Macintosh OS/Hard Drive


I have a MacBook Air, from 2011, now version 10.7.5.

I have never had any problem with external hard drives, but a little while ago one 1TB drive would not be read and I would get this message:

"Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled. To prevent damaging your computer, the USB device drawing too much power has been disabled. Other devices may have also been disabled. When you disconnect the device drawing too much power, your other USB devices will be enabled again."

I made sure the computer was plugged in, took all other devices out, closed all applications, and no change. Additionally the external hard drive would not vibrate or light up and not show up in disk utility. However, the drive was fine and could be used in other computers. Also, other 1TB drives could be used in this laptop.

In doing internet research, I decided to do an SMC reset (I also was having poor battery power so the symptoms fit). The HD in question worked for some time but now has stopped altogether, no matter what I do, and with additional SMC resets.

Any advice or thoughts on what is going on?

Some computer problems have symptoms like a light bulb, burnt out or not.
Some are similar to a lint trap in a drier, slowly worse over time.

Some hard drives require more power to spin up at startup, the power required can increase over time.  All hard drives die, they should be tested and repaired with Disk Utility or optimally with DiskWarrior. [this is dealing only with the directory, not disk surface defects]
Hard drives die mechanically, electronically, surface degradation, and logical errors.

External drive cases can be well built or not. A bus powered case is the worst choice available.
Putting a high power spin up drive in it, well, makes it worse.
OWC is my choice for storage on Macs (and PCs)

External USB hubs can have external power cubes or not, unpowered USB hubs are a poor choice.

Desktop computers often do not supply the same power level to front USB ports as the USB ports on the motherboard or a USB PCI card.

Laptops can have a single USB bus with several ports or multiple buses with a single port on each. Some have a simple electronic device that can be blown by too much current and will not deliver power at all, or very low power. Often you will see a device that has a Y adapter cable that allows it to draw power from TWO USB ports, there is a reason for this.

GOOGLE "usb port power output"   for your laptop specifications.

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David Anders


Seattle - The Computer Guy - 15 yr veteran Mac/PC/network problem solving. Clients are design firms, artists, freelancers and photographers. PLEASE PLEASE provide EXACT info for Mac Model and OS Version. RAM installed - added cards - external devices - recent changes. Do you do MONTHLY MAINTENANCE? With what Utility? What you have tried and what result do you want.


First computer experience 1969. Worked in 3 computer stores. Setup First Mac and First IBM-PC.

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