Is my 5k LCD Dead?

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iMac Intel 27" Retina 5K Display (Mid 2017)

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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Electric Wheels @ewheel

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发帖于: 2023年1月20日

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Is my 5k LCD Dead?

Hi all and I am stuck as to what is causing my iMac to not work properly?

It all started last week when I booted my iMac 27" 2017 5k which is hooked up to a LG UltraFine 27" external monitor and only the LG showed the desktop whilst the iMac was just blank (no backlight and no image), so I rebooted and then nothing came on and the iMac was in a constant boot loop chime. Tried keyboard commands but all where unresponsive whilst the machine was in boot chime loop.

I next tried ram pulls but that made no difference and produced no beeps etc. I then took my iMac to a local IT repair shop that deals with Apple products and a week later they called me to say the PSU board is ok, SSD and HDD where all good and the machine was running to an external monitor but without the main LCD screen on iMac, if the screen was re-connected it went back to the boot chime loop with nothing on either screen?

The IT shop said they had no other 2017 models to test parts with and that it was either my LCD the has failed and if that did not fix the issue then it is a bad logic board? I would like to know if possible what part is more likely to be causing the issue as I cannot afford to buy a logic board and LCD as that will cost me more than I paid for the machine setup 2nd hand for £900

@danj I fitted the new screen on today and nothing but the boot chime loop. Disconnect the screen and iMac boots to external monitor but fans are running at max revs.

I took pictures of the sockets and cables as best I can, the back of the original screen looks to have some heat buildup at some point

@danj this is the iMac diagnostics which is saying SMC and Graphics?

I have a logic board arriving tomorrow to test that part as the new screen is being sent back.

@oldturkey03 thats the display cable end and damage whatsoever along the cable. As before the machine has never been opened until now so the cables have never been touched or moved

@oldturkey03

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@ewheel if you still have it disassembled, post some good pictures of your display connectors both ends, both sides and the area around the board connector 在已经存在的问题里加入图片

由 oldturkey03 完成的 2023年1月21日

@oldturkey03 I have posted pictures above

由 Electric Wheels 完成的 2023年1月24日

@ewheel - The SMC and the Display (not graphics) is expected as you didn’t have the display plugged in (right?)

You did use the cable that came with the replacement display?

I don’t see any issues with the connectors. This is an odd one for sure!

So we can surmise this is a loading issue when the display is connected then, when connected the load is to much.

由 Dan 完成的 2023年1月24日

@danj The main display was not connected and only the external 27" LG Ultra Fine 5k monitor was connected. I could only use my current cables as the new screen came bare bones so had to move the sensor and display cable over to the new screen, I checked all the sockets etc and nothing of concern. I have ordered a display cable too if it turns out to not be the logic board. The system loads up fine on the external monitor with the fans on max so cannot see why it would not boot just the iMac screen being a 5k screen just like the external? My main concern when I first looked at the back of the origional iMac screen was the heat marks next to the display cable and another down by where the fan would be located?

由 Electric Wheels 完成的 2023年1月24日

@ewheel thanks for doing that. Can you do a straight down view of the board connectors and surrounding components? also, can you clear up the last two images and zoom in on the actual connector please? I am just following a hunch

由 oldturkey03 完成的 2023年1月24日

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Electric Wheels @ewheel

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发帖于: 2023年1月25日

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Update @danj @oldturkey03 I have my iMac up and running and it turned out to be the logic board that was on it's way out even though it worked on external monitor. I have added 13 or so pictures of the old faulty logic board too. Thank you so much for helping me out with this puzzle and at least I now know how to take apart and rebuild a complete 2017 iMac

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@ewheel if you still have it disassembled, post some good pictures of your display connectors both ends, both sides and the area around the board connector 在已经存在的问题里加入图片 — oldturkey03
@ewheel - The SMC and the Display (not graphics) is expected as you didn’t have the display plugged in (right?)

You did use the cable that came with the replacement display?

I don’t see any issues with the connectors. This is an odd one for sure!

So we can surmise this is a loading issue when the display is connected then, when connected the load is to much. — Dan
@danj The main display was not connected and only the external 27" LG Ultra Fine 5k monitor was connected. I could only use my current cables as the new screen came bare bones so had to move the sensor and display cable over to the new screen, I checked all the sockets etc and nothing of concern. I have ordered a display cable too if it turns out to not be the logic board. The system loads up fine on the external monitor with the fans on max so cannot see why it would not boot just the iMac screen being a 5k screen just like the external? My main concern when I first looked at the back of the origional iMac screen was the heat marks next to the display cable and another down by where the fan would be located? — Electric Wheels
@ewheel thanks for doing that. Can you do a straight down view of the board connectors and surrounding components? also, can you clear up the last two images and zoom in on the actual connector please? I am just following a hunch — oldturkey03

Dan @danj 声誉积分: 479.6千 Self employed contract worker 35 329 971 · Answer 1 · 2023-01-20T11:50:14-07:00

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Dan @danj

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发帖于: 2023年1月20日

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What does the onboard diagnostics tell you? Restart the system and press the D key to enter. Try without the external and if that fails try with the external connected.

Reference Mac startup key combinations

Let us know what you discover!

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Thank you for your response to my issue and I am not able to test this myself until I can collect the iMac from the shop after the weekend but the iMac does not respond to wired or wireless keyboard commands with the main screen connected when it has the boot chime loop and only works with the screen taken off and the iMac connected to an external monitor from what the shop told me but I cannot confirm this until I get my iMac back to see what the diagnostics led's show

由 Electric Wheels 完成的 2023年1月20日

@Electric Wheels - first see what the startup diags tell you before opening the system. The logic board diag LEDs wouldn’t tell you much.

由 Dan 完成的 2023年1月20日

Thank you Dan and the system has already been opened up in the IT shop, I asked them to leave the screen taped and not resealed so once I get the iMac back I will try the system diagnostics as you state but as before I will only be able to run it using the external monitor with the iMac screen disconnected from the logic board as it will boot chime loop and will not accept keyboard commands whilst the iMac screen is connected to the logic board. Once I get the iMac back after the weekend I will perform the diagnostic and post the results

由 Electric Wheels 完成的 2023年1月20日

@ewheel - What is the history of the system? Was it opened before this failure? I didn’t quite understand the need to disconnect the display fully. This aims me to a shorted T-CON board within the display assembly.

由 Dan 完成的 2023年1月20日

The system was owned by one person before me from new and has never been opened until now. The reason for disconnecting the main screen was to look inside for hardware faults as the machine was not booting and was just stuck in a boot chime loop, blank screen with no backlight or picture, keyboard commands did not work and nothing showed on external display. Once the main screen was removed the iMac will boot as normal but only to external display and if the main screen was put back in then we are back to the boot chime loop, no display on either iMac or external and no keyboard commands work. This is what the IT shop worker told me and said they cannot test anything further due to not having any 27” mid 2017 parts and it would cost me £600 for a screen if that was what was causing the issue and if it was not the screen then it could be the logic board but they would only fit parts that come directly from Apple, I told them to tape the screen whilst I source cheaper parts

由 Electric Wheels 完成的 2023年1月21日

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iMac Intel 27" Retina 5K Display (Mid 2017)

Is my 5k LCD Dead?

Update (01/24/2023)

Update (01/24/2023)

Update (01/25/2023)

Update (01/25/2023)

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