Today I have got a rattling hard disc Western Digital vol. 20 Gb for information recovery. The client is a photographic studio. The disk contains the program controlling all processes of film development and photos printing device. At power on the engine is accelerated and then even tapping inside the hermetical unit starts. Similar symptoms can be caused by several reasons, but in the given case the sound character unequivocally specified the problem inside the hermetical zone. I prepare a clean room (switch fans of air clearing system on), and my "patient" is on the "operating table".
Particularly these discs models have one unpleasant feature as heads assembly fastening design. The matter is that this range of discs was created as budgetary; consequently, the price was reduced. And instead of being fastened to solid arms and rests, MHA is not fixed along its axis and is fixed to the top cover of the HDD case with the screw. Thus, a simple cover removal in any case will lead to microdisplacement of the head assembly, which differs from the factory position. Just remove and put back a unit top cover, and your disc is dead. There are special techniques as cover clip force and skews over tension control for elimination of possible problems with the head assembly position.
At opening the failure reason becomes obvious.
The MHA plastic rest was broken, and heads lost the stop. Being switched off, heads took off the plate limits, and at the subsequent power on they tried to go back on the disc, and heads mr-elements were just torn from holders, and the holders were bent.
Fortunately, mis-shapen holders did not damage plate coating seriously though particles of destroyed heads are visible on the magnetic clamp together with the stop fragment.
Therefore the interior of hermetical zone is to be cleaned carefully of all damaged MHA metal particles in order to prevent possible injure of plates at the data recovery process.
The client learns the approximate cost of information recovery, and he is informed on necessity to pay the donor disc from which the serviceable heads assembly will be removed. Having received consent, I start to act. A suitable donor disc is found at my store, as it has been carefully bought beforehand. As I have already mentioned, a good part of obtained money constantly is spent on purchase of serviceable and faulty discs, for updating spare parts. If a disc model range disappears from of shops counters, in case of need it becomes extremely problematic to get a necessary disc.
Criteria of heads compatibility on WD storage discs are defined on a lot of parameters. It is hard to fit a head on the faulty storage disc. And there can be problems even with compatible heads. In this case, despite of compatibility by choice criteria, the disk "refuses" to display readiness independently, after the head assembly is replaced. To get access to working area I have to make image of correctly loaded microprogram in view of the damaged storage logic translation, and to load this image directly in the RAM of printed circuit board. Then the disk has given access to LBA and therefore, to the user data.