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Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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iMac 27” EMC 2639 won’t turn on

So I’ve got an iMac that won’t boot up.

When turned on there’s a faint sound from inside but nothing like a normal boot up. If the power button is held down and the power cord is plugged in the fan turns on very loudly.

I purchased the tool to open it up and have inspected the LED diagnostic lights. The only light that comes on is LED #1.

This is true when turning it on with the screen plugged in and also with it removed. Any suggestions with what my next step should be?

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Remove the RAM and try one module did that improve things?

If not your logic board is gone.

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I agree with Dan. LED 1 means the power supply is working. If you can disconnect all the peripherals like the hard drive and memory, see if #2 goes on. Or if you get the "bong" sound.

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I totally disagree with @edwoodjr rokin154. All the #1 green means is the power supply is getting trickle power (Not that it is working at all.)

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Thanks for the input guys. Here’s where I’m at now. I tried turning it on with the ram removed - still just led 1 on. Also tried turning it on with the hard drive disconnected - same thing, just led 1 on. I disconnected the power supply and turned it on and was quite surprised that led 1 was lit. This makes me think that it quite possibly could be a bad power supply. Thoughts???

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My thoughts on the bad power supply might be incorrect. Previously when I plugged it in and held the power button down the fan would come on very loudly. I repeated this action with the power supply disconnected and the fan did not come on. Maybe the power supply is ok.

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Replace the power supply:

iMac Intel 27" EMC 2639 Power Supply Replacement

The LED's are on the logic board to the right of the RAM slots and between the RAM slot and the HDD sata connector

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.

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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@mayer - He has the Diagnostic LED #1 lit. So the power supply is suppling power to the logic board.

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@danj no it's not. Now if the #2 LED was on I would agree.

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. Most bad iMac power supplies will light up #1.

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@mayer - Your right my mistake!

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I have ordered a new power supply and will post an update once it’s in.

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Okay, so I put in a new power supply and I’m still at square one. Only led 1 comes on. I’m at a loss for where to proceed next.

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Hi Roger B., I have the exact same problem with my imac 27 emc 2429. Only the first LED comes on when I plug it into the wall. When I pressed the power button, the fans came on for 2sec and turned off. I ordered a used psu on ebay and the same problem remained. I’m about to order a logic board. Could you test your psu and see if you get the same voltage at each pin as I show in the attached picture? If you get the same voltages with your working psu, then I would need to buy a new logicboard. Thanks!

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