Theory of Device Operation
4-2C141-E088-01EN
4.1 Outline
This chapter consists of two parts. First part (Section 4.2) explains mechanical
assemblies of the disk drive. Second part (Sections 4.3 through 4.7) explains a
servo information recorded in the disk drive and drive control method.
4.2 Subassemblies
The disk drive consists of a disk enclosure (DE) and printed circuit assembly
(PCA).
The DE contains all movable parts in the disk drive, including the disk, spindle,
actuator, read/write head, and air filter. For details, see Subsections 4.2.1 to 4.2.5.
The PCA contains the control circuits for the disk drive. The disk drive has one
PCA. For details, see Sections 4.3.

4.2.1 Disk

The DE contains disks with an outer diameter of 65 mm and an inner diameter of
20 mm. The MHJ2181AT have three disks and MHK2120AT and MHK2090AT
have two disks and MHK2060AT have one disk.
The head contacts the disk each time the disk rotation stops; the life of the disk is
50,000 contacts or more. Servo data is recorded on top disk.
Servo data is recorded on each cylinder (total 66). Servo data written at factory is
read out by the read/write head. For servo data, see Section 4.7.

4.2.2 Head

Figure 4.1 shows the read/write head structures. MHJ2181AT has 6 read/write
heads and MHK2120AT has 4 read/write heads and MHK2090AT has 3
read/write heads and MHK2060AT has 2 read/write head. These heads are raised
from the disk surface as the spindle motor the rated rotation speed.