Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor

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iMac doesn't turn on. No fan movement. Only LED 1 on Motherboard.

My Mid 2011 27" iMac EMC 2429 will not boot. The display doesn't come on, out of the 4 LED's on the Logic Board, only the 1st LED lights up, the other three are not.

My question is, I know it's not the PSU because the Logic board recognizes that it's getting power. Could it potentially be a failed Logic Board? and what does it cost to get it replaced?

Upon further inspection:

Removal of LCD screen. When powering on, there is some noise of noise activity from the PSU. No other activity seen or heard from other components. Upon holding the power button for 5 seconds, sequencing a hard shut down of the system; the noise level of the PSU drops from a 5 to a subtle 2. Upon further inspection of the PSU, there is an white-ish discoloration around the border of the unit. The middle of the unit, excluding the border has a glossy, almost oily presentation.

Replaced the power supply unit per advice. Nothing has changed.

Upon testing voltage of Pin 11, we have a 12.01V reading on the voltmeter.

No voltage reading from Pin 4.

Coin battery voltage measures at 3.0V.

Looking for some advice about where to go from here. As stated before, I replaced the power supply unit with a brand new PSU from iFixit and nothing changed.

Answered! View the answer I have this problem too

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See if Apple will replace the video card, do not mention that you changed the power supply. I know the LEDs do not show this but experience says this is the problem: https://support.apple.com/en-us/HT203787

Due to high demand Apple has extended this period of time in a lot of cases, mention the term, "Warranty Exception".

The last four characters of the serial number must contain one of the following groups (for example, xxxxxxxxDHJQ):

DHJQ, DHJW, DL8Q, DNGH, DNJ9, or DMW8

DPM1, DPM2, DPNV, DNY0, DRVP, DY6F, F610

If the iMac falls within one of the above the serial number categories and is confirmed to have the graphics card issues, Apple will replace the AMD card free of charge up to three years from the computer’s purchase date. Additionally, if an affected iMac user had their graphics card already replaced at cost, the customer is said to be eligible for a refund.

http://9to5mac.com/2013/08/16/apple-open...

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Any update here before I buy this power supply?

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Benjamin Luman will be eternally grateful.
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