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Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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macOS will not install or load from bootable USB drive

Hello All,

Bit of a strange one here, at least I think so.

I have just purchased an iMac 27” 2013 model, it was sold to me as not booting.
Fault finding process, Environmental, Hardware, Software or customer education, environmental and customer education ruled out.
On to software;
- used a known good version of 10.13.6 on a bootable Usb drive to boot the iMac - failed, normally this would prove software is not at fault, but there could be firmware issue if the iMac had a higher OS installed.
- Command R / internet recovery will not load

On to hardware;
- Hard drive ruled out due to software fault finding
- Ram ruled out, known good RAM installed still no change to fault
- NVRAM reset performed, no change to fault

Normally this would leave the logic board that would need to be replaced in order to get the iMac working, but here is the thing, the iMac loads into Ubuntu desktop from a bootable USB drive and using benchmarking tools I can confirm a working CPU and GPU.

What would cause a Mac not to work with macOS but to work just fine with other operating systems?

Thank you for your time.

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Have you tried using a bootable OS X Mavericks or MacOS Sierra bootable USB/CD?

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I haven't but if that were to work then the internet recovery should work, no?

I have never come across a Mac (that can run up to 10.15) have an issue with 10.13 but then work at 10.12 or lower.

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You are likely hitting two different issues!

Ubuntu messes with the Master boot blocks and boot loader of the drive so you can’t boot up under macOS.

So you will need to nuke the drive with Mac Disk Utility and properly install a fresh macOS.

But how?? You’ll need to boot up under an external bootable drive. I would start off with macOS 10.12.5 Sierra and the highest your system can officially run is macOS 10.15.x Catalina.

Using another Mac download from here the macOS you’ll need How to get old versions of macOS and for example follow this guide How to create a bootable macOS Sierra installer drive make sure the USB drive has been formatted with Disk Utility with a GUID partition map and a Journaled file system.

That should do it. If not leverage the Startup Manager using Option (⌥)

Reference: Mac startup key combinations

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I'm sorry but it looks like you didn't read my question, I had already ruled out the hard drive as the issue, please remove this as an answer.

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@Brendan Mills - Nope, I read it, in fact twice! This is the key: "the iMac loads into Ubuntu desktop from a bootable USB drive and using benchmarking tools I can confirm a working CPU and GPU."

So you've rolled out hardware fully! But you forgot about the drives files not the drive its self.

Think of it this way... これは無意味です makes no sense to you as its a different language. So a person speaking it is not failing its the lack of understanding!

Thats your issue here as the OS presently on the drive uses Master boot blocks Vs GUID (as it can be setup that way) to then add to the mystery the systems firmware can get in the way if its not been updated with the newer version that supports AFS

So you could have a double whammy! The answer is correct. Take the time to prove me wrong by fully reformatting your drive and installing Catalina. I think you've be surprised!

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