Monitor displays banding, external monitor displays good image
I left my iMac for a moment and came back to a screen showing horizontal banding and distortion. I tried running diagnostic tests but they didn’t show that anything was defective. Just to be curious, I attached an external monitor to the computer through mini display port. The content on that monitor is fine. So, is the issue likely with the internal display, the graphics processor, or a bad connection? If it is an issue with a connector, then I can fix that. However, a bad display or processor are different stories. I am not going to sink money into a repair that I cannot afford right now.