About Guides FAQs

Change Font Size

Change Screen

Change Profile

Change Layouts

Change Menu Styles

Apply Reset
Cpanel
Quick Menu

Mechanics

The whole construction is based on the drive case protecting sensitive mechanical parts from environmental influence. Inside it is filled with dust-free air though the air is not specifically purified; instead the assembly of the mechanical part is performed in a special workshop where air contains less than one hundred dust particles per cubic meter, i.e. in the so-called "class 100 clean room".
HDA case has an opening blocked by a tight air filter. It is used to align air pressure inside the HDD and outside. Unfortunately, if a drive falls into water, the latter penetrates the inner space through that opening. Rotation of disks creates air flow circulating inside the case and constantly passes through one more filter separating dust if it somehow appears inside.
Drive case accommodates a pack of magnetic disks driven by a spindle motor, magnetic heads with their positioning system and a preamplifier/commutator enhancing the signal from the heads and switching between them.
A magnetic disk is a circular aluminum (rarely ceramic or made of special glass) plate with surface polished in accordance with the highest precision class for the sole exception of the parking zone, if it is present. In fact, high precision of disk surfaces and the heads causes them to "stick" to each other because of molecular attraction forces. To prevent that effect, manufacturers use special laser serrations in the zone of contact between drive heads and disks.
The disks demonstrate specific magnetic properties owing to their chrome oxide based coating (magnetically active substance) or cobalt layer applied using vacuum deposition. Such coating is characterized by high hardness and much greater wear resistance compared to previous models coated with a layer of soft varnish based on ferric oxides which could be easily damaged unlike modern coatings.
The disks are rotated by a special 3-phase electric motor. The stationary part contains three windings connected according to the "star" scheme, with a tap in the middle, and the rotating part is a permanent sectional magnet made of rare-earth metals. The requirement of beat reduction and high rotational speed values force the manufacturers to use special bearings in the spindle motor; these can be either ball bearings or improved fluid bearings (using special oil dampening impact loads and thus increasing motor durability). Fluid bearings are characterized by a lower noise level and produce practically no heat during operation. The number of revolutions per minute in modern IDE drives is equal to 5400 RPM or 7200 RPM; for modern SCSI drives it is 10000 RPM or 15000 RPM.
A magnetic head is also a sophisticated construction composed of numerous details. Those details are so small that they are manufactured using photolithography method just like chips. Working surface of the head's ceramic case is polished with the same precision as the disk itself. Heads' actuator is a flat solenoid coil of copper wire suspended between the poles of a permanent magnet and fixed at one end of a lever rotating around a bearing. The other end of the lever is connected to a bracket carrying magnetic heads. The bracket is spring-loaded with a certain effort which allows the heads to "fly" at a definite height above the disk surface; the said height is usually equal to tenths of micron.
The whole transport system moving the heads' pack has been called Voice Coil by analogy with a loud-speaker cone. Its functional principle is similar to that of a common dynamic loud-speaker (i.e. copper coil in static magnetic field). Positioner's coil is surrounded by a stator acting as a permanent magnet. When electric current of certain voltage and polarity appears in the coil the positioner starts turning to the corresponding side with respective acceleration; thus dynamic modification of current properties in coil allows positioning of magnetic heads to any location above disk surface.
Drive heads are fixed when a drive is powered-off (in the parking zone) with special latches. Magnetic and pneumatic latches are two most widely used types. A magnetic latch is a small permanent magnet fixed within drive case and attracting ferrous lug on the voice coil in the heads' parking position. Pneumatic latch (or air lock) also fixes a positioner in the parking zone preventing its further movement. When the magnetic disks begin rotation the air flow thus generated deflects the "sail" of an air latch and unblocks the positioning system.
The electronic components inside HDA are limited to the preamplifier/commutator for the signal received from drive heads. It is located closer to the heads to minimize interference of external noise, right over the flexible cable from the heads to drive's electronics. The same cable is connected to the voice coil and, sometimes, to the spindle motor; however, in most cases power supply of the spindle motor is implemented via a separate cable.
A HDA is usually linked to the PCB with two connectors. One of them is a three-phase center-tapped connector for the spindle motor while the other delivers signals from the preamplifier/commutator and voice coil.

Contatti:

        Modulo di Richiesta         e_mail

I Nostri Clienti

Array Array Array Array Array Array

Chi siamo

Join in

Contatti

Chi Siamo

Sample imageUniDataRecovery, Una delle aziende Leader nel campo del Recupero Dati, con sede a Londra e con filiali in Europa, fornisce supporto a tutti i clienti internazionali, dalla piccola e media impresa fino a società quotate in borsa.