Issues with iMac display: GPU or LCD screen
User iCare posted in this topic, Re: Issues with iMac screen, how to tell if screen display issues are related to the GPU or to the LCD or flex cable.
Hello everyone! My name is Oswaldo, I am new to this forum, and I hope to find some help here.
So, I have an iMac A1224 (8,1/early 2008) which is having issues with the screen since a week ago. Everytime I press the power button it boots like this:
And after a few minutes it just goes white, nothing else. But if I press the option button to select the hard drive it stays like this:
I already opened it and I see no loose cables or anything. So, what could it be? Should I replace the screen or something else?
User iCare responded:
I suspect that you are having an issue with the graphics processing unit based on the pattern being displayed. One easy way to help determine whether the issue is caused by the LCD or the GPU is to take a screenshot and email it to a computer with a working display. If you see the same issue in the screenshot when viewed on a different computer then the issue is probably with the GPU. If the image looks fine on another computer then the issue is probably with the LCD or less likely, the cable.
Screenshots are a handy tool for troubleshooting. The display is simply relaying the information it is being sent. When you take a screenshot you are simply capturing the contents of the video RAM that is supporting the GPU. If the VRAM is bad, or the GPU is sending corrupted image data to the VRAM then that corrupted information will be captured in the screenshot. After many years helping family and friends with their issues I've found it much easier and safer to isolate the issue using simple methods like this before tearing into the hardware.
Thank you very much iCare, I took a screenshot and it looks fine on my windows computer, so the GPU is working just fine. I still don't know if the issue lies on the LCD screen or the flex cable, so I'll try the flex cable first since it is much cheaper.
This user tip was generated from iCare's contribution to the following discussion: Issues with iMac screen