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I have EEB-40S-U3 with 500GB Seagate Momentus inside and 2012 MacBook Air 13". When I connect HDD case to laptop nothing happens: I don't hear any sound from HDD itself, volumes does not appear in Disk Utility.app, nothing changes in USB section in System Information.app and no new lines appear in system.log. I suspect that MacBook Air just does not supply enough power for drive. What are the possible solutions?

Case and drive itself work fine with old ASUS X51L laptop, which supports only USB 2.0. I also tried to connect case via USB 2.0 cable, but that didn't help.

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  • If you open System Information and look at the USB device tree, is the volume sensed or does the USB just show the connected control chip or perhaps something less than a full entry? It's possible the drive isn't spinning up due to low voltage or low current from the Air. A twin tail USB cable often helps with hard drives that won't spin up by letting you get more power from a second USB socket.
    – bmike ♦
    Commented Jan 3, 2013 at 18:12
  • No, System Information doesn't show even control chip, just like nothing connected at all. Unfortunately, I don't have twin-tail USB 3.0 cable with this connector: en.wikipedia.org/wiki/File:Connector_USB_3_IMGP6033_wp_.jpg
    – imax
    Commented Jan 3, 2013 at 18:28
  • Yikes - of all the drives I've seen that needed a twin tail cord to work, at least something showed up in the profiler. If you can't sense anything with that cord, you'll need to isolate the issue to the Mac's port, the cable or the drive. Sometimes a faulty device will work with most computers but not all due to a hardware issue.
    – bmike ♦
    Commented Jan 3, 2013 at 19:14
  • Tried both ports on my and my girlfriend's Airs - doesn't work. But with ASUS X51L (laptop) and ASUS RT-N16 (wi-fi router) works just fine.
    – imax
    Commented Jan 3, 2013 at 19:19
  • If two Air don't power the same drive, you might need to talk to the drive manufacturer. MacBook Air can power a SuperDrive that triggers a high power mode on the USB ports, so they can push well over 950 mA to burn a DVD. Basically, it's unlikely two MAcBook are are both under-powering one hard drive and more likely the drive only asks for 500 mA and that's not enough to power it's controller.
    – bmike ♦
    Commented Jan 3, 2013 at 19:25

2 Answers 2

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If two Air don't power the same drive and you've tried several cables, you might need to talk to the drive manufacturer. MacBook Air can power a SuperDrive that triggers a high power mode on the USB ports, and I have seen reports that they can push well over 950 mA to burn a DVD.

Basically, it's unlikely two MAcBook are are both under-powering one hard drive and more likely the drive only asks for 500 mA and that's not enough to power the drive's controller or perhaps that drive/controller is simply out of spec.

You can refer to Apple's KB article that covers USB 3 devices getting 900 mA at 5V as a feature of the MacBook Air, so that should be plenty of power for a drive to operate.

You might need to seek service for either the Air or the drive if you can't fix things with trying other cables. The operation with other devices is nice, but in the end, if you need it to work with the Air, you'll need to work through that by repair/replacement of something.

Using the System Information tool on OS X, you should be able to determine if the USB chipset is sending any data over to the Air - whether or not it is getting enough power or even getting to the point where it can signal how much power it would like as part of the USB enumeration process.

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  • USB Prober does not show any changes when plugging/unplugging case. I've tried to use micro-usb 2.0 cable, but the only thing that changes is small LED on case near USB connector lights up.
    – imax
    Commented Jan 4, 2013 at 7:21
  • Wow - you've done about all the tests I can think of. Sometimes a certain chipset just doesn't work with another - but I can't tell from the product web page what internal controller that EEB device uses. Perhaps they spec several parts?
    – bmike ♦
    Commented Jan 4, 2013 at 13:46
  • Product ID: 0x0731 Vendor ID: 0x05e3 I can see this IDs when case is empty.
    – imax
    Commented Jan 7, 2013 at 14:51
  • Wait - so now it shows up in system information as a USB device?
    – bmike ♦
    Commented Jan 7, 2013 at 15:01
  • Empty case - yes, but not case with drive inside.
    – imax
    Commented Jan 7, 2013 at 15:12
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If your MacBook Air is a USB 3.0 version, then you have 900mAH our of your USB 3.0 port which can power up most of the 2.5" HDD 5400rpm or 7200 rpm. I have Toshiba that needs 1A, Hitachi needs 700 mah, WD, 550 mah. Most likely, you can power up Hitachi and WD.

If your MacBook Air is USB 2.0 version, then you will need two cable since each port only provide 500 mah.

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  • What is mAH do you mean milliwatts = mW ?
    – mmmmmm
    Commented Jun 2, 2013 at 8:23

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