The positioner servo electronics comprise a major functional block. As the disk rotates
at
a fixed speed, and the recording heads are flown over the disk surface, the positioner is
controlled
In
both the velocity and position modes. The positioner moves
to
the correct
address under control
of
the pOSitioner servo control electronics. Data are then written on
the desired surface by selecting the corresponding
head
through the
head
select network.
The
read
/write electronics are subdivided into three functional blocks consisting of the
head
select network, the write electronics, and the read channel. Write data causes write
current to
be
switched according to the pulse train on the
WRITE
DATA SIGNAL line.
The
storage
surfac~
will then
be
magnetized accordingly.
During retrieval
of
the stored data, the corresponding head
is
again selected by the
head
select network and the signal obtained from the read/write head Is processed
by
the
read
channel Into separate
READ
DATA and
READ
CLOCK Signals for transmission via the
interface. The particular segment
of
the disk which Is pasSing under the read/write
head
is
specified by the sector pulse and sector count lines from the sector electronics.
Control of the rotational speed
of
the disk is accomplished by the speed control
electronics group which establishes a known, fixed speed
for
the disk rotation within ± 1
percent
speed
tolerance. The sector electronics block provides pulses at the Interface
which electrically subdivides the disk
Into a number
of
sectors for the purpose
of
addressing data stored on the disk. Figure 1·5 Illustrates the subdiviSion
of
a platter Into 8
sectors by means
of
mechanical sectoring.
The air system consists
of
an
absolute filter preceded by a pre.fllter, and a blower driven
by the same motor which provides drive
to
the disk spindle. This air system provides a
well-filtered flow
of
clean air in the disk area to remove contaminants.
Power to the various electronic circuits
Is provided by
an
integral power supply. This
power provides dc voltages at suitable levels derived from the
line voltage.
All major components are mounted to the base assembly. An aluminum alloy casting
Is
the basic component of the base assembly. Mounted onto the casting is the drive
mechanism'which consists
of
a precision spindle,
an
ac Induction drive motor, a squirrel
cage blower, and
an
idler system. Power
to
rotate the blower and spindle
is
transmitted
from the drive motor by means
of
a flat belt. The Idler system provides constant tension
of
the belt and compensates for stretch
of
the belt.
SECTOR
SLOT
INDEX
SLOT
TOP
VIEW
Figure 1-5. Mechanical Sectoring
1-~
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