Information recovery from faulty WD1600AAJS storage disc is required. At power on the motor is not accelerated.
Dismantling of the printed circuit board reveals the initial diagnosis - failure of spindle motor control chip and head assembly positioning unit. It is necessary to notice, that printed circuit board design of Western Digital HDD since they were Caviar 20 Gb has the same unpleasant feature - circuit technique practically has no protection against a poor-quality power. Therefore, in cases of power unit thyristor breakdowns usually power chips burn out and quite often CPU fails.
And if microcircuits fail and thermal injury is visually noticeable, usually a preamplifier/commutation chip in the hermetical zone fails. For information recovery from the Western Digital HDD with such a malfunction it is necessary to repair or change a printed circuit board. A simple PCB change is not enough as microprogram correction to adapt a new PCB to the necessary hermetical unit is needed.
The head assembly replacement on these disks is not of special complexity - heads are placed on the parking racks. But it is rather hard to find a fitting donor disc. There are a lot of head assembly unit and switchboards models so it is necessary to know, what features are to be taken into account at the choice of a donor disc.
One more moment in these discs design is a peculiarity of head assembly fastening to the case. It differs from more serious approach and fastening method in the discs of other manufacturers where the unit is fastened on the axis with a screw, a clip and then the top cover is screwed to the axis, at WD1600AAJS all is made according to a cheaper budget. The unit is fastened on the axis freer, with small gaps, and is tightened with the top cover bolt. Therefore after a suitable head assembly installation it is necessary to select a hermetical zone cover screws tension experimentally to provide the head assembly optimal position on the axis.