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Model A1225 / Early 2009 / 2.66, 2.93, or 3.06 GHz Core 2 Duo processor

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iMac 24" not powering up

Hi.

I have a 2009 24” iMac that will not power up any more. I have looked at the 4 LED’s and with the mains cable attached, the first LED is lit, but as soon as I press the power button, the LED goes out.

I replaced the power supply with a new A1225 unit from Ebay, but that didn’t fix it, the first LED only came on and back off as the power line as attached.

Any ideas would be really helpful.

Update (04/24/2021)

Here’s the damaged board.

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Sorry. It was shut down and there was a sizzling noise followed by a pop and then I smelt electrical burning so I in plugged it. I didn’t have a look inside for about 3 months and I can’t smell anything inside.

Sometimes when I try to power it up, a couple more of the led’s flash before they all go out.

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@imachelp - That offers a good clue. We have a burn't component on the logic board. Time to take it fully out and carefully inspect each component look for discoloration on the part as well as staining on the logic board.

Reference these photo's to compare against yours:

Front Side

Back Side

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Hi Dan. Thank you for that. I'll go and take it apart again and have a good look.

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Think I might have found the problem. How do i attach photos to show you.

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Hi Dan. I have given up trying to upload the photos, but with your assistance, I have pinned down the fault which turned out to be a blown capacitor on the graphics card. I removed the card and the Mac fired up, so just need to fix the graphics card. Many thanks for all your help.

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@imachelp - Review this breakdown on the onboard diagnostics. Your issue is likely something on the logic board that has an issue. Can you give us a bit more on what happened.

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. 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.

Note: this LED is not used on systems with the integrated graphics.

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.

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Hi Dan.

The number one LED is lite when the power lead is connected but as soon as I press the power button, it goes out and stays out until I disconnect and re connect the power lead. The new power supply only lite the first LED briefly as the power lead is connected but after that, nothing.

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@imachelp - Yes, I got that from your original question. What lead up to this is the question. Can you give us more details on what transpired from a working system to this dead system.

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