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Spindle Motor Control Circuit
The Spindle
Motor
Enable signal is input via J4, Pin 6, of the motor
control circuit board to gate the spindle motor current (Figure 4-10).
This current is controlled by an integrated regulator circuit when the
spindle
motor
is
enabled.
The
potentiator
provides an adjustable
D.
C.
voltage
reference
to the regulator circuit for spindle speed
adjustment.
The
tachometer
signal provides feedback from the motor
via
Pins 3 and 4 of Jl of the motor control circuit board to maintain
a constant speed of 300 RPM.
This signal is 12 volts A. C.
Diskette Enabled Switch (Door Lever)
with
power
applied
to
the
drive
unit and the motor enable false,
inserting
a
diskette into the drive and closing the door lever turns
on
the
motor
for
five
seconds.
This feature ensures the proper
clamping of the diskette to the spindle hub and the centering cone.
Motor control can be accomplished by drive select with WI installed.
ZZ
H
H
P< P<
\
/
Itn;;J[~
/
PIN 6
SPINDLE SPEED CONTROL
FIGURE 4-10
SERVO CIRCUIT BOARD
4-14
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