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Modello A1419 / EMC 3070 / Metà 2017 / processori Core i5 3.4, 3.5 o 3.8 GHz o Core i7 Kaby Lake 4.2 GHz (id ImAC18,3) / Retina 5k display. Fai riferimento alle guide del modello più vecchio dell'iMac 27" Retina 5K display (fine 2014 & 2015), dato che il sistema è molto simile.

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iMac doesn't boot anymore, Service LED one and two light up

Hey there folks, I have an IMac 27' 2017 A1419 EMC 3070 with 32 Gig Ram and the I7 7700k.

It startet with random shutdowns, after unplugging it for a while it was fine for a few minutes and then the same procedure all over again., until it wouldn't boot anymore at all, just starting with the fan on 100% and then shutting down, repetedly doing that.

My suggestion was Overheating so I took it apart and cleaned everything + new thermal compound on GPU + CPU.

Now the IMac only shows the first two service LED's in green and the fan starts normally.

Any Ideas on why I can't get an Image or something?

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for those who have the same problem... I repasted the CPU and the GPU to make sure it isn't overheating, while the Board is out I'd also change the SMC-Battery (CR2032). After assembling everything back together, try one Ram instead of four and Reset both the SMC and the NVRAM. After that you should hear the booting sound of the mac and you should see the apple logo, make sure to check for all 5 service LED's to light up green and be sure that both display cables are connected to the board and the display.

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I’m suspecting the CPU is not properly seated which is a common issue in the Intel iMacs! Time to open the system back up. Also make sure the TIM hasn’t migrated to the socket as well as that can mess things up as well and inspect the socket contacts for damaged pins as well.

Given the age you might need to replace the NVRAM battery. Of course it’s located on the back side just under the heatsink pipes! But as you are all ready heading in I would replace it. Take a voltage reading of the battery and the replacement to double check both.

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It actually worked, I reseated everything and replaced the NVRAM Battery. Now it works and also makes a sound when I type or when I press the option+command+P+R buttons for the reset, but I don't have an display output even though all 5 LED's are on and green. Do you possibly have another tip for that? I sadly don't have a monitor for USB-C Connections

da

@sveppg - this series offers mDP or Thunderbolt Display support it doesn’t offer USB-C connection. If you have a HDMI display you can get an adapter to convert the signal.

da

It actually supported the USB-C connection for external display's. But anyway everything works after replacing the internal battery and reseting the nvRAM and the SMC.

da

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Sveppg sarà eternamente grato.
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