Pioneer YPM-MG2196ZF Service Manual page 61

3) Carriage servo system
Output from low-frequency components (lens position
information) of the tracking equalizer is input to the car-
riage equalizer by the carriage servo. After obtaining a
certain gain, the system outputs drive signal from the
servo LSI. The signal is then applied to the carriage
motor via the driver IC. More specifically, the pickup
unit as a whole must be moved forward when lens off-
set during playback reaches a specified level. Therefore,
gain of equalizer is set so that voltage higher than the
activation voltage of the carriage motor is output. As
actual operation, a certain threshold level is set for
equalizer output in the servo LSI, and drive voltage is
output from the servo LSI only when the equalizer out-
put level exceeds that level. Thus, power consumption
is reduced. Depending on eccentricity, etc. of disc, the
equalizer output voltage may cross the threshold level
several times before the pickup unit as a whole starts
operation. At this time, waveforms of drive voltage
from LSI are output as pulse.
IC201 UPD63702AGF
FROM
DIGITAL
TRACK
EQUALIZER
EQUALIZER
CONTROL
KICK, BRAKE
REGISTERS
Fig. 15 Carriage Servo Circuit
TRACKING DRIVE
(LOW FREQUENCY)
LENS POSITION
DRIVE ON/OFF THRESHOLD
CRG DRIVE
(INSIDE UPD63702AGF)
CRG MOTOR VOLTAGE
Fig. 16 Carriage Signal Waveforms
YPM-MG2196ZF
IC301
BA5986FM
COP
SD
16
DAC 62 27
M
R305
15
D/A
26
10kΩ
COM
R306
25
7.5kΩ
DRIVER
CIN
CARRIAGE MOVED AT THESE POINTS
CARRIAGE
MOTOR
61