A friend of mine brought a disk that wouldn't work when connected to a machine.
As soon as I hooked the disk to my box, it restarted and refused to start, with all lights blinking madly. Seems like a short-circuit caused that to heappen, so I replaced his case and put the disk in my case and this time: No short-circuit.
The OS booted, but running "lsusb" command showed nothing on the USB bus. When I replaced the case, the pins of his disk interface were a bit bent and I had to straighten them to be able to hook my case's PATA-to-USB (PATA = Parallel ATA) interface.
So, I thought, maybe the controller board itself, which has the PATA interface is damaged somewhere. Lucky for him, I had a disk of the same brand & model number, so I took mine out and put it on his disk. After doing that, I hooked it to the USB port on my machine, and still nothing on the USB bus.
After all easy & safe attempts were futile, the next step was to open the disk's case and look inside at what's really going on. During the previous attempts, I could hear a tiny sound of an attempt to read then failure, so hopefully now I'd be able to inspect further more.
After unscrewing all these tiny pesky screws with proper tools, it turned out that the disk's mechanical head was jammed. I tried nudging it and moving it with the screwdriver, but it seems it was stuck for good. This means, the whole disk housing is useless now, and the only way to get the data is by moving the disks from one hard disk to another. This was much tougher than I had anticipated and took me around 2 hours to carefully move the parts.
The disk heads rest at the edge of the disk, barely touching it, but they don't allow you to take the disks out. In order to do that, there's a white plastic piece, which has grooves where disks lay in, that should be removed first, in order to properly remove the disks. The heads, also partially rest on this plastic piece, and to take the piece out without damaging the heads, the heads must be moved to the inner-side of the disks -- This is by no means an easy task!!!
Pushing the heads by finger also got them bent. To be exact: The heads have small buds that hang by a very tiny piece of wire. These buds are the parts that touch the disks and read/write the data; the heads only work on moving these buds around the disks while the disks spin. I pushed one of the buds a bit to the top, to be able to push the heads safely to the inner part of the disk -- This was a major mistake. Pushing the bud inside rendered it dead and MY disk was no longer readable!!!
So, the whole salvation operation failed and resulted in 2 deaths. The only thing gained from this was experience on how to deal with these in the future, and the fact that I need a magnifier to be able to deal with the heads.
I should mention that I got my screwdrivers from: Al-Nisif warehouse, in Canada-Dry street, Shuwaikh. I'll get their exact info later.
Below are pictures I took while performing the operation.