philips crt TV screen going off after power ON

my philips crt tv screen going off when power on. it will remain only about 4 seconds and suddenly going off.. but power supply remain on position.. plz help me.. thank you

Check the ultor cap to the top of the tube, do you hear the whistling after switching on ? You may have partial discharge on it and overloading the flyback transformer. Check all high voltage wiring as well.
Ensure the TV is unplugged from the mains, and discharge the ultor cap terminal to screen aquadag earth wire before touching carefully by inserting a small screwdriver with earth lead underneath the rubber dustcap.