Four months ago I bought an external SATA case with USB-C compatibility so I can install my iMac OS there, did this because my iMac has built in HDD and was so slowww..

With the case I started using an ADATA 120GB SSD and everything worked like a charm for the past months, up to now...

As an extra fact I have to say 1 day ago I took the computer to another location (car trip) used like 12 hours and take it back to my office (of course I unplugged the SSD and plugged it back a couple of times), this was the first time EVER I unplugged the SSD case.

Today I was working as usual and the computer suddenly turned off and showed a message like this:

enter image description here

So waited for the iMac to restart and continue working, the message appeared 3 times after 20 minutes aprox of working.

The fourth time the message appeared I tried to start up again and the OS didnt started. The apple logo appears up to the loading bar but it turns off at 30% more or less.

This apple logo thing only happens when starting up from the external SSD, if I boot up from the default HDD it works good (I didnt remove the OS from there cause I knew something like this could happen).

So I would like to know what do you thing could go wrong? Maybe the USB-C cable got damaged in the trip yesterday, or its just that the VANTEC case is not supporting this kind of usage, or even the SSD?

I cant use the iMac with the OS running at the HDD, I've get used to SSD speeds both in my iMac and macbook so I would like to solve this problem fast cause iMac is my principal work station.

The drive enclosure is: VANTEC ENCLOSURE

The SSD is (120GB version): ADATA SSD

If I buy a brand new samsung external SSD, can I expect similar issues?

Thank you so much, I would love to hear what you think about all of this!

  • That screenshot is of a Kernel Panic. Looks up Kernel Panics and the causes of repeated ones if your quest to find a solution.
    – njboot
    Sep 16, 2018 at 3:36
  • Try clearing your NVRAM. Hold Command-Opton-P-R and turn on your Mac while doing so. If that doesn't help, try safe mode. Hold Shift while booting.
    – Joseph
    Sep 16, 2018 at 4:51
  • Also, try using verbose mode and taking a video of the boot. Hold Command-V while turning it on until the screen turns on with white text. Take a video until it fails, then review the footage and take screenshots of the messages immediately leading the KP. Edit your question with those.
    – Joseph
    Sep 16, 2018 at 4:56
  • Not answer, but sth to consider: if you buy a brand new SSD, you should really try to figure out to install it internally. Sep 20, 2018 at 13:58

2 Answers 2


If it worked fine for several months then I would suggest the case supports it. It's very possible that the control board inside the case or the cable is damaged.

If you have the technical know how, I would suggest placing the SSD inside the iMac. That way you also avoid the bottleneck of having to go over USB. There are plenty of online guides on how to do this.

I have used several of the MacSales kits, all the iMacs are still running and it took me 30 minutes at most.


There cold be several things causing this. However you will need to use the process of elimination in order to narrow down the root cause of this. Here are a few things you should try first.

  1. Try a new usb cable. Usb cables can go bad easily and defective cables can cause kernel panics and hardware issues on your mac. If using a new usb cable does nothing, it may be a bigger issue including a possibly failing hard drive enclosure, or SSD hard drive itself.
  2. To eliminate the possibility of a software issue (corrupt kernel extension, or start up apps, etc.), try using a Mac OS bootable install USB to completely reinstall Mac OS over the existing version on your SSD drive. But first, try repairing your hard drive in disk utility from the bootable usb installer screen. Then, in order to preserve your data, DO NOT format or erase your SSD in disk utility before hand. Just reinstall mac os over the existing software without making any modifications to the existing partitions.
  3. Completely format your SSD using your Mac OS bootable install usb, and try reinstalling everything from scratch. Be sure to back up your files before doing this. Formatting your SSD will erase everything on it.
  4. Report back here after trying these things.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .