Chosen Solution
I have a 27” iMac Mid 2010 Core i7 2.93 GHz that has run well for many years. Starting about 6 months ago the screen would go blank randomly. Putting the Mac to sleep and waking it up would bring the screen back. It important to note that only the back light would go out. I could see the screen image with a very bright light and the external Apple monitor was unaffected. Over time it would happen more often and I noticed that lowering the brightness would allow the screen to stay on. I got to where the brightness can not go above 2 notches before the screen would black out. I have tried to replace the inverter board (with a new on), the actual display with a use one as well as the Radeon HD 5750 graphics card with a used one. None of these have helped. I have read every thread and each has had different solutions. I’m not sure what to try next. Any thoughts?
The only thing I can think of that could be a factor here is the SMC logic within the main logic board. I would run the onboard diagnostics to see if something pop’s. To run diagnostics reboot your system and press the D key to enter. Let us know if you get any errors. I would also look at the thermals using a good monitoring app like TG Pro if you get the full version you can get logging which might help in identifying whats happening here.
dasgeek “lowering the brightness would allow the screen to stay on” and since you’ve already changed your LED driver board, changing your backlight strips should fix this issue.
