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SPINDLE ASSEMBLY
The spindle assembly is the physical inter-
face between a drive and a disk pack.
The
surface of the pack mounting plate (Figure
3-7)
~tes
directly with the center of the
disk pack.
A vertically free-floating lockshaft runs
through the center of the spindle assembly.
The upper end of the lockshaft contains
internal threads that engage the external
threads of a stud projecting from the disk
pack.
When the disk pack canister cover
handle is rotated clockwise, the spring-
loaded 10ckshaft is pulled upward and the
disk pack is pulled down.
As a result, the
mating surfaces of the disk pack and spindle
are engaged by a force of approximately
325
pounds.
When the disk pack is fully en-
gaged, a release mechanism in the canister
handle frees the canister from the disk pack.
The spindle is locked by the pack canister
when installing or removing a disk pack.
This makes it easier to install or remove
a disk pack by preventing spindle rotation.
The pack on switch and ground spring (Figure
3-7) are mounted at the lower end of the
spindle assembly.
The ground spring is
mounted so that it is
a~ways
in contact with •
the lockshaft to bleed off any accumulation
of static electricity on the spindle to the
deck through a ground strap.
The pack on
switch contacts transfer in response to the
DRIVE
~l'
' - T -
PACK SENSOR
SWITCH
8DI63A
Figure 3-7.
Spindle Assembly
83318200
A
vertical movement of the 10ckshaft.
When
the shaft is up (disk pack mounted), the
contacts are closed.
When a pack is not in-
stalled, the shaft moves downward to deflect
the switch actuator and transfer the con-
tacts.
The switch is part of the interlock
that inhibits spindle motor power to an
improperly configured unit.
ACTUATOR
The actuator consists of the carriage, actu-
ator housing, and magnet assembly.
The
actuator (Figure
3-8)
is the device that
supports and moves the read/write and track
servo heads.
The forward and reverse moves
of the carriage on the carriage track are
controlled by a servo signal.
The basic
signal is developed in the logic section and
processed by a power ampl.ifying stage in the
power supply.
The power amplifier output is
applied to the voice coil positioner (part
of carriage).
The signal causes a magnetic
field about the voice coil positioner. This
magnetic field reacts with the permanent
magnetic field existing around the magnet
assembly.
The reaction either draws the
voice coil into the permanent magnet field
or forces it away.
Signal polarity deter-
mines the direction of motidh, while signal
amplitude controls the acceleration of the
motion.
The voice coil positioner is a bobbin-wound
coil that is free to slide in and out of the
forward face of the magnet assembly.
Fastened
to the positioner is a head/arm receiver
which holds the 19 read/write heads and the
single track servo head.
The head/arm re-
ceiver mounts on the carriage and bearing
assembly that moves along the carriage track
on eight bearing type rollers.
Movement of
the positioner in or out of the magnetcauses
the same motion to be imparted to the entire
carriage assembly.
This linear motion is
the basis for positioning the read/write and
track servo heads to a particular track of
data on the disk pack.
(Refer to Head Load-
ing paragraph for detailed information on
read/write head loading and unloading.)
The positioning signal is derived in the
logic chassis and power supply.
The signal
is applied to the voice coil positioner via
two flexible, insulated, metal straps, the
ends of which are secured to the cam mount
and the carriage and bearing assembly.
During any Seek operation, the logic must be
informed of the current location and velocity
of the carriage.
This information is pro-
vided by the velocity transducer in the
magnet assembly and the lone track servo
head installed on the head/arm receiver.
The transducer is a two-piece device, one
piece stationary and the other movable. Refer
to the Transducers paragraph for a complete
description.
3-13
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