Power button does not start computer. Guessing Power supply or cord?

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iMac Intel 27" EMC 2309 & 2374

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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xxdaz316xx @xxdaz316xx

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Gepost: 5 mei 2020

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Power button does not start computer. Guessing Power supply or cord?

Recently my 2009 iMac 27” turned off and the power button does absolutely nothing when I push it. No fans. I push it and no response.

First I thought I needed to buy a new power cord to plug into the back of my iMac but someone suggested that the power supply may be bad.

So then I took apart the computer and got to the power supply and was wondering if you can take a look at the circuit board to see if this might be the culprit? I noticed a lot of yellow stuff in one section as you can see in the pics.

*UPDATE 1*

green LED on diagnostic board after I plug in the AC cord

*UPDATE 2*

*Removed Logic Board / GPU*

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Dan @danj Rep: 478,9k Self employed contract worker 35 329 970 · Answer 1 · 2020-05-05T14:57:03-07:00

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Dan @danj

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Gepost: 5 mei 2020

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Re-assemble your system, then plug in your power cord. Locate the onboard diagnostic LED’s coverd by black tape in the bottom left of your logic board

Here's a breakdown of the onboard diagnostic LED's:

LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. 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 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. 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 display 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 LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement.

Let us know what you discover!

Here’s a picture of the logic board power button connection

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Ja Nee

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Hey Dan,

Thanks for that. It was so hard trying to remove that tape covering the diagnostics LEDs, but after using tweezers I finally did it to troubleshoot this whole ordeal.

I plugged in the AC cord and noticed 1 green light up turned on,

so does that mean that’s a good sign the logic board is in good working shape and detects the power supply and that my power supply work and the AC cord still works? But my problem is that the computer still doesn’t turn on. When i press the power button, nothing happens. No fans. No sound. It’s like the button isn’t being pushed at all. Any idea on what I should check next?

9 mei 2020 door xxdaz316xx

Sorry - LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.

So you'll need to replace the power supply first.

9 mei 2020 door Dan

When I unplugged the power supply the light is not showing up on the LED anymore. Is this normal? So if the power supply was working and I plug the AC cord in, then if everything was working, I should have 2 green lights on correct?

Check out the pictures that I updated on my main post to see the green light on

9 mei 2020 door xxdaz316xx

The LED #1 is just telling us the trickle voltage is present. iMac's use vampire voltage to hold its settings, thats what the LED is telling you the vampire is present, and give us the clue the AC cord is connected nothing more!

We need to see LED #2 to know the power is getting to the logic board. Did you break the LED? I only see three?

9 mei 2020 door Dan

I understand. So since only LED #1 turns on when the AC cord is connected and not LED #2, would you recommend that I purchase a new Power Supply because if the Power Supply was working, then I should be seeing 2 LED on when the AC cord is plugged in, correct?

9 mei 2020 door xxdaz316xx

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