Samsung MAX-632P Service Manual page 4

5. Special Circuit Descriptions
5-1 CD
5-1-1 RF Amp (KA9220) : WIC01
58K
75
B
PD1
A C RF I-V AMP(1)
58K
PD2
D
74
Photo Detector
RF I-V AMP(2)
5-1-2 Focus Error Amp (KA9220) : WIC01
R2
174K
C1 25P
R1
V1 32K
-(B+D)
-(A+C)
32K
164K
C2 25P
63
FE Bias
Vcc
20K
5-1-3 Focus Servo System (KA9220) : WIC01
When FS3 is ON, high-frequency gain decreases (time constant is set by pin17, pin19, and capacitor connected to
internal resistance). The capacitor between pin18 and GND sets the time constant to pass low freqencies in PLAY
mode.
FE1
20K 58
0.0022
60
0.1UF
62
0.1UF
61
The maximum frequency of focus phase compensation is inversely proportional to the resistance connected to pin 7.
Focus search peak is about 1.1 Vp-p, and is inversely proportional to the resistance connected to pins 22,23
(if this resistance changes, the peak of track jump and sled kick change). The inversion input of FZC comparator is set
to 5.7% of the difference between Vcc and VC (pin69) {(5.7% x (Vcc-Vc)}.
Note : If the resistance connected to pin 7 changes, the phase compensation peak of focus,tracking,sled servos change.
At the same time, Ôop-ampÕ dynamic range and offset voltage also change.
Samsung Electronics
RF I-V Amp(I-1) and RF I-V Amp (I-2) are converted to voltage (via
internal resistance of 58k½) from the current of PD1 (A+C) and
PD2 (B+D):
RF SUMMING
R1
These voltages are added by the RF summing amplifier.
V1 AMP
10K
RFO
The signal (A+B+C+D) is applied to RFO (No.2 terminal)
66
RF output voltage is calculated as follows :
R3
10K
V
67
R2 V2
RF
FOCUS ERROR Amp AMPLIFIES the difference
between RF I-V Amp (1) output (A+C) and RF I-V Amp (2) output (B+D)
These two signals are supplied to (-) and (+) input terminals of the
FOCUS ERROR Amp. The FOCUS ERROR signal resulting from this
FE
difference voltage is applied to FE (Terminal No. 57).
57
FOCUS
The FE output voltage of this low frequency component varies according
ERROR
AMP
to {(A+C) - (B+D)}.
VFE is calculated as follows:
VFE=(R2/R1) X (V2-V1) = 5.4(V2-V1)
GND This FOCUS ERROR voltage is sent to FOCUS SERVO.
3.6K
60K
FZC
FE2
20K 48K
470K
FS4
DFCT
FDFCT
130K
HFGD
470K
46K
EFR
580K FS3
FSW
0.1UF
= -R3 x (iPD1 + iPD2)
RF
= -R3 x (V /R + V
1 1 2
V2
V1
= -R3 x ( +
10K
10K
R3
= x (V + V )
1 2
10K
92K
PHASE
COMPENSATION
40K
FS2
10K
40K
PFSET
27
6
/R )
2
)
FSEO
48
FOCUS
120K
COIL
47
FCE
5.5U 11U
ISET
50K
20
180K
21
FS1
VREG
FSCH
3
4.7UF
5-1