Television. I have a sony television (not flat screen, lcd, plasma) just a regular tv...that the

Question

I have a sony television (not flat screen, lcd, plasma) just a regular tv...that the picture keeps blinking on and off. the sound stays constant, just the picture is affected. the longer the tv is on the longer it is between blinks..the picture stays for not more than 30-45 seconds each time. when you first turn it on it blinks every 2-3 seconds.

help