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James, Sr. Mac Support Expert
Category: Mac
Satisfied Customers: 15908
Experience:  Mac Expert
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iMac will not boot. Startup sound occurs, then loops reoccurring

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iMac will not boot. Startup sound occurs, then loops reoccurring with out showing white startup screen. When a screen appears it is a red and white checkerboard like a plaid on one side, white on other. Nothing else occurs. Have tried complete power down without resolution. Allowed computer to completely cool for 24 hours without resolution. Same outcome. Believe hard drive complete failure or bios failure?

At any point, do you see the Apple logo?


Customer: replied 3 years ago.
Thank you. It does sound like a BIOS/board malfuntion, but please try this for me:

  1. Shut down your Mac.
  2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
  3. Turn on the computer.
  4. Press and hold the Command-Option-P-R keys before the gray screen appears.
  5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
  6. Release the keys.

Anything happen?

Customer: replied 3 years ago.
No startup sound replays and plaid screen appears
Thank you - I understand.

I'm afraid this confirms the problem is with the computer's BIOS or board - they need to be replaced. There is a very good chance that the data on the hard drive is instact, and that once repair is complete, you will be able to retrieve all your files, pictures, etc - without any loss.

I know this is not what you want to hear and am very sorry to give you this piece of bad bad news, but it would be unprofessional of me to do otherwise. I hope you understand and that you are not going to shoot the messenger...

If you have any other questions or need more information, please ask me – I’ll be happy to respond!
I'd appreciate it if you can rate my service using the faces below my answer.

Many thanks,

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