iMac Intel 27" EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz) ID iMac10,1, EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz) ID iMac11,1

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iMac wont start, only diagnostic led 1 on

My imac wont give any sign of life.

Only the first diagnostic led is on when connected to power. Nothing happens when i press the button.

Does this mean my logic board is broken? Cause replacing that is way to expensive.. :(

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2 Answers

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Casper Smit, that sounds like it would be a very drastic replacement. The very first thing I would do, is to check this out:"

LED #1

• Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will remain ON whenever the iMac is connected to a working AC power source. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power source is disconnected or the power supply is faulty.

LED #2

• Indicates that the main logic board has detected proper power from the power supply when the computer is turned on and that logic board voltage regulators are functioning properly. This LED will be ON when the computer is turned on and the power supply is working correctly.

LED #3

• Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.

LED #4

• Indicates that the computer and the LCD panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the display, then the LCD panel, the LED backlight board, or the cables between might be installed incorrectly or need replacement.

LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

• Verify AC source

• Verify known-good AC cable is connected

• Verify cable connection between AC inlet and power supply

• Verify cable connection between power supply and logic board

• Verify power supply

'''LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

• Verify power button connection to logic board

• Verify power button functionality

• Verify cable connection between power supply and logic board

• Verify power supply

• Verify logic board

And as you see, the logic board is on the bottom of the list of items to replace. I would start by checking all connectors and cables, and if you need to replace anything start with the power supply. Do check the capacitors on the PSU, make sure that they are not bulging or leaking. That would be an easy fix.

My usual disclaimer of course is that I am not a Mac person and I am sure that the Mac gurus can help you more than I can. Good luck!

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Thnx for the reply!

Any idea on how to verify power button functionality?

Its my last hope i guess..

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I know its an old post but I have this problem too. I found out with removing the videocard the second led is turning on as well and the computer starts. As soon as I put back the videocard it won't do anything. Only first led is on. I saw a lot of problems with videocards in iMacs but never that the card prevented the system from starting. Its an 27 inch 2011 model.

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I fixed it by replacing the graphics card. Got one from ebay. Goodluck!

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Casper Smit will be eternally grateful.
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