Intel iMac Black screen on wake up from sleep

Hi, has anyone come across this? My imac intel 20" running 10.4.11 now routinely presents me with a black screen on waking up from sleep. The computer still seems to run as normal, the mail application beeps when new mail is received but the screen is black. I have to switch off the computer, reboot and do a NVRAM reset, sometimes up to 8 times in order to get a functioning screen. The beautiful Lexus has turned into a 10 year old Ford Escort; i think -not sure though- that this started with the latest system update. All advice greatly appreciated. Jan

I, too, have this problem. I don't have a cure but I do have a workaround.
If you close the lid again and watch the light on the front it will be solid on. Keep the lid closed and keep waiting (which might take a minute or two) and eventually the light will start "breathing". Now you can open the lid and your computer should be up and running normally.
Although waiting for the light to start breathing is a pain (especially if you're pressed for time) it's still quicker and safer than shutting down and restarting.
Bob

Similar Messages

Beach ball on black screen when waking Mini from sleep

I am looking for a way to fix this frequent problem. About 25% of the time I wake this 2-year-old Mac Mini from sleep, it will show a spinning beach ball or a regular pointer on a totally black screen. The monitor connected is an Acer, by the way, and it's had multiple color calibrations done to it... Anyways, the pointer or beach ball doesn't go away if you just let it sit awhile, but it does move with mouse motion. So the only ways of getting to the login screen from there are:
hold down the power button on the computer for 10 seconds, then start it up as usual.
unplug the HDMI cord that connects to the display from the back of the computer.
What does not work:
unplug the HDMI from the back of the display
turn the monitor off and on
unplug and replug the monitor
pressing keyboard shortcuts to shutdown, reboot, sleep, etc. don't work.
So from this I've deduced that it has something to do with the Mac Mini recognizing the Acer display and having to refresh that port's connection.
What I've already tried that has not permanently fixed the problem:
Reset the PRAM
Having frequent power outages counts as resetting the SMC, right?
restarting the computer (duh)
Doing the Apple Diagnostic test
Had Disk Utility test the hard drive (well ok its an ssd) and found no problems with it.
Help! It's not so much a problem for me but one other person who uses this computer is computer illiterate and cannot do a hard reset or figure out which cable goes where. And please, please, please do not take the easy way out and tell me to reinstall OSX (it's mavericks by the way). Thank you very much.

Humm... May have something to do with the straight HDMI connection, others have also complained about similar problems using a straight HDMI connection.
1. You tried a different HDMI cable...? (you didn't say)
2. What model is your Acer and what other inputs (DVI, VGA, etc.) does it support...?
I run dual DVI Samsung monitors on my Mac Mini and have not experience any problems. One is on the Apple Supplied HDMI to DVI adapter and the other in on a Kanex Mini DisplayPort to DVI adapter.
No a power outage does not equal an SMC reset. If fact, it can have just the opposite effect and throw the System Management Controller off kilter.

Blank/Black screen after waking up from sleep mode

Hi there,
So this is my first time using a macbook. I purchased a macbook pro with retina display in August of this year. I have never had this problem but after i have updated to the new Yosemite OS, my problem keeps happening. I will be using my computer to work on assignments. After, ill put my mac to sleep and close the lid screen. When i come back and turn it on, it shows a bank/black screen. The keyboard lights up but nothing shows on the screen. So i end up close my mac and reopening it again and it still is blank screen. After a few tries opening and closing, i type my login password even when the screen is black. After, i close it again and reopen it and now my screen shows my background and login information. I enter the password and it works fine. I'm not sure if this a problem that needs to be looked at? I have taken care of my computer since day 1 so im not sure why this problem is happening. Any help/input would be greatly appreciated. Thank you

Hi ellaine,
Lets check your energy saver settings:
About Energy Saver sleep and idle modes in Mac OS X
http://support.apple.com/kb/HT2412
Regarding your second question, it may be that your display is set to sleep before the screen saver starts. That would cause the screen saver to never display.
Thanks,
Matt M.

Black Screen after start KDE from sleep mode

Hai everyone,
i just press sleep in start menu in KDE, but when i start again i can't see prompt password and i just see black screen.
please help me.
Sorry for my bad English, because English not my native language.
thank you.

i think its being discussed in here
https://bbs.archlinux.org/viewtopic.php?id=159379

X121e - Black screen after wake up from suspend to RAM

I am the owner of a ThinkPad X121e - Notebook Type 3051-5QG (AMD E350 Processor). After a BIOS - Update from 1.07 to 1.16 I have a problem to wake it up from the S3 - Suspend to RAM function.
The Notebook restarts and the fan is working but there is no beep and the screen stays black. There is no way to get it working except a complete hard shutdown pushing the on/off-Button.
Does anybody know the problem and has a solution? Or do I have to wait and hope for the next BIOS-Version to solve the problem? I would like to downgrade to 1.07 BIOS, but I am afraid that this is not possible.
Solved!
Go to Solution.

Since 2012-12-02 Lenovo has published an new Bios-Version 1.17 .
I installed the update today and the problem is gone. I hope there is no new bug in this Bios-Version, but up to now everything seems to work properly.

Found: Intel Turbo Memory causing T61 wake-up from sleep / standby problems

This is related to my earlier post, but I've found a new cause and thought to post a new message to make it easier for others to find it if they are running into similar problems.
My system
T61 model 7662-CTO (built July 2007)
Vista Business w/ SP1
Nvidia Quadro NVS 140M (driver version: 7.15.11.7597)
Intel Turbo Memory (driver version: 1.7.0.1029)
Intel Wireless card 4965AGN (driver version: 11.5.0.36)
Thinkpad BIOS (version 7LETC4WW, 2.24)
no card reader or integrated webcam
I was having problems with Vista failing to wake-up after being put into sleep (or standby) mode. Instead of returning to the desktop, the system immediately crashes and reboots. After many hours, I reformatted the drive and re-installed Vista (business edition). Before running the Lenovo system update, I installed Vista Service Pack 1, then I ran Windows Update and installed any remaining update hotfixes. (I never delayed restarting the machine when prompted)
I incrementally began installing Lenovo drivers, and after the Power Management driver determined that hibernate was working.
The 'sleep' option was unavailable until I installed the Nvidia Quadro NVS 140M drivers. Then sleep worked!
Note: Intel Turbo Memory driver was uninstalled at this time.
After all other lenovo programs were installed, I installed the driver for the Intel Turbo Memory. I put the computer to sleep, and it crashed/rebooted upon being woken up.
I uninstalled the Turbo Memory driver from the Device Manager, and normal sleep -> wakeup function resumed.
Because the sleep / standby feature requires the Nvidia Quadro drivers, and the Vista OS and the Intel Turbo Memory must properly work together for the turbo memory to work, I imagine the failure involves some driver mismatch between these three. I cannot recall now whether this issue was present when I first received the machine over a year ago (pre-installed Vista Ultimate, service pack 1 not even out yet). Perhaps Vista SP1 made some change that the Turbo Memory driver doesn't like, particularly with the Nvidia Quadro drivers in the mix too.
Just FYI for anyone interested or curious.

Remove the two aftermarket memory modules and observe the results.

Imac mid2010 doesn't wake up from sleep

Hello to everybody,
i've read all of topics speak about this problem but i haven't solved. When I press space button or push something else the mac reprise to move the fans but the monitor doesn't power on. One arouse curiosity: is if try to wake up before the fans go to stop the monitor wake up immediatly, but if I wait for 20 second or somenthing more after the fans gone to sleep, the mac keep black on wake up. I tried to reset PRam and fix permession, tried to format the harddisk and install new maverick, also tried via recovery but nothing changed.
This is part of consolle's report and I thing is the reason about the problem of wake up. It appears after every sleep time:
powerd[29]: com.apple.message.domain: com.apple.sleep.failure
com.apple.message.signature: Platform Failure
com.apple.message.summarize: YES
Sender_Mach_UUID: 83C854AA-0FB9-30C2-8443-D10D781E0E25
I hope that someone can give me some information about this problem,
Waiting for your opinion....thank you in advice!!

Sleep - Wakeup

10.4.8 - Wake-up from sleep issue: Workaround

I eventually got rid of wake up from sleep issues on my PB G4, which I had systematically experienced since I upgraded to 10.4.8.
Here is a workaround for those who have customized their EnergySaver:
- the display and the computer must not go idle at the same time ; just select different timeouts.
For those whom it may help.
MacBook Pro - PowerBook G4 - iBook G3 - iBook G4 - iMac G3 Mac OS X (10.4.8)

Actually, another workaround seems to work much better when my PB's display a black screen after wake-up from sleep :
- close the lid
- wait for a few seconds
- re-open the lid.

TS1367 I am asking this question about my 27 inch iMac Desktop Computer. I normally use my Laptop and very seldom use the desktop but was going to download the new software earlier today. I could not wake it from sleep.

The other evening we had a storm and lightening hit a house a few doors from me. It jolted my chair but that seemed to be all here. I use my laptop most of the time but since there was a software download I went to my 27 inch iMac and could not wake it from sleep. The light on the keyboard is not lit either. I have this connected to a Battery Backup Power so do not know what has happened or what to do. When I push the power button to try to turn it on nothing happens. There is no shound, no video, nothing; however the disk drive that does my time maching backup has a light on it and the other things that are plugged into the battery power pack also have lights on them. The printer is on and says it is ready to print. Since I cannot boot it up I do not know what to do to even try to get it started. I did not know what would happen if I put the first start up disk in the external disk drive and try that or not. The internal drive is broken. I do not have any repair shops or apple stores around me at all less than 150 miles away and I am disabled with 24/7 help and oxygen so can not take it in. Are there any suggestions that anyone can give me. I have not been able to find any way to reset the backup battery pack either. It is a Tripp-Lite. Any help anyone can give will be greatly appreciated. Thanking you in advance for your time and trouble.
Jean

The other evening we had a storm and lightening hit a house a few doors from me. It jolted my chair but that seemed to be all here. I use my laptop most of the time but since there was a software download I went to my 27 inch iMac and could not wake it from sleep. The light on the keyboard is not lit either. I have this connected to a Battery Backup Power so do not know what has happened or what to do. When I push the power button to try to turn it on nothing happens. There is no shound, no video, nothing; however the disk drive that does my time maching backup has a light on it and the other things that are plugged into the battery power pack also have lights on them. The printer is on and says it is ready to print. Since I cannot boot it up I do not know what to do to even try to get it started. I did not know what would happen if I put the first start up disk in the external disk drive and try that or not. The internal drive is broken. I do not have any repair shops or apple stores around me at all less than 150 miles away and I am disabled with 24/7 help and oxygen so can not take it in. Are there any suggestions that anyone can give me. I have not been able to find any way to reset the backup battery pack either. It is a Tripp-Lite. Any help anyone can give will be greatly appreciated. Thanking you in advance for your time and trouble.
Jean

Imac 20" intel Leopard black screen, does not start up

Imac 20" intel Leopard black screen, does not start up,
yestarday i put my imac aluminium in sleep, when i wake up this morning the computer did not start up from sleep and also did not start up from the power button back, i try several times and nothing, i hear the sound of the start up but i remain with a black screen. What can be the cause? The video , maybe? I did not install any hardware lately on it.
note: i have a wireless keyboard & mouse
Message was edited by: mindsoul

Not running Leopard (Panther), but I have a similar problem on my 24" iMac. Computer was working fine last night (I shut it down) and when I went to boot up this morning the computer is stuck on a black screen.
The boot up sound is initiated but nothing after that. The power light stays at full brightness, if I touch the power button the light blinks and then after a while it goes out. A full reset does nothing. I've tried reseting my PRAM, which works because I hear the start up sound twice, but no change to the black screen.
I don't have access to another Mac, would inserting the Startup Disc I received with the computer do anything?

I have a late 2006 iMac that has just started giving me a message to reboot after a black screen comes down slowly from the top top of the screen to the bottom. I reloaded software and restored from Time Machine, it now happens frequently. Any insight?

I have a late 2006 iMac that has just started giving me a message to reboot after a black screen comes down slowly from the top top of the screen to the bottom. I reloaded software and restored from Time Machine, but it keeps happening, now several tomes a day. Any insight as to the issue or a proposed solution?

Unplug any peripherals you have except your keyboard, reboot, and check activity monitor for apps. Keep running apps to a minimum to find the App causing the issue.

Guide to Upgrading to Windows 8 on the T540p (+fix for brightness/black screen on wake)

Hello all. I recently received my new T540p running Windows 7. Although I probably would have qualified for receiving Windows 8 recovery media from Lenovo, I went ahead and did the upgrade myself since I had a copy of Windows 8 laying around (and because I'm impatient). I'm fairly tech-savvy and expected the process to go smoothly; boy was I wrong. I decided to write up this little guide after having a thoroughly annoying time upgrading in the hopes of saving someone else out there from the hassles I underwent.
NOTE: The most troublesome part of the whole process was figuring out why the screen brightness was no longer adjustable and the display would not turn on after waking from sleep (black screen) after upgrading to Windows 8. Skip ahead to step #9 if that's the issue you're having.
Step #1: Make a bootable recovery disc or USB drive
This is important in case anything goes wrong during the upgrade or you decide you despise Windows 8 and want to bring back Windows 7. The T540p comes with a recovery partition in the hard drive (like most laptops nowadays I assume) which allows you to completely wipe your computer and reset it to its original factory state (the same as when you first received your computer). This is normally done by restarting your computer and hitting the enter key to interrupt normal startup and selecting the recovery option from a menu. I wrongly assumed that I would still be able to conduct the recovery after installing Windows 8, but for some reason after upgrading I was unable to start a recovery from the recovery partition. Thus it's important to create a set of recovery discs or a recovery USB drive yourself BEFORE starting the upgrade. Lenovo includes a program which makes this step very easy; see this page for details: http://support.lenovo.com/us/en/documents/ht004960
Step #2: Uninstall certain programs BEFORE upgrading
I skipped this step because I forgot about it. I haven't noticed anything adverse (aside from the brightness/display problem which I assume is completely unrelated), but Lenovo does suggest to uninstall certain programs before upgrading so it's probably wise to do so. Here's the list:
    - DisplayLink Core Software
    - Intel(R) USB 3.0 eXtensible Host Controller Driver
    - Lenovo Solution Center
    - RapidBoot
    - ThinkPad(R) Bluetooth with Enhanced Data Rate Software
See this page for details: http://download.lenovo.com/lenovo/content/windows8/upgrade/think/notebook2_en.html
Step #3: Download and save wireless drivers to external media BEFORE upgrading
After upgrading, I discovered my wireless didn't work and thus I couldn't connect to the internet. I wound up downloading the wireless driver to my phone and transferring it to my T540p. You could also use an ethernet cable to connect to your wireless router or cable modem. But if you have a USB drive, CD, DVD, external hard drive, whatever, save yourself the hassle and download the wireless driver ahead of time. You will need to know the brand of the wireless device (Intel or Realtek); look it up in your email receipt or from the Windows Device Manager under "Network Adapters". Mine was Intel. After figuring out the brand of your wireless device, go to the T540p drivers page here: http://support.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-t-series-laptops/thinkpad-t54... Look for a drop-down menu that says "Component" and select the option "Networking: Wireless LAN" (LAN, not WAN!). The page will refresh to show only the wireless drivers. Select the Windows 8 64-bit driver that matches your brand (I'm assuming all T540p laptops are 64-bit. If I'm wrong, please correct me). Download that sucker and put it to on the external media of your choice to use later!
Step #4: Begin Windows 8 upgrade
You'll obviously need to have a valid Windows 8 key or purchase a copy of Windows 8 for this step. I had a valid Windows 8 key that had been used on an old computer which died (hence my new Lenovo), so I reused it. This requires Windows 8 to be activated by phone which isn't nearly as scary as it sounds. We'll get to that later.
There are two ways to do upgrade: use a Windows 8 installation DVD or download a web installer. I had a Windows 8 key from a previous web installation and went with downloading a web installer. If you have an installation DVD, just insert it and get started. If you prefer to download a web installer, go to this page: http://windows.microsoft.com/en-us/windows-8/upgrade-product-key-only I think product keys are tied to either Windows 8 or Windows 8.1, so select the one that you have a key for and download the appropriate one. If you're not sure, you may have to try both.
During the upgrade, you will be asked whether you want to download updates (I assume this updates the installer) and afterward you will be asked to enter your product key. For some reason, when I downloaded the updates my product key would get rejected. I just restarted the Windows 8 installation, skipped the updates and then my product key was accepted. I don't know if this is tied to the fact that I was reusing a Windows 8 key (again, which had been used on a now dead computer) but if you find your key getting rejected then you may find skipping the updates helps. If this doesn't work and you're using the web installer, try downloading the other web installer (e.g. if you're using the Windows 8.1 web installer and find the key is rejected even after skipping updates, your key may actually be for Windows 8 and you should try downloading the Windows 8 web installer).
The installation itself should be a fairly straight-forward process. There are lots of guides online in case things go awry. If you have any trouble or errors, you should hopefully have made recovery media for worst case scenarios where you need to start from scratch.
Step #5: Install wireless driver & connect to your router
You should now have Windows 8 up and running on your system, but no wireless. Now's the time to use that driver you downloaded earlier. Install it and you should now have wireless access. Connect to your router and get online so we can start some badly needed updating!
NOTE1: your touchpad/trackpoint/keyboard experience will be especially funky at this point. That's because the drivers for them haven't been installed. Normally the touchpad won't be active while you're typing, but because the drivers haven't been installed you'll notice you'll accidentally move the mouse or click while typing (e.g. when entering passwords). Not to worry: this will go away when we install the Lenovo drivers now.
NOTE2: your function keys won't work (adjust sound, adjust brightness, etc.). That's also because of the drivers.
NOTE3: you may notice your screen's brightness may not be adjustable even from the Windows menu. Again, that's also because of the drivers. Hang in there!
Step #6: Activate Windows
Now that we're connected to the interwebs, it's time to activate Windows. If you're completely new to Windows 8, here's where you go:
-move your mouse to the upper right corner then move down
-select "Settings"
-select "Change PC settings" at the bottom
-select "Activate Windows"
This is where you'll enter your product key. As I've said before, my product key had already been used on an old, now dead, laptop. Reusing a key requires you to do a phone activation. If you find your product key gets rejected, go to the phone activation option and follow the instructions. An important note: at some point you will probably be asked how many devices/computers you installed Windows on. The correct answer is "one"; if you accidentally give another number, you'll need to call again and start over. (I'm assuming you're not doing anything illegal. As far as I know, there's nothing wrong with you reusing your key so long as you're no longer using the old computer Windows 8 was installed on, e.g. when that old computer no longer works. But if you're trying to install Windows 8 on multiple computers and you can afford to buy a new copy of Windows 8, shame on you. It takes a huge team of coders and support staff to make a product like Windows happen; help them pay their bills by purchasing a legal copy of Windows 8. Students can even get a copy for less than $70 with proof of student status. http://www.microsoftstore.com/store/msusa/en_US/pdp/Windows-8.1-Pro-for-Students/productID.288769600...
Step #7: Install Lenovo-specific updates and drivers
I typically hate all the crapware and bloatware companies include with new laptops, but Lenovo does make some which are useful. Their system updater should take care of downloading the rest of the drivers you'll need instead of having to download them all individually (with one exception: the graphics drivers may require a separate download later). Download the system updater here and keep running it until there are no more updates to download: http://support.lenovo.com/en/documents/ht080136
Step #8: Install Windows Updates
Load up Windows Update and start installing. If you're completely new to Windows 8:
-move your mouse to the upper right corner then move down
-select "Settings"
-select "Change PC settings" at the bottom
-select "Update and recovery"
-click the "Check now" button to check for updates
-click the "View details" text link to see the available updates
-click the "Install now" button to begin installing immediately
(Yes, the Windows 8 interface is dreadfully unintuitive unfortunately. Watch some Windows 8 tutorials on YouTube if you find yourself having trouble. Already looking forward to the next version of Windows!)
You'll also want to download the Windows 8.1 update if you installed only Windows 8 (the update to 8.1 is free). The download is available from the Windows Store.
Step #9: Install graphics drivers (if you're having display problems: unadjustable brightness, black screen on wake from sleep)
As I stated earlier, this was the most frustrating part of the installation process. My T540p came with only an Intel HD Graphics 4600 card, but it seems some others include a dedicated NVIDIA card. Whatever updates were installed with Lenovo's System Updater and via Windows Updates didn't seem to do the trick. I even updated the driver with the latest from the Intel website to no avail.
The solution, at least in my case, was simple: go to the T540p driver's download page and download the graphic card drivers appropriate for your system. Go here: http://support.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-t-series-laptops/thinkpad-t54... Look for the "Component" drop-down menu and select the "Display and Video Graphics" option and download the Intel and/or NVIDIA drivers appropriate for your system. (I have no idea what the Intel Wireless Display driver is for, so I avoided it thinking I don't need it)
BONUS Step: Go to ninite.com to download commonly used programs
Shameless plug for one of my favorite websites. It lets you pick from a list of commonly used programs, then downloads and installs each of them all automatically (and skips all toolbars/extra junk downloads). Makes getting started on a new computer a breeze!

Hello Yolanda,
a) I noticed that I can´t install MediaCenter on Win8, but just on Win8 Pro.
b) My problem is, as described, that installing "MediaCenter" on either "Win8 Pro" or "Win8.1 pro", though the "Media Center" key is accepted,
which I once 2 years ago downloaded on ANOTHER "Windows 8 Pro" computer, for free as it was a gift of Microsoft at that time - You could reserve = get up to 5 Media Center licenses per "Windows 8 Pro" computer for later use
on OTHER "Windows 8 Pro" computers - but never used ( i.e. NEVER USED FOR ACTIVATION ),
but after the first reboot, I am running "Windows 8 Pro with Media Center" WITHOUT LICENSE, as shown in the system screen.
Neither my "Windows Media Center Key" nor my "WIndows 8 Pro key" is then accepted to change the situation - I mean the keys I entered just before during the installation process of "Windows 8 Pro" and "Windows Media Center".
I am shure that I did not use the "Windos Media Center" key, as I have a list of personal keys I got for free from Microsoft, and I marked those 2, I used for other "Windows 8 Pro" computers.
So fact is, that with my brand-new computer, 32 Gigabytes of RAM, 4 Cores, "Win8 Pro" installed, I am forced to avoid the installation of "Windows Media Center", though I got valid licenses.
So your answer was not quiet helpful, as it does not change anything.
Sincerely
Rolf

My imac freezes , need to restart everytime i wake it from sleep mode. just started happening 2 weeks ago.

For about 2 weeks whenever I return to my imac and tap the mouse to wake it from sleep mode my screen is frozen. I have tried to wait for it to unfreeze but it doesnt wake. I cannot get any results from using the mouse or the keyboard. I always have to hard reset the computer to be able to use computer again. My mac is a year old. Anyone have any thoughts as to why tis is happening? Thanks

If you have more than one user account, these instructions must be carried out as an administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
Step 1
Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.
Enter "BOOT_TIME" (without the quotes) in the search box. Note the timestamps of those log messages, which refer to the times when the system was booted. Now clear the search box and scroll back in the log to the last boot time when you had the problem. Post the messages logged before the boot, while the system was unresponsive or was failing to shut down. Please include the BOOT_TIME message at the end of the log extract.
Post the log text, please, not a screenshot. If there are runs of repeated messages, post only one example of each. Don’t post many repetitions of the same message. When posting a log extract, be selective. In most cases, a few dozen lines are more than enough.
Please do not indiscriminately dump thousands of lines from the log into a message.
Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.
Step 2
Still in Console, look under System Diagnostic Reports for crash or panic logs, and post the entire contents of the most recent one, if any. In the interest of privacy, I suggest you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header of the report, if present (it may not be.) Please don’t post shutdownStall, spin, or hang logs — they're very long and not helpful.

IMac G5 iSight will not wake up from sleep

This has been happening to me for some time.
Occasionally my Mac do not wakes up from sleep. Instead it hangs!
Here how it goes:
I press a key on keyboard; my Mac wakes up, but screen remains black with only mouse pointer. I cannot see login window.
And Mac stays this way for hours. No matter if I press a key, click a mouse.
The only remedy is to press power button and to shut it down.
Then I have checked console.log. Nothing spectacular. Here is log from last accident:
Jul 31 21:43:36 snukec kernel[0]: System Sleep
Jul 31 21:43:36 snukec kernel[0]: IOBluetoothHCIController::restartShutdownWL this is a wake from sleep
Jul 31 21:43:36 snukec kernel[0]: System Wake
Jul 31 21:43:36 snukec kernel[0]: Wake event 0020
Jul 31 21:43:36 snukec kernel[0]: USB caused wake event (OHCI)
Jul 31 21:43:37 snukec kernel[0]: FireWire (OHCI) Apple ID 52 built-in: handleSelfIDInt - received quads == 0. issuing bus reset
Jul 31 21:43:38 snukec kernel[0]: UniNEnet::monitorLinkStatus - Link is up at 100 Mbps - Full Duplex
Jul 31 21:43:42 snukec kernel[0]: AFPSleepWakeHandler: waking up
Jul 31 21:43:42 snukec kernel[0]: AFP_TCP ASP_TCP SendSleepPkt: sending ext sleep wakeup
Any idea what to do?
Matej

Wait - before you take it in for repair or get put on hold with Support try this:
Go to System Prefs, Energy Saver, then set your display sleep and computer sleep times the same. Check both check boxes too.
Trust me, I've been working on this problem with Apple and checking the discussion boards for over a year now. I've had my logic board replaced, power supply replaced, been through about 8 Apple techs and tried just about anything you'll read on these boards or get told to do by a tech. If you notice about every 4th or 5th page has someone posting about this problem. The above suggestion is the most recent thing I tried (from reading posts here in this forum, not from an Apple Tech) and it has come out of sleep for the past 30+ tries without a problem. This is not to say this is IT(the final sovle), because it has been known to go on a good run for a week or so and then come up again. This 'fix' however, has been the most promising. If it continues to work, I will let Apple know and hopefully they can fix the bug. They have all sorts of case history with me on this problem.

What is the technical 'cause' of the infamous iMac black screen problem?

Can anybody shed some light on what technical malfunction exactly causes the infamous iMac black screen problem? The common solution seems to be a logic board replacement. But what exactly is broken on the logic board? Is it the Geforce chip? Some kind of external driver circuitry? Or something completely different?

I was referring to the many problems also described in this thread (and also in many other places):
http://discussions.apple.com/thread.jspa?threadID=196774&tstart=0
In specific I am referring to machines where all of this applies:
- internal monitor stays black after power-on
- computer boots normally
- external display works normally
- internal display backlight works and can be adjusted in brightness, but all pixels are black
- PRAM reset doesn't help
- NVRAM reset doesn't help
- PMU reset doesn't help
- reinstalling OS / booting from CD doesn't help
- machines with this problem sent to repair come back with a replaced logic board
I'm looking for more information on the technical cause of the exact problem as stated above. So I can attempt to repair my iMac

Intel iMac Black screen on wake up from sleep

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