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A1418 / EMC 3069 / 2017 / 3.0 GHz quad-core i5, 3.4 GHz quad-core i5 or 3.6 GHz quad-core i7 Processor. Released June 8, 2017.

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Display shutting off on iMac randomly.

Hello all. Thanks for reading.

2017 iMac a1419 EMC 3069. Sat for 3 years, used to work fine. Upon poweringy it on, it works for a bit and then the display shuts off. Anywhere from 10 seconds to 5 minutes later. Rest of the computer stays working. No backlight or image that I could see with flashlight. When this happens, diagnostic lights 4 and 5 shut off.

Sometimes when booting, lights 4 and 5 never come on, and screen stays dark

I’ve tried replacing the blade ssd and hard drive, reseated all connectors, reseated CPU, etc.

I’ve tried an external monitor via usb-c to hdmi adapter, but it never works. I’ve wiped the drive, so I’m not getting to a login screen. I’ve heard that external will only work at login screen and after.

I’ve replace the NVRAM backup battery. Reset nvram, smc.

USB devices like keyboard and mouse work fine.

I’m trying to determine if it’s the lcd panel or the logic board. I’m quite proficient in electronic repairs, but I’ve not done much with Macs.

Any ideas? Thanks in advance.

Tom

Answer this question I have this problem too

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1 Answer

What happens when you plug in an external display? Does that work without problems.

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5 Comments:

I cannot get the external display to work. But I can’t rule it out since I’ve not gotten the computer to boot as far as a login screen. (I had wiped the hard drive in a diagnostic attempt, have not had the display working well enough to get osx installed.)

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@tbaker2220 - Using a second Mac create a bootable OS installer USB thumb drive so you can test things

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I have a usb drive set up as a bootable Mojave installer. I can see it on the internal lcd for as long as it stays on. Should I be able to see an external display also at that point?

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I verified on another Mac, the external screen doesn’t get signal until you get to an actual login screen. A recovery install drive doesn’t bring up an external screen. :-(

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tbaker will be eternally grateful.
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