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Model A1419 / EMC 3070 / Mid 2017 / 3.4, 3.5 or 3.8 GHz Core i5 or 4.2 GHz Core i7 Kaby Lake Processor (ID iMac18,3) / Retina 5K display. Refer to the older iMac Intel 27" Retina 5K Display (Late 2014 & 2015) guides as the system is very similar.

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GPU faulty after CPU replacement, mac boots

I replaced the CPU in my 2017 5k iMac with an i7. Everything went fine but now the iMac does not generate any video output. Neither on the internal display nor on an external one. I tried putting the original CPU back into it, same results. I narrowed it down to the GPU because it chimes and boots normally, I can log into my account using the keyboard and activate VoiceOver (which reads the display’s contents out for me), so it definitely still works. However, only 3 (of 5) diagnostic LEDs light up.

The LVDS/DP connector and cable both look fine visually. The display should also be fine. An external monitor does nothing, it doesn’t wake up, no signal, no backlight nothing. So definitely no kind of video output whatsoever. Same for the internal display.

Now my question: I have thorough microsoldering experience and an electronics lab, but have never repaired an Apple iMac before. I neither have a schematic nor a boardview for this iMac model. The ones I found on the internet are too different to find the test points on the board. Is there any other way I can troubleshoot this GPU problem? I’d really like to repair this logic board. Anyone know some points where I could measure some voltages? Thanks in advance!

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Frankly, I think your issue is still within the CPU logic. Replacing the CPU chip in this series is a bear! Apple placed the socket in the worst placement for anyone to replace the chip. Between the RAM cage and the serious tension springs.

I’m suspecting you bent some of the socket pins so they are not making contact to the chip. So the video lines are not connected. The other possibility is you over did the paste getting in onto the small SMD devices which sit on the top part of the chip either the CPU or GPU.

So its time to go back in and inspect things and how about posting some pictures so we can see as well Adding images to an existing question

Your other option is to just bite the bullet and replace the logic board, of spend sometime over on Louis Rossmann YouTube as he spends must more effort on logic board repair.

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Marlon Arend sonsuza kadar minnettar olacak.
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