Heads swap – HDD failure as an example WD1600JS

The main trouble the old WD – serious problems a specialist data recovery can come across when changing the  head assembly (heads swap). Chose the most compatible unit, which should fit on all the criteria, it is a good chance to get clicking drive upon heads swap.

So here, I tested the drive, troubleshoot 0-th head of heads map 0-1-4-5.  There is no central magnetic platter  in the package, and there are a pair of middle-heads on the block missing. Read a copy of the service area (SA) with the first head. Got a suitable donor, made a heads swap, supplied power – still clicking.

I began testing the heads one by one. Strange thing – individually all heads work fine, only under the SA 0-th head read with some errors. Do nothing, looking for another donor, this time to get the correct image of the RAM drive launched with the translator of the hard drive, which should share with me lost client files.

Did hot-swap and finally got access to the surface. I mapped the heads – that is calculated a correlation table between logical LBA sectors and physical sectors under the physical heads. I started to read data. Under the first head LBA can not be read at all, and when you try to address this head drive goes BUSY and “searches” heads (the sound of the constant repositioning heads).

And this is despite the fact that individually 1st head works fine. Not only read, but even writes without errors! So what is wrong? Why the drive with basically suitable and workable heads can not start on their own and in combination  heads did not work while separately operated just fine?

The fact that the drive at power makes test – through all of the head and trying to fit in the time-out search and servo sectors. Because of the displacement of the head relative to one another (in a donor head stack after replacement) the drive can not stand the time limit of the timeout and starts clicking. For this reason, the disc may not work with all the heads simultaneously, but can work with each one separately.

To succeed in this case is very difficult. Different experts use different methods, someone modifies the firmware to disable heads verification at the start of the disk, someone uses a calibration cycle to get the image of adjusting adaptives for the new heads stack.