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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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No chime, no screen, LED #1 ON, Fan running full speed

Hi guys,

I’m struggling very hard to get this Mac to work again. The screen got broken and since then the Mac sat around for a few months before I had the chance to get it.

I opened it up to check the inside of it which looks totally fine (just a bit of dust).

As the screen is broken LED 1, 2 and 3 should light up normally.

Instead only LED 1 is lit up and the others are off.

The Mac basically turns on as the CPU Fan is spinning at full speed.

I’ve checked all cables (disassembled it like 6 times already), applied new thermal paste in the process and rebuild it all again.

Sadly I don’t have a spare PSU or Logic board. Can anyone help me?

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If the fan is racing it’s safe to say the power supply is working as the SMC logic is doing what it should be trying to keep the system cool as the thermal sensors in the display have been disconnected so the system goes into Safe Mode.

Did you get a new display yet? Your system will need it to work properly.

So looking at the onboard diagnostic LED’s which you are still having problems

LED 2 - Indicates that computer is turned on. This LED will be ON as long as computer is turned on (but is not asleep) and power supply and voltage regulators are working correctly. I think given the fact SMC is working (fan racing) the onboard VRM’s have an issue powering the CPU. As you replaced the thermal paste I’m suspecting the CPU chip is not properly seated or the one or more of the socket pins are bent. Did you replace the chip with another? Then its the wrong CPU.

LED 3 - Indicates that computer and graphic process unit (GPU) are communicating. This LED will be ON when computer is communicating properly with the GPU. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the backup battery (on back of logic board) may need to be reseated, or the logic board may require replacement. This won’t happen until LED #2 has passed

LED 4 - Indicates that computer and LCD panel are communicating. This LED will be ON when computer is turned on and video signal is being generated. If LED 4 is ON and there is no image on display, then the LCD panel or the cables between LCD and logic board might be installed incorrectly, or need replacement. This won’t happen until LED 2 & 3 have passed and you have reconnected the LCD to your system via the extension cables or directly.

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Thanks for the reply Dan! I’ve double checked the pins and it’s all positioned correctly before I’ve sealed it up together again. Right now I don’t have a new Display. The old display is broken (someone hit it) but nonetheless the sensors of the display should keep working, right? I could try to get a different i5 and check it with that if that’s what you’d do.Besides the iMac should be able to power a external monitor even without the main display working or am I wrong? I’m working as a IT Technician for years now but this is my first iMac repair. Thanks for the tips and help!

由完成的

Did you use the proper procedure to tighten the CPU heat sink screws? Follow the same logic you use on a swapping out your tire for a spare! have you tighten the screws across in a criss-cross fashion? If not then the chip could have been damaged (cracked) from stress.

If you are already try a new chip and need to buy one just get the 3.5 GHz i7 (I7-3770)

由完成的

@danj

Yes, I did tighten the screws in a criss-cross fashion. I followed the iFixit tutorial step by step and the iMac still won't turn on. I also tried to use a external Monitor with a mini DVI to DVI and mini DP to DP cable - no success sadly.

I could try and get a used i5 4770 or i7 4770 somewhere in our warehouse. Maybe I'm lucky.

DO you have any other idea than a complete swap of the logic board?

Will come back as soon as I have some results.

由完成的

@reikyabiku - You'll need either:

● 3.4 GHz Core i5 (I5-4670)

● 3.5 GHz Core i7 (I7-4771)

The logic board won't accept anything else iMac14,2.

由完成的

Ok so I've swapped the CPU - all pins on the logic board look great, the old CPU looks totally fine as well. Swapped it with a i5-4670. I've also swapped the battery that's on the motherboard just to make sure it's not the battery as well.

Now nothing is happening if I try to power it up. 1st LED is still on.

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