LG MCD112 User manual

MINI Hi-Fi SYSTEM
SERVICE MANUAL
MODEL : MCD112 (MCS112F)
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL .
Website http://biz.lgservice.com
MODEL: MCD112 (MCS112F)
SERVICE MANUAL
Internal Use Only
P/NO : AFN72956656 APRIL, 2009

1-1
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
CONTENTS
SECTION 1
GENERAL
SERVICING PRECAUTIONS ................................1-2
• NOTES REGARDING HANDLING
OF THE PICK-UP
• NOTES REGARDING COMPACT DISC
PLAYER REPAIRS
ESD PRECAUTIONS ............................................1-4
LOCATION OF USERS CONTROLS....................1-5
SPECIFICATIONS .................................................1-7
SECTION 2
EXPLODED VIEWS
CABINET EXPLODED VIEW................................2-1
TAPE DECK MECHANISM EXPLODED VIEW....2-3
1. TAPE DECK MECHANISM
(A/S & A/S : RIGHT A/S DECK) ..................2-3
2. TAPE DECK MECHANISM
(A/S & A/S : LEFT A/S DECK) ....................2-5
CD MECHANISM EXPLODED VIEW ...................2-7
SPEAKER EXPLODED VIEW ..............................2-9
MODEL : MCS112F.........................................2-9
PACKING ACCESSORY VIEW...........................2-13
SECTION 3
AUDIO PART ELECTRICAL
AUDIO ELECTRICAL
TROUBLESHOOTING GUIDE..............................3-1
1. POWER (SMPS) .........................................3-1
2. P-SENS .......................................................3-2
3. VKK CHECK................................................3-2
4. MICOM PART CHECK I ..............................3-2
5. MICOM PART CHECK II .............................3-3
6. IC103(KS4CD21CS) CHECK......................3-4
7. FLD DISPLAY CHECK ................................3-5
8. PWM MODULATION PART CHECK ...........3-6
9. POWER AMP PART CHECK ......................3-7
10. AUX FUNCTION CHECK ............................3-8
11. TUNER FUNCTION CHECK .......................3-9
12. TAPE FUNCTION CHECK ........................3-10
13. TAPE PLAY PART CHECK ........................3-11
14. TAPE REC PART CHECK .........................3-12
INTERNAL BLOCK DIAGRAM OF ICs..............3-13
1. ES6838.......................................................3-13
2. HA12237F. ..................................................3-14
3. PS9829B ....................................................3-15
4. PT6324 .......................................................3-15
5. STR-S6757IF1905......................................3-16
6. TAS5142 .....................................................3-17
7. U1739EJ2V1UD00/KF2_E .........................3-18
WIRING DIAGRAM .............................................3-19
BLOCK DIAGRAMS ...........................................3-21
1. SMPS BLOCK DIAGRAM .........................3-21
2. MAIN & FRONT BLOCK DIAGRAM .........3-23
SCHEMATIC DIAGRAMS ...................................3-25
1. SMPS SCHEMATIC DIAGRAM ................3-25
2. MAIN SCHEMATIC DIAGRAM..................3-27
3. AMP SCHEMATIC DIAGRAM ...................3-29
4. DECK SCHEMATIC DIAGRAM.................3-31
5. FRONT SCHEMATIC DIAGRAM .................3-33
6. KEY-L SCHEMATIC DIAGRAM ...................3-35
7. KEY-R SCHEMATIC DIAGRAM ...................3-36
PRINTED CIRCUIT BOARD DIAGRAMS...........3-37
1. MAIN P.C.BOARD .....................................3-37
2. FRONT P.C.BOARD..................................3-41
3. SMPS P.C.BOARD ....................................3-43
4. KEY-L P.C.BOARD ....................................3-44
5. KEY-R P.C.BOARD ...................................3-44
SECTION 4
CD PART ELECTRICAL
CD ELECTRICAL
TROUBLESHOOTING GUIDE..............................4-1
1. CD PART TROUBLESHOOTING................4-1
2. USB PART TROUBLESHOOTING..............4-9
WAVEFORMS OF MAJOR CHECK POINT .......4-10
SCHEMATIC DIAGRAMS ...................................4-13
1. CD SCHEMATIC DIAGRAM .....................4-13
2. USB SCHEMATIC DIAGRAM ...................4-15
PRINTED CIRCUIT BOARD DIAGRAM.............4-17
CD P.C.BOARD .............................................4-17
SECTION 5
REPLACEMENT
PARTS LIST............................................5-1

1-2
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
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 this.
6) Never attempt to disassemble the pick-up.
Spring by 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.
SERVICING PRECAUTIONS
SECTION 1 GENERAL

1-3
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
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 of humidity is high, where strong mag-
netism 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 (1MΩ)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent
static 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.
CLEARING MALFUNCTION
You can reset your unit to initial status if malfunction occur(button malfunction, display, etc.).
Using a pointed good conductor(such as driver), simply short the RESET jump wire on the inside of
the volume knob for more than 3 seconds.
If you reset your unit, you must reenter all its settings(stations, clock, timer)
NOTE: 1. To operate the RESET jump wire, pull the volume rotary knob and release it.
2. If you wish to operate the RESET jump wire, it is necessary to unplug the power cord.

1-4
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
ESD PRECAUTIONS
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 inte-
grated circuits and some field-effect transistors and semiconductor chip components. The following tech-
niques 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 know 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 ARROWHEAD SYMBOL. WITHIN AN EQUILATERAL
TRIANGLE, IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE
OF UNINSULATED "DANGEROUS VOLTAGE" THAT MAY BE OF SUFFICIENT MAGNI-
TUDE TO CONSTITUTE A RISK OF ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENED TO
ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY
INFORMATION IN SERVICE LITERATURE.

1-5
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
LOCATION OF USERS CONTROLS
FRONT PANEL
1
2
3
4
5
6
7
8
9
10
11
1. POWER
You can set up the unit into an economic power
save mode. In the power-on status, press and hold
(POWER) for about 3 seconds. To cancel
power save mode, press (POWER).
2. ST./MONO
Press ST./MONO. This will change the tuner from
stereo to mono and usually improve the reception.
3. MP3 OPT. (MP3 Optimizer)
This function is optimized for compressible MP3
files so that it improves the bass sound.
4. DEMO
Press DEMO in power off state to demonstrate the
function on display window. To cancel it, press
or DEMO again.
5. Headphone jack
Connect a headphone plug (ø3.5 mm) into the jack
to listen to the sound through headphones (not
supplied).
6. CD tray
7. XTS - PRO
The function creates the optimum sound for you to
play of the original sound. Each time you press
XTS - PRO, “XTS -- PRO ON” or “XTS -- PRO
OFF” is displayed in turn. (The XTS Pro function
will not be operated when a headphone has been
connected.)
8. D.SKIP
If more than one portable USB player is connected
to the system at the same time, press D.SKIP to
select one of them.
9. AUX
You can connect many other types of audio or
audio visual device to the system via the auxiliary
sockets (AUX IN) on the back of the player.
10.VOLUME
Control the volume when using any function.
11. USB connector - OPTIONAL
Connect a remote USB compatible player here.

1-6
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
REMOTE CONTROL
10
12
13
14
9
8
2
3
4
5
6
7
1
11
1. Search for a folder of MP3/WMA files
When a CD containing MP3/WMA files in several
folders is being played, press PRESET/FOLDER to
select the folder you want to play.
2. Fall asleep while listening to your player
Firstly, start a radio station or music. Press SLEEP
on the remote one or more times to select a delay
of between 10 and 180 minutes, after which the
player will turn off.
3. Use when playing a CD
4. Listen to your tracks again and again
Press REPEAT once to repeat the track currently
playing. Press REPEAT twice to repeat the whole
CD, or if you’re listening to the whole folder of
MP3/WMA CD . The display will show what is being
repeated.
5. Use when playing a cassette tape
6. Sound quality adjustment
You can select a desired sound mode by using EQ.
7. Play any track on a CD
Press the corresponding number buttons on the
remote control.
8. Temporarily stop the sound
Press the button again to return to the sound.
9. To change the functions
Change the functions between FM, AM, CD, AUX,
USB or TAPE
10.Dimm the display light
11. For storing radio stations
If you have saved radio stations using PROGRAM/
MEMO, you can scroll through them and select one
(see Listening to the radio).
12.eXtreme Dynamic Sound System
Reinforce the treble, bass and surround sound
effect. XDSS ON will show in the display. Press
again for XDSS OFF.
13.RANDOM
Press RANDOM, play tracks/files you can in a ran-
dom order or cancel it.
14.See information about your music
MP3/WMA files often come with tags. The tag gives
the Title, Artist or Album. Press INFO while a file is
playing to see this information. If there are no tags,
“NO ID3 TAG” or “NO WMA TAG” will show.

1-7
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
SPECIFICATIONS
• GENERAL
Net Weight 5.57kg (MCD212 Model)
5.36kg (MCD112 Model)
External dimensions (WxHxD) 170 x 243 x 282mm
• TUNER
FM Tuning Range 87.5 ~ 108.0MHz or 65 ~ 74MHz,
87.5 ~ 108.0MHz
AM Tuning Range 522 ~ 1620kHz or 520 ~ 1720kHz
• AMPLIFIER
Output Power 100W + 100W (MCD212 Model)
50W + 50W (MCD112 Model)
T.H.D 0.5%
Frequency Response 40 ~ 20000Hz
Signal-to-noise ratio 75dB
• CD
Frequency response 40 ~ 20000Hz
Signal-to-noise ratio 75dB
Dynamic range 75dB
• SPEAKERS
MCS212F Type Bass Reflex 2 Way 2 Speaker
Impedance 4Ω
Rated Input Power 100W
Max. Input Power 200W
Net Dimensions (WxHxD) 220 x 342 x 270mm
Net Weight (1EA) 3.46kg
MCS112F Type Bass Reflex 2 Way 2 Speaker
Impedance 4Ω
Rated Input Power 50W
Max. Input Power 100W
Net Dimensions (WxHxD) 200 x 337 x 228mm
Net Weight (1EA) 2.92kg

1-8
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
MEMO

2-1 2-2
SECTION 2 EXPLODED VIEWS
CABINET EXPLODED VIEW
255
256
E
F
G
I
J
H
A
B
B
M
N
A
J
K
H
L
L
K
M
I
C
G
E
F
D
A26
A41
A47
A46
266
263
305
451
267
289
456
450
264
458
450
450
450
290
290 454
CABLE2
CABLE4
CN806
P9701
P9702
260
CD
MAIN
SMPS
291
257
255
259
253
253
254
450
N
N
C
450
450
A00
CABLE1
CABLE5
CN201
CABLE3
A43
A40
FRONT
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only

2-3 2-4
TAPE DECK MECHANISM EXPLODED VIEW
1. TAPE DECK MECHANISM (A/S & A/S : RIGHT A/S DECK)
BRASS MOTOR PULLEY MAYBE CHANGED
FOR WOW FLUTTER WHEN NECESSARY
RING FW MAYBE ADDED
FOR WOW FLUTTER WHEN NECESSARY
001
002
006
007
008
016 017
018
019
020
003
A00
009
009
A02
A01
011
013
022
025
015
023
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only

2-5 2-6
2. TAPE DECK MECHANISM (A/S & A/S : LEFT A/S DECK)
RING FW MAYBE ADDED
FOR WOW FLUTTER WHEN NECESSARY
013
011
009
009
003
008
015
022
023
024
016 017
018
019
020
007
A03
A00
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only

2-7 2-8
CD MECHANISM EXPLODED VIEW
416
151
159
165
164
417
166
417
167
416
177
175
172
170
419
417
418 418
190
189
188
A30
A32
A26
181
187
186
184
421
421
185
156
155
153
173
168
163
162
441
440
422
A35
417
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only

2-9 2-10
SPEAKER EXPLODED VIEW
MODEL : MCS112F
850L
850R
853 855
854
852
851
A80B
A80L
A80R
A80AL
A80AR
856
WIRE80
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only

2-112-12
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
MEMOMEMO

2-13
Copyright©2009LGElectronics.Inc.Allrightreserved.
Only for training and service purposes
LGE Internal Use Only
PACKING ACCESSORY VIEW

2-14
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
MEMO

3-1
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
AUDIO ELECTRICAL TROUBLESHOOTING GUIDE
SECTION 3 AUDIO PART ELECTRICAL
1. POWER (SMPS)
POWER (SMPS)
OK
YES
YES
YES
Replace IC 901,902
Check IC901, 902
Check the fuse
F901
NONO
NO
YES
Check short of
P9701, P9702 line
Replace the fuse
Check
the DC V of C905.
If DC V is over
400V
NO Check BD901, LF901, 902
Check the
DC V of C981, C945.
If DC V is 6.1V
NO Check short of P9702 line
YES
YES
Chcek the
DC V of C950, C951
If DC V is in
31.5V
NO Check short of P9701 line
Chcek the
DC V of C909, C903,
C921 If DC V is in 14~19V
and it is steady.
YES

3-2
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
2. P-SENS
P-SENS
YES
YES
Check
the PIN6 of P9702
If DC V is over 5.6V
Check power circuit Trouble shooting
NO
OK
3. VKK CHECK
VKK check
YES
YES
Check
the PIN3 of P9702
If DC V is over -28V ±2 Check power circuit Trouble shooting
NO
OK
4. MICOM PART CHECK I
MICOM part check I
OK OK
YES
YES
Check P-SENS
(P7904)_PIN6.
NO Refer to
SMPS troubleshooting.
YES YES
YES
Check both
end voltage of IC101
(KIA7042).
Check
if input voltage of
IC101(KIA7042) is
over 5V.
YES
NO Check the
periphery of IC101
(KIA7042).
NO
YES
Check if IC101(KIA7042) of
output voltage is over 4.3V.
Check voltage of IC100
78KO/KF2_PIN1.
NO Replace IC101
(KIA7042).

3-3
Copyright © 2009LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
5. MICOM PART CHECK II
MICOM part check II
X101 : 32.768kHz
X100 : 9.8304MHz
Check the operation.
Check
Q101_ emitter/collector
5V.
Check Q102_base
0.6V HIGH.
Check if IC103_PIN8 and
IC100_PIN19, 20, 59 are 5V.
NO NO
YES
YES
Check if
voltage of P7904_PIN5
is 5.6V.
NO Refer to
SMPS troubleshooting.
YES
YES
YES
OK
YES
Check
both end voltage of
D101
YES
YES
Check D101.
NO Check if output of
D101(1SR35) is 5V.
YES
YES
YES
YES
Check IC101.
Q102_collector 0.6V LOW.
OK
Check if output of IC101
(KIA7042) is over 4.3V.
OK
NO Replace IC101.
NO Replace D101.
YES
Check Q102.
OK
NO Replace Q102.