TV Wont power on!

Hello, i have a Samsung model UN46ES6003FXZA, S/N Z67G3CVCA02640X. The standby light blinks once when plugged in but will not turn on, it normally stays solid. when unplugged it blinks once after 30 seconds. the funny thing is it sometimes works after a period of being off but i have to keep the tv on otherwise it reverts to problem. any ideas and if it is power supply is it worth fixing other then the problem tv is immaculate.