LG CM2520 User manual

Micro Hi-Fi System
SERVICE MANUAL
MODEL: CM2520 (CM2520, CMS2520)
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
MODEL: CM2520 (CM2520, CMS2520)SERVICE MANUAL
P/NO : AFN75734072 APRIL, 2012
Website http://biz.lgservice.com
Internal Use Only

CONTENTS
SECTION 1 ........ GENERAL
SECTION 2 ........ CABINET & MAIN CHASSIS
SECTION 3 ........ ELECTRICAL
SECTION 4 ........ REPLACEMENT PARTS LIST
1-1

SECTION 1
SUMMARY
CONTENTS
SERVICING PRECAUTIONS................................................................................................................... 1-3
ESD PRECAUTIONS.................................................................................................................................. 1-5
SERVICE INFORMATION FOR EEPROM .......................................................................................... 1-6
PROGRAM UPDATE GUIDE................................................................................................................... 1-7
SPECIFICATIONS ....................................................................................................................................... 1-8
1-2

NOTES REGARDING HANDLING OF THE PICK-UP
1. Notes for transport and storage
1) The pick-up should always be left in its conductive bag until immediately prior to use.
2) The pick-up should never be subjected to external pressure or impact.
2. Repair notes
1) The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.
2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and
impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or
damage to the printed-circuit board.
3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason
the adjustment point and installation screws should absolutely never be touched.
4) Laser beams may damage the eyes!
Absolutely never permit laser beams to enter the eyes!
Also NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.
5) Cleaning the lens surface
If there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as used
for camera lens). The lens is held by a delicate spring. When cleaning the lens surface, therefore, a cotton
swab should be used, taking care not to distort lens.
6) Never attempt to disassemble the pick-up.
Spring has excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab.
(Do not use any other liquid cleaners, because they will damage the lens.) Take care not to use too much
of this alcohol on the swab, and do not allow the alcohol to get inside the pick-up.
Storage in conductive bag Drop impact
NEVER look directly at the laser beam, and don’t allow
contact with fingers or other exposed skin.
Magnet
How to hold the pick-up
Conductive Sheet
Cotton swab
Pressure
Pressure
1-3
SERVICING PRECAUTIONS

NOTES REGARDING COMPACT DISC PLAYER REPAIRS
1. Preparations
1) Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). These components
are sensitive to, and easily affected by, static electricity. If such static electricity is high voltage, components
can be damaged, and for that reason components should be handled with care.
2) The pick-up is composed of many optical components and other high-precision components. Care must be
taken, therefore, to avoid repair or storage where the temperature or humidity is high, where strong magnet-
ism is present, or where there is excessive dust.
2. Notes for repair
1) Before replacing a component part, first disconnect the power supply lead wire from the unit
2) All equipment, measuring instruments and tools must be grounded.
3) The workbench should be covered with a conductive sheet and grounded.
When removing the laser pick-up from its conductive bag, do not place the pick-up on the bag. (This is
because there is the possibility of damage by static electricity.)
4) To prevent AC leakage, the metal part of the soldering iron should be grounded.
5) Workers should be grounded by an armband (1 MΩ)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent stat-
ic electricity changes in the clothing to escape from the armband.
7) The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.
Resistor
(1 MΩ)Conductive
Sheet
Resistor
(1 MΩ)
Armband
1-4

Electrostatically Sensitive Devices (ESD)
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components
commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated
circuits and some field-effect transistors and semiconductor chip components. The following techniques should
be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off
any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a
commercially available discharging wrist strap device, which should be removed for potential shock reasons
prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive surface
such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.
4. Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static" can
generate electrical charges sufficient to damage ESD devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESD
devices.
6. Do not remove a replacement ESD device from its protective package until immediately before you are
ready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together by
conductive foam, aluminum foil or comparable conductive materials).
7. Immediately before removing the protective material from the leads of a replacement ESD device, touch the
protective material to the chassis or circuit assembly into which the device will by installed.
CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL OTHER
SAFETY PRECAUTIONS.
8. Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless motion
such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate
static electricity sufficient to damage an ESD device).
CAUTION. GRAPHIC SYMBOLS
THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS
INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED
“DANGEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE A RISK OF
ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE
SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE
LITERATURE.
1-5
ESD PRECAUTIONS

POWER ON
FLD Display "NO DISC" status
Set Front ‘STOP’ Key +
Remote control ‘FWD SKIP’ Key
push same timing during 5s
FLD ‘OPT-XXXX’
Press SET Front "Play" Key Move to
appropriate position and make changes
with Set Front ‘FWD SKIP’ Key
Press Set Front ‘STOP’ Key +
Remote control ‘FWD SKIP’ Key
FLD Display ‘E2P CLR’
Press ‘POWER’ key
Completed
NAME
OPT
OPT
OPT
OPT
OPT
HEX
00000 (FM)
00001 (FM-NO IPOD)
01000 (FM_RDS)
10100 (FM_AM)
D1000 (FM_DAB)
DETECT NEW EEPROM
1-6
SERVICE INFORMATION FOR EEPROM

HOW TO UPDATE MCS PROGRAM
(1) Change the file name to download as “(MODEL NAME)__(function)_(Version).mcs”.
ex) CM2520_XXXX_XX.mcs
(2) Copy the file to the root folder of USB storage.
(3) Put the USB into the set. Change set function to USB function.
Then the upgrade process will be started with the upgrade intormation. FLD Display "UPGRADE".
(4) If the upgrade process is complete, the set will be rebooted with “SUCCESS” message
and set auto power off.
(5) Pull out the USB Storage. Press the power key.
1-7
PROGRAM UPDATE GUIDE

SPECIFICATIONS
1-8
•GENERAL
Power supply 100 - 240 V, 50 / 60 Hz or 200 - 240 V, 50 / 60Hz
Power consumption 35 W
Net Weight 2.3 kg
External dimensions (W x H x D) 230 x 125 x 243 mm
Operating conditions Temperature 5 °C to 35 °C (41 °F to 95 °F)
Operating humidity 5 % to 85 %
•TUNER
FM Tuning Range 87.5 to 108.0 MHz or 87.50 to 108.00 MHz
Amplifier
Output Power 30 W + 30 W
•CD
Frequency Response 40 Hz to 20 kHz
Signal-to-noise ratio 70 dB
Dynamic range 55 dB
•USB
USB Version USB 2.0 or USB 1.1
Bus Power Supply DC 5 V 500 mA
iPod/iPhone DC 5 V 1 A
•SPEAKERS
Type 2 Way 2 Speaker
Impedance 6 Ω
Rated Input Power 30 W
Max. Input Power 60 W
Net Dimensions (WxHxD) 150 x 251 x 158 mm
Net Weight(1EA) 1.56 kg
• Design and specifications are subject to change without notice.

SECTION 2
CABINET & MAIN CHASSIS
CONTENTS
EXPLODED VIEWS..................................................................................................................................... 2-3
1. CABINET AND MAIN FRAME SECTION (CM2520) ................................................................................ 2-3
2. PACKING ACCESSORY SECTION ......................................................................................................... 2-7
3. SPEAKER SECTION (CMS2520)............................................................................................................. 2-8
2-1

2-2
MEMO

EXPLODED VIEWS
1. CABINET AND MAIN FRAME SECTION (CM2520)
300
450
453
450
453
A26
A43
454
J
H
I
F
F
C
K
L
G
E
D
A
B
FRONT
USB
A48
251
259
258
A42
452
263
262
264
261
257
452
MAIN
CABLE11
CABLE10
CABLE12
453
270
J
H
453
453
G
B
K
A
I
C
D
SMPS
E
268
A47
A46
265
267
260
A49
451
256
269
451
255
IPOD
254
451
L
453
253
252
279
NOTES) THE EXCLAMATION POINT WITHIN AN
EQUILATERAL TRIANGLE IS INTENDED
TO ALERT THE SERVICE PERSONNEL
TO THE PRESENCE OF IMPORTANT
SAFETY INFORMATION IN SERVICE
LITERATURE.

MEMOMEMO

900 Remote Control
808 Battery
802 Box
803T Packing
803B Packing
804 Bag
801 Instruction Ass'y
2. PACKING ACCESSORY SECTION

A60L
A60R
3. SPEAKER SECTION (CMS2520)

SECTION 3
ELECTRICAL
CONTENTS
ELECTRICAL TROUBLESHOOTING GUIDE.................................................................................... 3-2
1. SMPS PART ........................................................................................................................................... 3-2
2. MUTE CIRCUIT ...................................................................................................................................... 3-4
3. AMP ABNORMAL................................................................................................................................... 3-5
4. FUNCTION MODE AUDIO ABNORMAL................................................................................................ 3-6
5. CD PART ................................................................................................................................................ 3-7
6. CD READING CHECK............................................................................................................................ 3-8
7. USB PART.............................................................................................................................................. 3-9
8. LCD DISPLAY CHECK......................................................................................................................... 3-10
9. IPOD PART .......................................................................................................................................... 3-11
WAVEFORMS............................................................................................................................................. 3-12
1. CD SEARCHING WAVEFORM............................................................................................................ 3-12
2. SPINDLE DRIVE & MOTOR WAVEFORM .......................................................................................... 3-12
3. CD PLAYING WAVEFORM.................................................................................................................. 3-13
4. CD STOP ACTION WAVEFORM......................................................................................................... 3-14
5. CD READING WAVEFORM................................................................................................................. 3-14
6. CD PLAYING RF WAVEFORM............................................................................................................ 3-15
7. USB OPERATING WAVEFORM.......................................................................................................... 3-16
8. RADIO OPERATING WAVEFORM...................................................................................................... 3-16
WIRING DIAGRAM ................................................................................................................................... 3-17
BLOCK DIAGRAM.................................................................................................................................... 3-19
CIRCUIT DIAGRAMS...............................................................................................................................3-21
1. SMPS CIRCUIT DIAGRAM .................................................................................................................. 3-21
2. MAIN - MCU CIRCUIT DIAGRAM........................................................................................................ 3-23
3. MAIN - DSP CIRCUIT DIAGRAM......................................................................................................... 3-25
4. MAIN - SERVO CIRCUIT DIAGRAM ................................................................................................... 3-27
5. MAIN - AMP CIRCUIT DIAGRAM ........................................................................................................ 3-29
6. MAIN - D/A CIRCUIT DIAGRAM.......................................................................................................... 3-31
7. MAIN - TUNER CIRCUIT DIAGRAM.................................................................................................... 3-33
8. DISPLAY CIRCUIT DIAGRAM ............................................................................................................. 3-35
9. IPOD CIRCUIT DIAGRAM.................................................................................................................... 3-37
CIRCUIT VOLTAGE CHART................................................................................................................. 3-39
PRINTED CIRCUIT BOARD DIAGRAMS ......................................................................................... 3-45
1. SMPS P.C.BOARD............................................................................................................................... 3-45
2. MAIN P.C.BOARD ................................................................................................................................ 3-47
3. DISPLAY P.C.BOARD.......................................................................................................................... 3-49
4. USB P.C.BOARD.................................................................................................................................. 3-49
5. IPOD P.C.BOARD ................................................................................................................................ 3-50
3-1

1. SMPS PART
+3.3 VA
Replace C912, IC907.
Replace BD901.
Replace IC902, PC901.
Replace F901 (Use same type fuse).
There is no power cord at the power jack.
Replace C953, C926, ZD904, R907, D902.
Replace FB904, T901.
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
C912, IC903
normal?
BD901
normal?
IC909, PC902
normal?
F901
normal?
Replace D905, C916, C917.
Replace RT901, LF901.
Is VCC (9.5V-26V) supplied to IC901 Pin2?
FB904, T901 normal?
NO
NO
NO
NO
YES
YES
D908, C910
normal?
RT901, LF901
normal?
Is VCC (130V-340V)
supplied to IC901 Pin5?
C925
130V-340V normal?
3-2
ELECTRICAL TROUBLESHOOTING GUIDE

+PVDD (20.5 V)
Replace C918, C916, C902, C905, C917.
Replace D913, D914.
YES
YES
YES
NO
NO
C918, C916, C902,
C905, C917 normal?
D913, D914
normal?
Replace IC908, PC901.
Replace ZD903, C923, Q907, D906, C909.
YES
YES
NO
IC908, PC901
normal?
Is VCC (130V-340V) supplied to IC901 Pin1?
Is VCC (9.5V-26V) supplied to IC901 Pin3? NO
3-3
ELECTRICAL TROUBLESHOOTING GUIDE

2. MUTE CIRCUIT
Mute abnormal
Check the speakers connection.
Replace IC107.
NO
YES
NO
NO
YES
YES
Check output signal
IC704 Pin31.
Check output signal
IC107 Pin90.
Replace FB314.
YES
Check input signal
of FB314.
Mute
3-4
ELECTRICAL TROUBLESHOOTING GUIDE

3. AMP ABNORMAL
AMP abnormal
Check the speakers connection.
Check the "PWM" of IC704 Pin27,28,29,30.
Check IC704 VCC of power circuit.
NO
NO
NO
YES
YES
YES
YES
Check output signal
L700 ~ L703.
Check the "High" PWR
of IC704 Pin31, 23, 32.
Check IC704
VCC(3.3 V) Pin21, 36.
Check IC704 VCC1 of power circuit.Check IC704 VCC1(18.6 V) Pin8, 11. YES
Replace L700 ~ L703,C777, C778.
NO
Check L700 ~ L703, C777, C778.
NO
YES
Check input signal of
IC704 Pin6, 9 ,10,13.
3-5
ELECTRICAL TROUBLESHOOTING GUIDE