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모델 A1419 / EMC 2806 / Late 2014 또는 Mid 2015. 3.3 또는 3.5 GHz Core i5 또는 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 또는 3.5 GHz Core i5 또는 4.0 GHz Core i7 (iMac17,1) 모두 Retina 5K 화면 장착

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Apple mac won't power on.

Using the Mac as I normally do then rebooted it into bootcamp.

  • Display just showed faint glow and sat there.
  • Hard reset it. Exactly the same.
  • Reset nvram and pram. Still the same.
  • Safe mode boot. The same
  • Network boot. Recovery. Diagnistic boots all the same.

Internal board LED diagnostics

Computer off

  • 1 on
  • 2 off
  • 3 off
  • 4 off

Power on

  • 1 on
  • Followed by 2 on
  • Followed by 3 on
  • Followed by 4 on
  • All 4 on
  • 3-4 seconds later 4 goes off.

Unplugged, cleaned and reseated display. Still the same.

  • Checked main board with thermal camera. All OK. No hotspots.
  • Fan on idle.

Any answers or what to check.

Need to use my computer urgently.

Cheers

Mac

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the only things that could work that you haven't already done is checking the connectors and replacing parts though there is a list of guides on how to replace the various different parts iMac Intel 27" Retina 5K Display (Late 2014 & 2015)

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What is your drive setup? Fusion, SATA HDD or blade SSD or did you change the drive out.

The onboard diagnostics are reacting normally so the logic board is doing what’s expected. That aims us to the drives and the low level and OS held on them.

Do you have a macOS bootable external drive to startup the system? You’ll need that and ideally the same version of OS your system is currently running.

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Fusion drive failed years ago. Replaced with ssd.

Current ssd changed last year.

Old one put in. Exactly the same. 4 lights in order. 4th goes out.

So not ssd failure. (It was same os on the old disk)

I'll have a look later. Off to get the mini m4 pro.

@theridgeback - To be clear you swapped out the blade SSD or did you swapout the SATA HDD to a SATA SSD?

As this was a Fusion Drive’d system you really need to pull the blade SSD as you really don’t want it still in there if it’s dead or not used.

It was the blade that failed. So I removed both drives (bit of a ball ache) and put in a standard ssd. That was probably 2018. I upgraded the old ssd last year to 2TB as the wife wanted windows on it and couldn't be bothered to dejunk it for space. I still used the old drive to ocasionaly externally boot from it as well.

@theridgeback - using that external are you able to boot up? You’ll need to engage the Startup boot disk manager Option (⌥) as described here Mac startup key combinations

Nope. Tried all of that. No safe mode

No diagnostics. No network boot. No boot select using option key. Nada.

I've tried everything that a normal person would try.

The only thing I have not tried is verbose. But as the screen isn't working it's pretty pointless.

One other thing to mention.

There is no chime on any of the boot attempts.

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