Will not power on

Hi,

My iMac is connected to an UPS and I had shut it down last friday before leaving on a business trip. Once back home, I tried to power it on and it simply wont :(

When I hook the power cord to the socket(both UPS and direct), I hear a buzzing sound from inside the iMac.

Once I press the power button, I hear the startup sound and then it powers off. Subsequent power button presses does nothing and also I dont hear the buzzing sound until I physically remove the plug from the socket and reconnect it.

I removed my 3-party purchased RAM and is still the same.

Please help solve the problem :(.

Answered! View the answer I have this problem too

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I was wondering if you ever had any luck with diagnosing this issue. I am having exact symptoms with LED observation. The only difference I see is that this all happens for me without pushing the power button (all sequenced after the external power cord is plugged in). It seems that the problem is with the power supply but I want to make sure before ordering.

For background of my situation: The computer was plugged up (surge protector) and running during a power outage. Never turned back on. Took it to the Genius bar and we decided my issue was a bad cord (The iMac booted with his power cable). After using a know working power cable at home the computer went back to no dice. Brief fan and dead. I disassembled and noted the LED sequence as you have described.

Was you're computer involved in a power outage as well?

Thanks for the help in advance!

-Jeremy

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Mayer, Thanks for your comments. Observations : a) When the power cord is plugged, the first LED (From the bottom) turns green and stays green. b) When the Mac power on button is pressed, the second LED turns green and the third LED turns green for a brief second (with th fan also spinning for a second) and then all of them turn OFF. The first LED remains OFF until the power cord is unplugged and plugged back in the socket again Please guide with the next steps

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Chosen Solution

Remove the Frame. Plug in and check what you're getting on the LEDs.

Diagnostic LEDs are to the right of the RAM slots (this may be covered by a piece of black electrical tape extending up from the bottom edge of the logic board). Ple4ase let us know your results before buying anything as #1 should be on even if the power supply is bad. See if you can discern where the noise is coming from.

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

LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found.

If third LED is not visible after power on:

• Verify that MXM video card is seated properly

• Verify logic board

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Mayer, Thanks for your comments.

Observations :

a) When the power cord is plugged, the first LED (From the bottom) turns green and stays green.

b) When the Mac power on button is pressed, the second LED turns green and the third LED turns green for a brief second (with th fan also spinning for a second) and then all of them turn OFF. The first LED remains OFF until the power cord is unplugged and plugged back in the socket again

Please guide with the next steps

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What can I do, if I know, that the logicboard or the videocard is the problem?

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Replace them

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Badrinath B will be eternally grateful.
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