Pioneer YPM-MG2196ZF Service Manual page 55

6) Focus-error amplifier
The system outputs photodetector output (A+C) and
(B+D) as FE signal (A+C)-(B+D) from Pin 28 via the dif-
ference amplifier, then via the error amplifier.
Low-frequency components of voltage FEY is:
20kΩ
FEY=(A+C)-(B+D)X X
10kΩ
: (FE level of pickup unit x 5.02)
An S curve equivalent to approximately 1.6 Vp-p is
obtained at FE output (Pin 28) by using REFO as refer-
ence. The cut-off frequency of the amplifier of the last
layer is 12.4 kHz.
7) Tracking-error amplifier
Outputs E and F from the photodetector are output as
TE signal (E-F) from Pin 24 via the difference amplifier,
then via the error amplifier.
Low-frequency components of voltage TEY is:
63kΩ
TEY=(E-F) X X
(31kΩ+16kΩ)
: (TE level of pickup unit x 5.36)
TE waveforms equivalent to approximately 1.5 Vp-p are
obtained at TE output (Pin 24) by using REFO as refer-
ence. The cut-off frequency of the amplifier of the last
layer is 19.5 kHz.
8) Tracking zero-cross amplifier
Tracking zero-cross signal (TEC signal) is generated by
amplifying TE waveforms (voltage at Pin 24) by a factor
of four. The signal is used for detecting the zero-cross
point of tracking error in the servo LSI UPD63702AGF.
The purposes of detecting the zero-cross point are as
follows:
(1)To be used for counting tracks for carriage move and
track jump.
(2)To be used for detecting the direction of lens move-
ment when tracking is closed. (To be used in the
tracking brake circuit mentioned later.)
The frequency range of TEC signal is from 500 Hz to
19.5 kHz.
Voltage TEC = TE level x 4
In other words, the TEC signal level is calculated as 6
Vp-p. This level exceeds the D range of the operation
amplifier, resulting in the signal to clip. However,
there shall be no problem, since the servo LSI uses
only zero-cross point.
90kΩ R108
X
68.8kΩ 17.2kΩ
68kΩ
17kΩ
REFOUT (+2.5V)
gm CONDUCTANCE
20kΩ
A+C
10kΩ
6
10
10kΩ
11
20kΩ
B+D
13
13
10kΩ
CN101
12
FE VCA
10kΩ
gm=1/68.8kΩ
F.BAL
UPC2572GS
Fig. 4 Focus-error amplifier
REFOUT (+2.5V)
gm CONDUCTANCE
50pF
63kΩ
CN101
F
31kΩ
9 14
R117
16kΩ
50pF
63kΩ
E
31kΩ
11
15
R116
16kΩ
UPC2572GS
Fig. 5 Tracking-error amplifier,
Tracking zero-cross amplifier
YPM-MG2196ZF
6 5
C114
390pF
9.3kΩ
R108
9.3kΩ
33kΩ
27 28
50pF
90kΩ
17.2kΩ
38
REFOUT
R113
R114
C123
10kΩ
4.7nF 10kΩ
TBAL
R110
130kΩ
TOFST
37
R115
C115
1kΩ
120pF
C126
R109
15nF
68kΩ
25 24
5pF
TE VCA
gm=1/17kΩ
4R
R
TEC
23
C116
6.8nF
FE
TE
55