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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My iMac won't recognize an external hard drive, but 3 other macs will.

I just bought a 3TB Toshiba external hard drive, and when formatting for mac it on my iMac it was getting an error when I named the drive in Disk Utility. I brought the drive to work and formatted it there (leaving it as untitled allowed it to be formatted).

After working on it all day when I brought it home to my iMac it was no longer showing up in Disk Utility. The light turns on and it sounds to be working. I plugged it into my laptop and it shows up right away.

I believe I might have done something to mess it up just on my personal computer that isn't recognizing it anymore. I hope this makes sense.

Answer this question I have this problem too

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What is the drive's connection: USB-A or USB-C or Thunderbolt?

Also, what are your other systems? Mac's or something else and the OS version.


USB-A I formatted the drive on an iMac running Sierra 10.12.6, and it works on my macbook pro running the same. The iMac it's not working on is also the same.

I am worried something must have happened the first time I tried to format it at home, and now it won't show up at all.


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1 Answer

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I don't see your formatting as being the issue as all your systems are the same MacOS.

I'm thinking you have a power type of issue with your system. Are you using the same USB cable? If you are you'll need to get a USB power meter to test across your different systems. IFIXIT offers one but it's out of stock: USB Mini Voltmeter.

Using it you should be able to compare the voltage and current draw between your systems. Let us know what you find.

USB Mini Voltmeter Image


USB Mini Voltmeter


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