Hitachi I have an Hitachi 43FDX20B HD TV monitor. When the TV is turned on and plays for a little while it turns off on it's and the red indicator light continues to blink

It will turn on fine. Picture is fine, after awhile it just goes black and begins blinking the power light on and off. The picture, when you turn it on nomrally makes kind of a frequency sound, well when its blinking on and off, it makes that sound as well. Its a high pitch switching frequency sound. I simply hit it on the top and it turns back on for awhile. Had the convergence replaced already, its not the issue. It will turn on fine. Picture is fine, after awhile it just goes black and begins blinking the power light on and off. The picture, when you turn it on nomrally makes kind of a frequency sound, well when its blinking on and off, it makes that sound as well. Its a high pitch switching frequency sound. I simply hit it on the top and it turns back on for awhile. Had the convergence replaced already, its not the issue.