Chosen Solution
Hi, I wonder if you can help me. I have a iMac 2011 21.5" and I have recently replaced the thermal paste on the CPU & GPU as it needed to be replaced. All of the cables are attached properly as the 4 LED lights on the logic board are green when the iMac powers on. The only problem is the screen is black and even when the computer chimes the screen never turns on, BUT the 4th LED on the logic board is green indicating the screen is connected properly. What can I do? What does it mean? Thanks Update (03/23/2021) Here is my GPU I can see a tiny amount of thermal paste in-between some of the SMD devises. Does it need to be isopropyl alcohol to clean effectively the GPU as don’t have that in stock?.
What happens when you shine a flashlight into the screen? Place the flashlight on the glass at a sharp angle, you should see the faint image of your desktop and its icons. If you do they your backlight logic need repairs which is why your onboard diagnostic LED’s are all lit as the backlight is not monitored by the onboard diagnostics. Update (03/22/2021) You’ll need to open the system up and pull the GPU board off to clean the thermal paste off. You’ve either over done the paste so now the SMD devices on the chip carrier has paste on them or you have a bad board.
I’ve marked a few of the small SMD devices that often get covered with TIM which can cause issues.
