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Is my logic board, or my power supply, or my RAM gone?

Hey guys,

My imac won't start up.

When I press the power button I can hear the hard drive and the fans working but no chime.

I've checked the RAM, by replacing.

When I took off the LCD to determine if the failure is related to a faulty LCD, I powered up the machine without the LCD connected. This resulted in blowing the fuse.

The diagnostic LEDs 1-3 are lit.

Has anybody a clue on that?

Mit freundlichen Grüßen


Update (12/03/2015)

I replaced the ram by a certified one. That should be fine.

But still the same behavior.

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Remove the RAM and press the power button. Do you get beep error code?


It sounds like it's getting power if you can hear the hard drive and fans power up.


If you could try starting it without the RAM we can see what part of the POST it is failing. If you don't get a RAM error code we know it isn't even getting to that point. Which means the issue you're having is before the RAM check, which would lead me to believe that it is a processor or Power Supply issue since those are both checked before the RAM. If it's after then it could be an overdraw from the HDD or ODD


Can you discern the desktop with a flashlight?


since you heard the fan, it means its getting power, therefore the problem lies with either the display of the hard drive, check on those things and let me know how it goes so i can know how to help you


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If you get no picture (black screen) the 3rd system LED is lit.

No sound (chime).

Fans kick on and second system LED is lit.

Then it is most likely your main board that has gone bad.

If it was the LCD, you would still get your chime.

If it was the HD you would still get a picture, usually to black and white pring of apple logo or a flashing folder with question mark.

Bad RAM you still would get a picture.

Bad power supply no LED's, fans or HD powering up.

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On this model the inverter fails a lot.


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AndreGER sera éternellement reconnaissant.
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