Display turn Black, after many times turn off and on, sometimes works

"I've never seen a power cord go bad like that, but since it's the easiest thing to try, you may as well try another one. Another thing to check would be if the display appears on the iMac when plugged in. Last time I looked at one of these it was rather hard to tell that there was a display when using a flashlight on it until I started moving the mouse around. I realized that the Mac was detecting the display and outputting an image but the backlight wasn't working. This particular monitor would slightly flicker when plugging it into the Mac.

If you're absolutely certain there's no powering on, then it may be the power supply. Here's a link to the Apple Technician Guide for this model."

I don't know if this comment will help anyone, but not sure where to post my "epiphany". My 30" inch Apple Cinema display after having been turned on for a while would suddenly turn off for several second and then back on. It would do this continuously, really frustrating trying to get some work done. As it turned out, this problem was the monitor getting hot, I clipped a simple 6" fan (from Target) to my desk blowing across the back of the monitor, monitor stayed cool and it solved the problem. Hope this helps someone.