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1
2) Tracking servo system
A
The main equalizer of tracking servo is made up of digital
equalizer section. A block diagram of tracking servo is
showed in Fig 12.
B
a) Track jump
Track jump is performed automatically by the command of
the microcomputer according to the auto-sequence
function inside LSI. In this system, up to 100 tracks of
multi-jump is prepared for using as track jump at the
search time. In the test mode, 1, 4, 10, 32, 32 X 3 jump of
it and carriage move can be checked by mode selection.
For jumps up to 4 tracks, about half number of total jumps
(e.g., about 2 tracks are set for 4 tracks) are set by
C
microcomputer. The speed control (which counts the
length of TEC interval and controls TD so as to keep a
constant frequency) is conducted for any jump up to 5-100
tracks and a target number of total tracks is set by
microcomputer. The established number of tracks is
counted by using TEC signal.
From the moment when the set number is counted, brake
pulse is output for defined period of time, and a lens is
stopped. In this way, it is possible to close tracking and
continue normal play.
In addition, gain up of a tracking servo in the brake circuit
D
ON is performed for 50ms after stopping brake pulse in
order to increase lead-in of servo during track jump.
FF/REW operation in normal mode is carried out with
executing a single jump continuously. The speed is varied
according to place of destination and is about 10 or 20
times of normal mode.
E
F
8
1
2
IC201 UPD63763AGJ,UPD63761AGJ
F
129
TE
DIG.
A/D
E
AMP
EQ
130
CONTROL
JUMP
PARAMETERS
Fig.7 Tracking servo block diagram
2
3
TD
R214
R312
DAC
103
10K
8R2K
C215
1500pF
TD
t1
KICK
TEC
T. BRAKE
EQUALIZER
GAIN NORMAL
T. SERVO
Fig.8 Single track jump
t1
TEC
EQUALIZER
T.BRAKE
SERVO
Fig.9-1 Multi-track jump
CX-3168
3
4
IC302
BD7962FM
TO-
LENS
16
13
15
TO+
12
BRAKE
t2
ON
OFF
GAIN UP
NORMAL
OPEN
CLOSED
t2
GAIN UP
50ms
NORMAL
ON
OFF
OPEN
CLOSED
4
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