small rare earth magnet near the relay. BE CAREFUL not to touch anything, let the magnet stick to anything, hold it near any integrated circuit chips, etc. Sometimes the coil inside the relay gets weak. Holding a magnet NEAR the relay, (but not touching anything) can boost the magnetic field which operates the relay, allowing the contactor inside the relay to close (make connection) and the unit will remain on even after the magnet is taken away. If that works, the relay is bad.