It started Sunday night, the screen on my 2011 iMac 3.4 ghtz went dark. There was light on the edges of the screen. Restart produced the same result. Reset NVRAM and it started up and worked. My elation was quickly ended the next day when the same thing happened and this time the NVRAM reset gave me a black screen with vertical lines and then dark again. Restart with hardware test and the extended version showed nothing wrong. Restart into recovery mode and it seemed to fix it, yea. That was until just now. Once again the screen went dark and I'm at a loss as to what the heck it wrong. RAM? SSD? Video card? Any ideas?