The external unit has two main parts: * a disk-drive * an adapter (USB-to-disk-drive) and either part can fail.
So, disassemble the unit, and remove the disk-drive, and connect it as a 'slave' drive in a desktop computer, to see if it works. If it does, it points to the adapter as the problem. See: http://www.canadaram.com/3_5_sata_enclosures.htm for examples of "empty' external enclosures into which you can 'transplant' your disk-drive.
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The external unit has two main parts:
* a disk-drive
* an adapter (USB-to-disk-drive)
and either part can fail.
So, disassemble the unit, and remove the disk-drive, and connect it as a 'slave' drive in a desktop computer, to see if it works. If it does, it points to the adapter as the problem.
See: http://www.canadaram.com/3_5_sata_enclosures.htm
for examples of "empty' external enclosures into which you can 'transplant' your disk-drive.