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CIRCUIT DESCRIPTION
Tracking and sled servo system
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ip
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>
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0.047
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22K
10K oe
(8)
(0.03
This block diagram is of the tracking and sled servo system.
The capacitor connected between
pins 8 and 9 determines
the time constant for attenuating the high-frequency gain.
The peak frequency for the tracking phase compensation
is
inversely proportional to the resistance connected to pin 17,
and the frequency is about 1.2 kHz when
the resistance is
510 k-ohms.
A FWD or REV tracking jump is performed by switching TM3
or TM4
ON. At this time, the peak voltage applied to the
tracking coil depends on the current at TM3 or TM4 and the
feedback resistance through pin 12, as shown by the follow-
ing equation:
Track jump
peak voltage =
back resistance
A FWD
or REV sled kick is performed by switching TM®5 or
TM6
ON. At this time, the peak voltage applied to the sled
TM3
(TM4)
current x Feed-
Ifo
680K
too
sa
A
TRACKING
PHASE
10K | 90K
1)
COIL
ICOMPENSATOR int
a
wo
66P
120K
9-22)
eis
+ G
100K
Cx
Ory
S STOP
<I
$ STOP
100K
a
1K
SLED MOTOR
I
(4) ib
(My)
0,015 p
™6
SC 22 yA
a irs oe
Oo
ike
I
SL@
+
c2y
82K
100K
=
(2)
TRACKING
FSET
C7)
510K
O0,01lp
motor depends on the current at TM5 or TM6 and the feed-
back resistance through pin 15, as shown
by the following
equation.
Sled jump peak voltage = TM5 (TM6) current x Feedback
resistance
The
currents
at these
switches
are
determined
by the
resistance connected
between
pins 29 and 31. When
the
value is 120 k-ohms, the currents are:
+11 pA at TM3 and TM4, and
+22 pA at TM5 and TM6.
The currents are inversely proportional to the resistance, and
the variable range is from about 5 to 40 pA with TMS.
S STOP is the signal used to detect the ON/OFF of the limit
switch
for detecting
the innermost
position for the linear
motor.
25
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