Due to an HDD failure, I have purchased and installed a new Seagate BarraCuda 1TB 3.5-Inch SATA III 6 Gb/s Internal Hard Drive (ST1000DM010)(https://www.amazon.ca/gp/product/B01LNJBA2I/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1).

The Mac is a 27" iMac EMC 2390.

When I boot using a System Install USB stick and launch Disk Utility, only the USB stick's device and partitions are visible. The unformatted HDD is nowhere to be seen.

The original drive was a 1TB Seagate; I see a slight discrepancy on the power specs, but not sure whether this has an impact.

Anything else I should try? At the moment I don't have any means to independently verify the integrity of the new drive (external Caddy etc).


Based on feedback here, I purchased an HDD caddy, which connected my new HDD to a working laptop via USB. I was able to mount and format the drive, and even proactively installed High Sierra on it. This at least confirmed the issue was not with the drive.

So then I proceeded to do a motherboard removal to get at the SATA cables behind it. I did not find any issues with the cables, but removed them, blew in them to clean them out, and reseated them before reassembly.

Upon reassembly, the computer recognized the drive and booted at once into High Sierra - success!

The process was relatively painless, though not complete free of issues: I snapped a fan housing (when I dropped the fan), which had to be epoxied, and I busted the JST connector for the skin sensor 2-wire cable, which I managed to hardwire upon reassembly. Now, although the Mac works, the fans are on full-speed all of the time, making it sound like an industrial shop vac and pretty much useless in the office environment. Live and learn.

  • I'd be tempted to suspect the SATA cable... but only way I know to test that theory is with a new cable, or try the drive in an external enclosure. [That may have been the root cause of the initial drive fail too] – Tetsujin Nov 10 '17 at 20:18
  • I hear you @Tetsujin about the SAT cable, though 2 things concern me: 1) the failure was mechanical (internal to the old HDD) and 2) that cable is pretty isolated within the body of the iMac - there's just no "wear" on it - I inspected the cable and it "appears" fine - I don't see what could cause a cable failure on a Mac that has been closed since 2010... – Tom Auger Nov 10 '17 at 20:20
  • Which version of macOS or OS X were you trying to install? Also, did you try executing the command diskutil list from the Terminal when booted from the USB stick? If so, what was the result? I am mostly interested if disk0 appears. – David Anderson Nov 11 '17 at 3:27
  • Thank you @DavidAnderson - I hadn't considered the command line. I will do that when I'm in the office on Monday. I was trying to install High Sierra, since that was the easiest to create a boot drive for (given that it's currently up on the App Store). – Tom Auger Nov 12 '17 at 17:00
  • Based on the edit - this might help with the fan issue. I've been there breaking delicate cables and needing to think about more parts or repairing them. apple.stackexchange.com/questions/66004/… – bmike Dec 6 '17 at 22:57

If you place a totally uninitialized drive on macOS - it not only shows in Disk Utility and lets you partition it, but it prompts you to format the drive for use.

Something else is up in terms of firmware, cabling or perhaps settings on the drive itself. If Seagate tech support doesn’t have some obvious things to check - you’ll want to test it in another computer or on an external sled to be sure it’s working before returning it to the vendor.

Chances are it’s a cable that needs reseating on the logic board or on the drive itself. I know reseating the non drive end of the cable is a pain and replacing the internal SATA cable is a big pain - so try to test externally first if you can.

You probably know all the above since you mentioned independently verifying so here are some last ditch things:

  1. Reset the NVRAM on the iMac (command option P R at boot)
  2. Reset the SMC on the iMac (power down - disconect all power for 15 seconds)
  • Thanks @bmike for the advice. Your second opinion confirms what I was hoping to avoid. I'm going to pick up a sled so I can externally mount the drive to make sure it's not faulty while it's still under warranty. I don't see any dip switches or jumpers on the drive so I don't think there's much I can do in terms of the hardware itself. As a last step (because of the effort), I'll try to gain access to the logic board side of the SATA cables and see if there's anything going on there. Sigh. At the end of the day, sometimes this DIY repair business is more trouble than it's worth! – Tom Auger Nov 11 '17 at 14:38
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    For several years I workied on these iMac, @TomAuger - we almost never had to replace the cables. We did go to the trouble to disconnect them - re/place the routing and then firmly reconnect them. That fixed almost all cases. Also, the drive surely has software configuration switches now as opposed to jumpers from the old days. Forgive the nostalgic suggestion there. The vendor will surely confirm you are plug and play if so. – bmike Nov 11 '17 at 15:08
  • Didn't find anything wrong with the cables but after removing, dusting and re-seating the drive is now being recognized and works great. Thanks for the encouragement! – Tom Auger Dec 6 '17 at 22:55

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