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Service
Manual ORDER NO.
CRT2216
CD MECHANISM MODULE
CX-680
- This Service Manual outlines operations of the CD mechanism module used in the models listed
blow.
- For repair, use this Service Manual and the Service Manual of the model used in the system.
Model Service manual CD mechanism module CD mechanism unit
DEX-P1R/UC
DEH-P946/ES CRT2206 CXK5101 CXB1699
DEX-P1/ES
DEH-P945R/EW
CRT2207 CXK5101 CXB1699
DEX-P99R/EW
CONTENTS
1. CIRCUIT DESCRIPTIONS ........................................... 2
2. MECHANISM DESCRIPTIONS ................................. 15
3. DISASSEMBLY .......................................................... 17
CX-680
1. CIRCUIT DESCRIPTIONS
1.1 Preamplifier (UPC2572GS: IC101)
The preamplifier processes pickup output signals to EFM-IN 1 EFM comparator FE
38 FE-BAL
RF BAL
HPF
generate signals to be sent to the servo, demodula- envelope
AGC-OUT 2 AGC TE 37 TE-BAL
tor, and controller. The preamplifier with built-in BAL
C AGC 3 Detection 36 ASY
photodetector converts signals from the pickup into Vcc
X12
intermediate voltage in the pickup. Then, addition is RF-IN 4 35 EFM-OUT
made in the RF amplifier (IC101) to obtain RF, FE, TE, RF-OUT 5 34 C.DEF
Peak
and TE zero cross signals. The system consists of the DEFECT circuit
RF- 6 33 DEFECT
UPC2572GS and other components explained below. Bottom DC shift
C1.3T 7 32 RFOK
The system uses a single power source (+5 V). There-
fore, the reference voltage of IC101 and the reference C2.3T 8 Peak
Mirror circuit
31 MIRR
120k
voltage of the power unit and servo circuit are REFO Vcc 9 30 3T-OUT
Bottom
(+2.5 V). REFO is obtained from REFOUT of servo LSI A 10 DC shift 29 C.FE
(IC201: UPD63702GF) via a buffer, and is output from
C 11 3T detection Phase detection X3 28 FE-OUT
Pin 19 of IC101. This REFO is used as reference for all
B 12 FE BAL 27 FE-
measurements. Control
D 13 26 GND
Note: Do NOT short-circuit REFO and GND during
measurement. F 14 25 TE-
FE BAL
E 15 Control 24 TE-OUT1
PD 16 X2 23 TE-OUT2
Vcc
LD 17 22 DET-IN
APC
LDON 18 21 DET-OUT
VREF-OUT 19 20 VREF-IN
Fig. 1 Block Diagram of UPC2572GS
1) Automatic Power Control (APC) circuit
Pickup unit
Laser diode has negative temperature characteristics UPC2572GS
Vcc (5V)
with great optical output when the diode is driven 2.5V
with constant current. Therefore, current must be Vr
R112
16k
2.2k PD
controlled by a monitor diode to ensure constant out- 5 16
put. Thus functions the APC circuit. LD current can be LD MD
obtained by measuring the voltage between LD1 and
15 150k
C104 1k
GND. The current value is approximately 35 mA. Q101 1k
2SD1664 0.33