Probably a capacitor is damaged somewhere on the power supply. Send it to a shop to fix it or DIY. Be careful on DIY because the crt screen can store a lot of static. Make sure you unplug tv and hold power button. Open case without touching things inside, then use two well insulated screw driver, one touch the back of the crt, one touch a ground source (metal frame) and bring the metal rod part of the screw driver together (usually result in a big spark when discharge), then change all capacitor on the circuit board closest to the power cord.