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Steve Over Level 1 Level 1

iMac (21.5-inch Mid 2010)


When I boot normally it sticks on a grey screen with the Apple logo.


Safe boot works fine,  but when I hold down "D"  it just sticks on the grey screen again, as if "D" does nothing. 

iMac, OS X Mavericks (10.9.1)
Reply by Steve Over on Feb 8, 2014 3:07 AM Helpful

It was a separate video card,  I removed it with the help of these instructions 980

I did a reflow and reassembled, AND IT NOW WORKS 100%


It wasn't quite as easy as it sounds, I am a PC engineer but I have very little experience in diagnosing iMac problems.


Thanks again for all of your help, I couldn't have fixed it without you!

All replies

  • rkaufmann87 Level 9 Level 9

    What version of OS X was installed on the computer when it was shipped, AHT may be on the original install discs. Please carefully read Apple's instrucitons in Apple Hardware Test

  • Steve Over Level 1 Level 1

    It's iMac (21.5-inch Mid 2010)   It has Mavericks, that I've just re-installed via the Internet Recovery.

  • Steve Over Level 1 Level 1

    I think it might be a faulty GPU

  • rkaufmann87 Level 9 Level 9

    Did you receive an error code when you used AHT? If so that confirms there is a hardware problem, however to be honest AHT is not totally reliable which is why you need to run in multiple times in extended mode to see if it picks up any errors. It sometimes can miss problems but if it detects them then they are usually accurate. However if you want to know for sure then simply take it into an Apple Store or AASP and have it professionally diagnosed. Trying to do it yourself without proper tools is guesswork at best and in the long term can be much more expensive.

  • Steve Over Level 1 Level 1

    Thanks for the reply, but as you can see from the name of my post, I can't get AHT working "No AHT when I hold down D"


    There isn't an Apple Store near me, so it's down to me to fix;   I have repaired GPU faults on many PC laptop and even a few MacBooks.  But before I tear this machine to pieces I would like to run Apple's diagnostics.

  • rkaufmann87 Level 9 Level 9

    Re-read the instructions for using AHT, I can assure you it's there you are just making a goof. As for an Apple Store, OK, however I'm sure there is an AASP in your area. To help you find one please click AASP Locator

  • WZZZ Level 6 Level 6
    Mac OS X

    It may be you've lost D key booting to the AHT if you ever reformatted the drive, or done a reinstall. That happened to me. What you can do to restore it is to open the original Applications install disc that came with the Mac, with normally hidden folders and files unhidden. (Instructions for that below.) The AHT is the normally invisible folder  .diagnostics  in /System/Library/CoreServices/


    Find it on the install disc with all files/folders unhidden--you won't see it otherwise--and just manually move it over to that location and you should be able to boot to the D key again. (But, important,  before doing that, check to see that it is in fact missing.) After moving it over you must repair permissions using Disk Utility because the correct permissions will be wrong from having used the Finder to move it. If you don't see it being corrected when you do a permissions repair, post back and I will give you instructions for doing that directly.


    To toggle visibility on:


    Open Terminal in Utilities and copy/paste:


    defaults write AppleShowAllFiles -bool true


    To revert to the normal, hidden state


    defaults write AppleShowAllFiles -bool false


    After entering either of these commands you must force quit the Finder


    killall Finder

  • Steve Over Level 1 Level 1

    Thanks.  Yes I did format and re-install, but I don't have the original Install disc and I'm not even sure what version it came with.    It's a Mid 2010, would that be snow leopard?


    I will check out your instructions later, to see if AHT is already installed.

  • andyBall_uk Level 7 Level 7

    If you reinstalled (or just upgraded from the original OS), it won't be there.



    has a link to a dropbox file which appears to include the right one for your model. Many are available to download directly from Apple, but not that one, so far as I've seen.

  • WZZZ Level 6 Level 6
    Mac OS X

    You can get the original discs for your Mac by calling Apple and giving the serial #. There is a relatively small charge for this.

  • Steve Over Level 1 Level 1

    Thank you all for the replies.


    I've managed to get into AHT by installing it from the file andyBall_uk suggested,  but it just sticks on "Probing your hardware, this might take a minute";   Is that a bad sign or is it the wrong AHT that I've installed?

  • babowa Level 7 Level 7

    Yours would have come with 10.6.3 - 10.6.6; see the instructions for computers shipping with 10.6.7 or earlier here:



    Unless the others' instructions work, it appears you will need your install disks.

  • andyBall_uk Level 7 Level 7

    It might be wrong : what does this show in Terminal for the board-id (F-number) ?


    ioreg -l | grep board-id

  • Steve Over Level 1 Level 1

    F2238AC8   is that Lion?

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