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3-13.
DISC DRIVE PCA-A1
The Disc Drive PCA-AI consists of a mechanical
assembly and three printed circuit boards (see
figures 3-3 and 3-4).
3-14.
D:RIVE MECHANICS
The mechanical portion of the disc drive consists
of a die-cast frame and a Head/Disc Assembly
[HDA]. The HDA is suspended within the frame on
shock isolators/absorbers. This method of construc-
tion protects the HDA from mechanical shock and
stresses associated with mounting the drive in a
system enclosure.
Theory Of Operation
7957/7958
The HDA consists of a die-cast base, sealed to
form a clean area that contains virtually all the
drive's mechanical components. Air is circulated
through the clean area by disc-rotation induced
flow. The circulating air is passed through a filter.
For pressure equalization, the clean area "breathes"
to the outside via another filter.
Inside the clean area are three or five magnetic
discs (depending on the model); the servo head and
from five or eight recording heads (again, depend-
ing on the model); and the rotary voice-coil
positioner. The surface of the disc that is nearest
the die-cast base is used for servo track informa-
tion. The discs are driven by a direct-coupled
brushless DC motor which mounts on the outside
r---------------------------------------------,
DISC DRIVE ASSEMBLY (HDA)
PCA-A1
r ---------------------------,
I
MECHANICS ASSEMBLY *
•
•
(
- 7
_6
(
- 5
PREAMP
_4
POSITIONER
(
PCA
- 3
_2
(
-,
_0
(
-S
rt
BRAKE/LATCH
I
)
)
)
J
)
SPINDLE
B
HDA
J4
GROUND
LUG
L. _____
------
1---------
------
.J
~
-
DRIVE
SPINDLE
ELECTRONICS
MOTOR
PCA
T
-
I
I
J
J7
I
I
J6
I
I
J5
L
I
-
I
MOTOR CONTROL PCA
-
• HP7958A - 5 DISCS. 8 R/W HEADS.
I
22
HP7957A - 3 DISCS, 5 R/W HEADS.
I
J3
POWER
--------~-----~-~---------
-----
Figure 3-3. DISC Dnve Assembly PCA-AI Block Diagram
______ J
3-7
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