Why Does my display go dark after 15-30 minutes?

When powering the iMac on after being turned off for awhile the computer boots normally but after 15 to 30 minutes the display goes dark and does not recover unless the iMac is unplugged for a while or if I put the iMac into sleep for a few seconds then wake it up the display recovers and quickly clicks off.

If I unplug the iMac and power it back immediately on the display will shut of as the computer boots.

When I hold a flashlight up to the display you are able to make out whats on the screen and do things as normal I tried moving mouse around as well as playing audio through the speakers.

I believe this is a problem with the inverter are there any other suspects?