iMac won't wake up from sleep using keyboard or mouse

Just to bump one of my previous posts. It turned out in my case to be a faulty backlight board. I had it replaced and now the problem has gone away (so far).

Symptoms:
Computer would not fully wake from sleep, all components would be awake but the screen would be dark. Had to toggle sleep mode: ctrl-shift-eject to get the backlight to come on

Solution:
Had backlight board replaced

Hi am working in Apple Repair Centre and I end up in this forum. Can you believe? Same problem with customer's iMac (21.5-inch, Late 2009):

Goes to sleep and then using mouse or keyboard (wired) comes back with image but no backlight at all. According to Service Manual I have reseated all possible cables antried again - same fault. Then I have replaced Backlight Board - same. Replaced LVDS Cable (LCD to Logic Board) - same. Finally I have replaced LCD Panel. So with 3 new parts computer started to work fine. eventually after two hours of testing and browsing web, screen saver applied. guess what? Yes - I click keyboard button to wake it up and image appeared but no backlight

Normally this fault is connected to the Backlight Board, well that's what most of the people say when they have had an apple repair on this fault, "backlight board replaced and fault has not recurred".

In your case mroczek82 all i can think of is the logic board! Ouch!! unless you are so unlucky to have 2 faulty backlight boards?

Pedro3178, there is last thing I want check before ordering Logic Board - install new MAC OS on another partition and check again. According to service Manual is very unlikely to be OS but I have to try. One more thing - I have observed that when decreasing brightness using F2 key - I cannot actually decrease is dramatically but just about half... I mean progress bar goes maximum left but you can see eveything on screen almost without problems.

Tried to install MAC OS X from USB HDD and got Kernel Panic... nice.

hi,

Using the brightness key will increase or decrease the intensity of the brightness but wont 100% blackout, i highly doubt it to be OS but you are correct to try everything other than to just replace the logic board.

Did you try a SMC,NVRAM reset after fitting new board? just a thought

Reset done on both.

I can't think of anything else, if i had another spare backlight board and not a logic board then i would try another backlight board before ordering a logic board just incase.

Be good to know how you get on!

I have wasted enough time so far. I cant keep ordering all 3 parts just in case all of them were DOA (Dead/Faulty On Arrival). I am going for Logic Board. I will update you tomorrow.

Add me to the list. Just bought my 27" i3 Imac this past January and having the same problem. Pressing buttons on the keyboard or clicking the tracking pad, nothing, does not wake up. Even pressing the power button does not even wake it up. I didn't want to pay close to $2000 for a desktop to function this way. I'm sick of holding down the power button to restart the system. Anybody found a solution yet?

Hi deagle0904

Can i just ask you if this has just started happening? what i mean is if you always allowed your iMac to sleep without problems and this has just started happening then it must be a hardware related fault. In most cases the backlight board replacement fixes the issue. Did you take out apple care? oh! you just bought it january? just contact apple for exchange...

My iMac started to experience the display problem several months ago. The display would not wake from sleep. I set the computer to go to sleep with the power button. I press the power button to put the computer to sleep and then wait 20 seconds. Then I press any key on my wired keyboard and the display works fine. I am using time machine with the iBook HD. I have a wireless mouse.

When the screen is dark, I can use vnc for screen sharing to connect to my computer from another computer and see that the computer is awake and functioning normally. It just seems that the LED backlight is failing to start properly. So far, I've corrected the permissions and verified the disk. No luck yet.

Does this problem get progressively worse?

It just started happening actually. About a week ago. It was an intermittent thing. However, last night it just became persistent. Everytime I put it to sleep (Manually), I cannot wake it up. I must have pressed the power button 20 times just to reboot. I tried everything, from resetting the PRAM and SMC to disk repair under disk utilities, to removing the both the wireless keyboard and trackpad from bluetooth and reinstalling again, etc. The one thing that was strange was that I rebooted to Safe Mode and for some reason, I would be able to wake it up from sleep manually and when set on energy conservation(5 min). I did that a few times and it was working flawlessly. I know I have one year warranty from apple, it's just I don't feel like lugging that 27" imac back to apple when it just might probably be a software issue(bluetooth maybe?) However, if it has to go back to apple, then so be it. I know apple sees this as an ongoing issue and hopefully a fix is within reach. Like I said, paying close to $2000 for a desktop to run like this is up surd.

Logic Board replaced - same.................... only power button wakes iMac. Power Supply perhaps? Somebody please WAKE ME UP!

Sorry to hear that!, i can't see it being the PSU as when you boot the machine it will work fine? if so then the PSU is ok, some how putting the machine to sleep then trying to wake, power is not being sent to the backlight board, or its not being told to turn back on if you see what a mean? Not having the machine in front of me its really hard to diagnose, its also not the easiest machine to check with a meter when its working and when its not, that way you can be sure if power is there or not! if you don't activate sleep does the machine just work away as normal??