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Thread: iMac fails to boot, any advice welcome

  1. #1
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    Exclamation iMac fails to boot, any advice welcome

    Hi there,

    I was given an iMac for my birthday by a friend of mine as he has built his own PC and no longer needed his iMac. It's a mid 2010 model, 21.5" with the RAM upgraded to 12GB (two 2GB and two 4GB modules) running Mavericks.

    It worked perfectly since I got it in February, but has now become completely unusable.

    Basically it entered a continuous reboot cycle on Tuesday and I have been unable to solve the problem. After attempting multiple times to repair the hard drive (through recovery mode and single user mode) I decided to attempt booting from a USB external hard drive. The external has a fully functional version of Mavericks on it (installed from a friend's MacBook Pro) but won't seem to boot from it.

    Each time I try to boot it comes up with the progress bar under the apple logo (which I have been led to believe is some kind of registry check performed when entering safe mode). The progress bar completes and the mac then shuts off instantly.

    In single user mode I have run fsck which returns an "incorrect number of thread records" error and won't repair. I have attempted repairing through fsck_hfs and this also does not work.

    I found somewhere online that there could be an issue with my RAM, so I have checked the RAM as best I can since I can't get the iMac to perform any form of hardware check. One of the RAM modules was incredibly difficult to get out and difficult to put back in, so I have left it out of the iMac. The problem is persisting.

    Yesterday I managed to get it to boot into OS X, but after a few minutes, it shut off completely once again. Now it is once again starting up, the progress bar appears and when the bar completes, the iMac shuts off instantly again.

    I would rather not have to take it into the Apple Store as I am a student and I expect they will charge me more money than I have to repair it.

    If anyone has any advice for me, or if any additional information is needed, I will reply as soon as possible.

    Thank you.

    Chris.

  2. #2
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    Default Hang in there my friend

    We've got some good people on the forum. I'm going to let someone else handle this first... I'm not so technical inclined with the newer models. I've got a 21.5" myself.

    I have an idea or two but lets see what others say first. Save me from guessing but I'll search and read some and if I find a fix I'll post it.

    I'm thinking an OF reset but lets wait.

    Welcome to MacGuru's

  3. #3
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    From how it is behaving, sounds like a failing hard drive. That progress bar you see is the system running the same file system check as you were command line. Can fix some things, but not bad sectors or other hardware issues.

    It should boot from the external, depending on how that OS was installed. Did you install from this machine, or was it installed from a different model? It is possible that it would not be bootable from your Mac....

    To test/repair yourself, you will need to boot to an external drive. Any chance you can reinstall 10.9 on the external? Or round up another external to use?
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  4. #4
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    RAM would likely not cause the issues you see, but you can pull a pair out and test, then swap the other pair and test.

    Doubt this will help you, but one thing to rule out.

    When you say the machine shuts off....does it power off, or freeze/lock up?
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  5. #5
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    If it turns out to be a bad HD, here is the process to replace it. Not to bad for those handy and comfortable with computer repair.......but a bit intimidating for first timers.

    You don't have to take it to Apple, but you should find a shop/tech that is familiar with iMacs. About an hour of labor plus about $80 for a new hard drive, depending on the model/size you want.

    So something around $150-200 for a good tech.....if the HD is the issue.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  6. #6
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    Default Additional information

    I installed OS X Mavericks onto the hard drive using my friend's MacBook Pro, but it won't boot. I'm not sure if this is because the iMac simply won't read the drive and is trying to boot from the internal hard drive, or if it's because the external is also damaged.

    When I say it shuts off, I mean that the screen goes black and the power is instantly off, it does not perform a shut down cycle.

    Is there any way of knowing for certain if the internal hard drive is the only issue or if there are other hardware issues without trying to run diagnostic tools (since these don't seem to work either)? Is there anyway or running diagnostic tools from single user mode?

    Thanks again.

  7. #7
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    When you attach another hard drive to boot from, you need to tell the computer to boot to it. Hold the Option key down during boot and it should give you a screen where you can choose which drive to boot to.

    Rick
    molṑn labe'
    "I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin

  8. #8
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    Would the iMac be not wanting to boot because the OS was installed my a MBP -- are they machine specific enough to make that difference?

  9. #9
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    Might have some weird stuff, like a battery status indicator in the menu bar, but it should boot the iMac.

    Rick
    molṑn labe'
    "I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin

  10. #10
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    Quote Originally Posted by ricks View Post
    Might have some weird stuff, like a battery status indicator in the menu bar, but it should boot the iMac.

    Rick
    As long as the MBP is the same vintage or newer. If it is a previous generation model (2009 or back)……it may not. There are many exceptions, but the basic rule has been:

    Newer OS installs (installed on a newer Mac) will always boot older Macs, but older OS installs (installed on an older Mac), might not boot on a newer Mac.

    Usually it has to do with drivers for GPU/CPU/chipset that did not exist, and are not installed on the older machine, but are required for newer hardware. Not as clear now that we are in a post-DVD OS installer world, but there were times when a newer hardware set would only boot from the OS disk that shipped with the machine; not with a retail version until the next retail version shipped…. Messy, and not that common, but possible.

    First things first, hold the Option key and see what you get.

    As for the shutdown…….not a common symptom of a failing HD. Could be a power supply or something else. But again, the first thing to do is get it booting from a different (external) HD, and test.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

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