CONFIDENTIAL

SERVICE MANUAL
MINI HI-FI SYSTEM
SERVICE MANUAL

MODEL: CK57 (CK57, CKS57F/W)

MODEL: CK57
(CK57, CKS57F/W)

CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.

P/NO : AFN78432907 MARCH, 2017

“Any reproduction, duplication, distribution (including by way of email, facsimile or other

electronic means), publication, modification, copying or transmission of this Service Manual is
STRICTLY PROHIBITED unless you have obtained the prior written consent of the LG Electronics
entity from which you received this Service Manual. The material covered by this prohibition includes,
without limitation, any text, graphics or logos in this Service Manual.”

Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 CONTENTS

SECTION 1 ........ GENERAL

SECTION 2 ........ CABINET & MAIN CHASSIS
SECTION 3 ........ ELECTRICAL

1-1 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 SECTION 1
SUMMARY

CONTENTS

SERVICING PRECAUTIONS ............................................................................................................................ 1-3

ESD PRECAUTIONS ......................................................................................................................................... 1-5

HIDDEN KEY MODE ......................................................................................................................................... 1-6

1. HIDDEN KEY MODE TABLE
2. HIDDEN KEY MODE DESCRIPTION

PROGRAM DOWNLOAD GUIDE...................................................................................................................... 1-7

FOTA UPDATE STEP USING BT APP ............................................................................................................ 1-9

SPECIFICATIONS ........................................................................................................................................... 1-11

1-2 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 SERVICING PRECAUTIONS
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.

Storage in conductive bag Drop 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.

NEVER look directly at the laser beam, and don’t allow

contact with fingers or other exposed skin.

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 cot-
ton swab should be used, taking care not to distort lens.

Pressure
Magnet
Pressure

How to hold the pick-up

Cotton swab

Conductive Sheet

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.

1-3 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
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 magne-
tism 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 M)
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.

Armband

Resistor
(1 M)
Resistor
Conductive
(1 M)
Sheet

1-4 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 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 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 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 HIDDEN KEY MODE
1. HIDDEN KEY MODE TABLE
HIDDEN MODE ENTRANCE KEY(Audio) EXIT KEY
Front ‘Stop’ 
Version Check Remote Control Key ‘Play’ / for 1.5s
+ Remote Control Key ‘Play’ / for 5s
Front ‘Stop’ 
EEPROM INITIAL Auto exit
+ Remote Control Key ‘ ‘ for 5s

2. HIDDEN KEY MODE DESCRIPTION

2-1. Version Check
- Function : Version Check.
- Entrance Key : Front ‘Stop’ + Remote Control Key ‘Play’ for 5s.
- Exit Key : Remote Control Key ‘Play’ for 1.5s.
- Operation explanation : Remote Control Key OR .

2-2. EEPROM Initial

- Function : Initialize data stored in EEPROM and BACKUP RAM data.
- Entrance Key : Front ‘Stop’ + Remote Control Key ‘ ‘ for 5s.
- Exit Key : Auto exit.
- Explanation : ‘E2P CLR’ is displayed on the VPD and turn off the power automatically.

1-6 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 PROGRAM DOWNLOAD GUIDE
1. USB PROGRAM
Download program file name must be HG840_CK57_YYMMDDX.bin
If security program(Water Wall) is activated on PC, you must save the file to the USB storage device
and disable the security software, then download the file to your set.
Downloading file proceeds in the same way at USB1 function and USB2 function.

Caution: When downloading the file, you should neither unplug the USB device, change to the other function,
nor power off the device. USB device must be unplugged when the downloading process is completed.

ON VFD DISPLAY SCREEN

1) (Fast) Format USB device.

2) Copy Firmware file to USB device.

NO USB

 Insert USB device at USB function.

SEARCH


MCS


FINISH


AUTO POWER OFF

1-7 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
2. EQ & DEMO PROGRAM
Download program file name must be EQ_PRG.BIN
If security program(Water Wall) is activated on PC, you must save the file to the USB storage device
and disable the security software, then download the file to your set.
Downloading file proceeds in the same way at USB1 function and USB2 function.

Caution: When downloading the file, you should neither unplug the USB device, change to the other function,
nor power off the device. USB device must be unplugged when the downloading process is completed.

ON VFD DISPLAY SCREEN

1) (Fast) Format USB device.

2) Copy Firmware file to USB device.

NO USB

 Insert USB device at USB function.

SEARCH


EQDEMOUP


FINISH


AUTO POWER OFF

1-8 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 FOTA UPDATE STEP USING BT APP
Step1 : App connecting
Step2 : Device version info
(Check FW version)

After connecting the BT App with SET, When touch the “Device Version info” button,
the user could find the “Device Version info” on user could find the current and latest SET
Setting tab. version on pop-up menu.

Step3 : Select update button Step4 : Confirm update

When touch the “Update” button, user could Select the OK button on the caution message.
update the SET firmware using FOTA.

1-9 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 Step5 : Download from CDN server Step6 : Transfer FW

1st step is download from CDN server to After completed the download from server,
smart phone. The progress bar is displayed smart phone start to transfer the firmware to the
on BT App. SET. The progress bar is displayed on BT App.

Step7 : FW Flash Writing Step8 : FOTA complete

After completed the download from the smart When finishing the flash memory writing, pop-up
phone, the SET overwrite the firmware to flash message about finish is displayed and the SET
memory. auto power off.

1-10 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 SPECIFICATIONS
• GENERAL
Power requirements 120 V ~ 60 Hz
Power consumption 105 W
Dimensions (W x H x D) Approx. 350 mm x 166 mm x 276 mm
Operating temperature 5 °C to 35 °C
Operating humidity 60 %

• INPUTS
Analog audio in (AUX IN) 2.0 Vrms (1 kHz, 0 dB), 75 Ω, RCA jack (L, R)
Portable in (PORTABLE IN) 1.0 Vrms (3.5 mm stereo jack) x 1
Microphone (MIC) Sensitivity 20 mV (1 kHz), 6.3 mm jack x 1

• TUNER
FM Tuning Range 87.5 to 108.0 MHz or 87.50 to 108.00 MHz
AM Tuning Range 522 to 1,620 kHz, 520 to 1,710 kHz or 522 to 1,710 kHz

• SYSTEM
Frequency Response 40 to 20,000 Hz
Signal-to-noise ratio More than 75 dB
Dynamic range More than 75 dB
Bus Power Supply (USB) 5V 500 mA

• AMPLIFIER (RMS Output power)

Total output 1,100 W RMS
Front 350 W RMS X 2 (4 Ω at 1 kHz, 25 % THD)
Subwoofer 400 W RMS (3 Ω at 60 Hz, 25 % THD)

• FRONT SPEAKER
Type 2 Way 2 Speaker
Impedance 4Ω
Rated Input Power 350 W RMS
Max. Input power 700 W RMS
Dimensions (W x H x D) Approx. 300 mm x 363 mm x 256 mm

• SUBWOOFER SPEAKER
Type 1 Way 1 Speaker
Impedance 3Ω
Rated Input Power 400 W RMS
Max. Input power 800 W RMS
Dimensions (W x H x D) Approx. 310 mm x 363 mm x 256 mm

• Design and specifications are subject to change without notice.

1-11 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
1-12 Copyright © 2018 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
 SECTION 2
CABINET & MAIN CHASSIS

CONTENTS

EXPLODED VIEWS ........................................................................................................................................... 2-3

1. CABINET AND MAIN FRAME SECTION ................................................................................................. 2-3
2. PACKING ACCESSORY SECTION ......................................................................................................... 2-7
3. SPEAKER SECTION ................................................................................................................................ 2-8

DISASSEMBLY INSTRUCTIONS ................................................................................................................... 2-10

ASSEMBLY INSTRUCTIONS ......................................................................................................................... 2-19

2-1 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
2-2 Copyright © 2018 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
EXPLODED VIEWS
1. CABINET AND MAIN FRAME SECTION
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.

A
B
C

MAIN
D
E G
F

A46

SMPS 274
A47
H
BT
A52 D

CABLE1
266
A
B
273
C
E
MIC 254

A45 CABLE2 F

254 A00
272
A42
262

252 G
FRONT 272 263

A43

H 300

252

2-3 2-4 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
2-5 2-6 Copyright © 2018 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
2. PACKING ACCESSORY SECTION

825 FM antenna 900 Remote control

2-7 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
3. SPEAKER SECTION
3-1. FRONT SPEAKER

A60

2-8 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
3-2. SUBWOOFER SPEAKER

A90

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Only for training and service purposes.
 DISASSEMBLY INSTRUCTIONS
1. Case
1-1) Remove the 5 Screws.
1-2) Remove the Case.

Figure D1

2. Power Cord
2-1) Pull the Power Cord in the direction of Figure D2-1.

Figure D2-1

2-10 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
Power Cord
2-2) Open the two hooks, disconnect the harness cable from the SMPS PCB, and remove the power cord.

Figure D2-2

3. Plate Bridge
3-1) Pull the Front Assembly in the direction of  and remove the Plate Bridge in the direction of .

¢

¤

Figure D3

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Only for training and service purposes.
4. Front Assembly
4-1) Remove the 2 Screws.

Figure D4-1

4-2) Disconnect the 2 FFC Cables and the 2 Harness Cables from the MAIN PCB.

Figure D4-2

2-12 Copyright © 2018 LG Electronics Inc. All rights reserved.

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Front Assembly
4-3) Unhook the 2 Hooks ( in Figure D4-3) next to Front Assembly.

¢

Figure D4-3

4-4) Unhook the 2 Hooks ( in Figure D4-4) under the Front Assembly.
4-5) Remove the Front Assembly.

¤ ¤

Figure D4-4

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5. Knob
5-1) Remove the Knob by inserting a flat-head screwdriver in the position marked Figure D5.

Figure D5

6. FRONT PCB
6-1) Remove the 8 Screws from the FRONT PCB.
6-2) Remove the 2 Plate Grounds

Figure D6-1

2-14 Copyright © 2018 LG Electronics Inc. All rights reserved.

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FRONT PCB
6-3) Unhook the 2 Hooks from the FRONT PCB in the Figure 6-2.
6-4) Removing the FRONT PCB, be careful that the USB Connector does not fall apart.

Figure D6-2

7. JACK PCB
7-1) Unhook the 1 Hooks and Remove the JACK PCB.

Figure D7

2-15 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
8. BT Module
8-1) Unhook the 2 Hooks and Remove the BT Module.

Figure D8

9. Panel Rear
9-1) Remove the 5 Screws.
9-2) Remove the Panel Rear.

Figure D9

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10. MAIN PCB, SMPS PCB
10-1) Remove the 9 Screws.
10-2) Disconnect the 2 FFC Cables.
10-3) Remove the MAIN PCB and SMPS PCB.

Figure D10

11. Chassis
11-1) Remove the Chassis.

Figure D11

2-17 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
12. MD
12-1) Remove the 4 Screws.
12-2) Remove the MD.

Figure D12

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Only for training and service purposes.
 ASSEMBLY INSTRUCTIONS
1. MD
1-1) Assemble the MD.
1-2) Tighten the 4 Screws.

Figure A1

2. MAIN PCB, SMPS PCB

2-1) Assemble the Chassis.
c Be careful because the area around the bracket is sharp.

Figure A2-1

2-19 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
MAIN PCB, SMPS PCB
2-2) Assemble the MAIN PCB & SMPS PCB.
2-3) Connect the 2 FFC Cables.
2-4) Tighten the 10 Screws.

Figure A2-2

3. Panel Rear
3-1) Assemble the Panel Rear.
c Be careful because the area around the Panel Rear is sharp.
3-2) Tighten the 5 Screws.

Figure A3

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Only for training and service purposes.
4. BT Module
4-1) Assemble the BT Module.

Figure A4

5. JACK PCB
5-1) Assemble the JACK PCB.

Figure A5

2-21 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
6. FRONT PCB
6-1) Assemble the front PCB to match the marked hook.

Figure A6-1

6-2) Assemble the Plate Ground.

6-3) Tighten the 8 Screws.

Figure A6-2

2-22 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
7. Knob
7-1) Assemble the Knob.

Figure A7

8. Front Assembly
8-1) Assemble the Front Assembly to the marked hook.

Figure A8-1

2-23 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
Front Assembly
8-2) Connect the 2 FFC Cables and the 2 Harness Cables from the MAIN PCB.

Figure A8-2

8-3) Tighten the 2 Screws.

Figure A8-3

2-24 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
9. Plate Bridge
9-1) Assemble the Plate Bridge.

Figure A9

10. Power Cord

10-1) Insert the Power Cord into the hook as shown in Figure D10-1.

Figure A10-1

2-25 Copyright © 2018 LG Electronics Inc. All rights reserved.

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Power Cord
10-2) Insert the Power Cord into the Panel Rear as shown in Figure D10-2.

Figure A10-2

11. Case
11-1) Assemble the Case.
11-2) Tighten the 5 Screws.

Figure A11

2-26 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 SECTION 3
ELECTRICAL

CONTENTS

ONE POINT REPAIR GUIDE ............................................................................................................................3-2

1. NO POWER ............................................................................................................................................3-2
2. NO BOOTING WHEN POWER ON THE SET........................................................................................3-4
3. VFD IS NOT DISPLAYED WHEN POWER ON THE SET .....................................................................3-5
4. NO OPERATION OF MD ........................................................................................................................3-6
5. NO SOUND ...........................................................................................................................................3-11

ELECTRICAL TROUBLESHOOTING GUIDE.................................................................................................3-16

1. POWER (SMPS) ...................................................................................................................................3-16
2. MCS PART CHECK ..............................................................................................................................3-19
3. IC503 CHECK .......................................................................................................................................3-19
4. FLD DISPLAY CHECK .........................................................................................................................3-20
5. PWM MODULATION CHECK ...............................................................................................................3-21
6. POWER AMP PART CHECK ...............................................................................................................3-22
7. AUX / TUNER FUNCTION CHECK ......................................................................................................3-23
8. TUNER FUNCTION CHECK.................................................................................................................3-23
9. CD FUNCTION .....................................................................................................................................3-24
10. DOUBLE USB FUNCTION ...................................................................................................................3-25

WAVEFORMS OF MAJOR CHECK POINT....................................................................................................3-26

WIRING DIAGRAM ..........................................................................................................................................3-27

BLOCK DIAGRAMS ........................................................................................................................................3-29

1. SYSTEM BLOCK DIAGRAM ................................................................................................................3-29
2. POWER BLOCK DIAGRAM .................................................................................................................3-31

CIRCUIT VOLTAGE CHART ...........................................................................................................................3-33

1. CONNECTORS .....................................................................................................................................3-33
2. CAPACITORS .......................................................................................................................................3-33
3. ICs .........................................................................................................................................................3-34

PRINTED CIRCUIT BOARD DIAGRAMS .......................................................................................................3-35

1. SMPS P.C.BOARD ...............................................................................................................................3-35
2. MAIN P.C.BOARD ................................................................................................................................3-37
3. FRONT P.C.BOARD .............................................................................................................................3-39
4. MIC P.C.BOARD DIAGRAM .................................................................................................................3-41

3-1 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
1. NO POWER
If the unit doesn’t work by no power problem, repair the set according to the following guide.

1-1. FUSE & BRIDGE DIODE

1-1-1. Solution
Please check and replace F901, BD901, TH901 or TH903 on SMPS board.

1-1-2. How to troubleshoot (Countermeasure)

1) Check if the fuse F901 is open or short-circuit.
2) Check if the bridge diode BD901 is short-circuit by over current with a digital multi meter.
3) Check if the NTC thermistor TH901 or TH903 is normal or open.

1-1-3. Service hint (Any picture / Remark)

< F901 >

< BD901 > < TH901 >
If F901 is not short-circuit,
If BD901 is short-circuit, If TH901 is open,
replace it with a same specifica-
replace it with a new one. replace it with a new one.
tions one.

3-2 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO POWER
If the unit doesn’t work by no power problem, repair the set according to the following guide.

1-2. D921, D922

1-2-1. Solution
Please check and replace D921, D922 on SMPS board.

1-2-2. How to troubleshoot (Countermeasure)

1) Check the anode-cathod voltage of D921, D922 with a digital multi-meter, it is normally 0.2 ~ 0.3 V.
 If it doesn’t have any voltage, it’s destroyed. Replace it with a new one.

1-2-3. Service hint (Any picture / Remark)

< SMPS schematic diagram >

3-3 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
2. NO BOOTING WHEN POWER ON THE SET
The set doesn’t work when press the power button on the front board or the remote control.

2-1. FLASH MEMORY

2-1-1. Solution
Please check and replace IC501 on MAIN board.

2-1-2. How to troubleshoot (Countermeasure)

1) Check 12VA to IC102 in standby mode.
 If there is no 12 VA, check the SMPS.
2) Check 12VA and PVDD when power on the set.
- If the set doesn’t work regardless of what the KEY2 changes high to low while pressing the power button.
X500 and X501 work normally but, if you can not power on the set, replace IC500 with a new one on
the MAIN board.

2-1-3. Service hint (Any picture / Remark)

KEY2

IC500
X500

X501
IC501

12 VA

IC102

< MAIN board top view >

3-4 Copyright © 2018 LG Electronics Inc. All rights reserved.

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 ONE POINT REPAIR GUIDE
3. VFD IS NOT DISPLAYED WHEN POWER ON THE SET
When power on the set, any icons or characters on VFD are not displayed.

3-1. VFD
3-1-1. Solution
Please check and replace VFD301 on FRONT board.

3-1-2. How to troubleshoot (Countermeasure)

1) Check if 12 VA is output from SMPS to VFD via the MAIN board.
2) Check if Check if VFD_5 V, DVCC_3 V to CN304 is normal.
3) Check if IC500 outputs VFD_DAT, VFD_CLK and VFD_STB to the FRONT board.
4) Check if VFD301 output SW signal to the FRONT board.
 If the SW signal isn’t output, replace VFD301 with new one.
5) check if Q300 and Q301 to the FRONT board.
 If the VH signal isn’t output, replace Q301, Q302 with new one.
 If the VH signal is output, replace VFD301 with new one.

3-1-3. Service hint (Any picture / Remark)

< Waveform of GR and SG signal >

3-5 Copyright © 2018 LG Electronics Inc. All rights reserved.

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 ONE POINT REPAIR GUIDE
4. NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD disc if
the servo motors in MD don’t work. This step is for checking the SPINDLE MOTOR among them.

4-1. SPINDLE MOTOR

4-1-1. Solution
Please check and replace IC400, IC401 on MAIN board.

4-1-2. How to troubleshoot (Countermeasure)

1) Check the SPDO signal from pin16 of IC401.
 If no signal, check 3.3 V(RF) and X400.
2) Check the SPIN- & SPIN+ from IC400 to CN401 for driving SPINDLE motor. It is about 3.6 Vp-p.
 If no signal, check VDD_CORE and DVCC_3.3V for IC401.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the spindle motor is sort-circuit or has any trouble, it can not rotate CD discs.
Please check the function after changing another MD.

4-1-3. Service hint (Any picture / Remark)

SP- : pin18 to CN401(pin8)

SP+ : pin17
to CN401(pin6)
About 3.6 Vpp
IC400
CN401

< Waveform of SP- & SP+ < MAIN

board top < MAIN board bottom view >
for driving SPINDLE motor > view >

3-6 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD disc if
the servo motors in MD don’t work. This step is for checking the SLED MOTOR among them.

4-2. SLED MOTOR

4-2-1. Solution
Please check and replace IC400, IC401 on MAIN board.

4-2-2. How to troubleshoot (Countermeasure)

1) Check the SLDO signal from Pin15 of IC401.
 If no signal, check DVCC_3.3V and X400.
2) Check the SLED+ & SLED- from IC400 to CN401 for driving SPINDLE motor. It is about 2.9 Vp-p.
 If no signal, check VDD_CORE and DVCC_3.3V for IC401.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the sled motor is sort-circuit or has any trouble, it can not move the pickup module.
Please check the function after changing another MD.

4-2-3. Service hint (Any picture / Remark)

IC400
SLED- : pin18
SL- TO CN401
CN401

to CN401(pin9)
SL+ TO CN401

SLED+ : pin17
to CN401(pin7)
< Waveform of SLED- & SLED+ < MAIN
board top < MAIN board bottom view >
for driving SLED motor > view >

3-7 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD disc if
the servo motors in MD don’t work. This step is for checking the TRAY OPEN / CLOSE MOTOR among
them.

4-3. TRAY OPEN / CLOSE MOTOR

4-3-1. Solution
Please check and replace IC400, IC401 on MAIN board.

4-3-2. How to troubleshoot (Countermeasure)

1) Check MOT_OPEN & MOT_CLOSE signals from Pin P4, L4 of IC500 to IC400.
 If no signal, check VDD_CORE and DVCC_3.3V to IC401.
2) Check LOAD± from IC400 to CN401 for driving the tray open / close motor. It is about 3.85 Vp-p.
 If no signal, check M_5V to IC400. If it has any trouble, replace it with a new one.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the tray motor is sort-circuit or has any trouble, it can not open or close the tray.
Please check the function after changing another MD.

4-3-3. Service hint (Any picture / Remark)

MOT_CLOSE : pin6 to IC500

MOT_OPEN : pin7 to CN401

IC400
MOT_OPEN
CN401

CLOSE
LO- TO CN401
LO+ TO CN401 LOAD+ : pin9 to CN401(pin4)
LOAD- : pin10 to CN401(pin2)

< Waveform for driving < MAIN

board top < MAIN board bottom view >
TRAY open / close motor > view >

3-8 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD disc if
the pickup module in MD doesn’t work. This step is for checking the LASER TRACKING ACTUATOR.

4-4. LASER TRACKING ACTUATOR

4-4-1. Solution
Please check and replace IC400, IC401 on MAIN board.

4-4-2. How to troubleshoot (Countermeasure)

The tracking actuator makes the laser beam be positioned in the center of a track on CD disc.
1) Check the TRD signal from Pin14 of IC401.
 If no signal, check DVCC_3.3V and X400.
2) Check TR- & TR+ from IC400 to CN400 for driving the tracking actuator.
 If no signal, check M_5V and +5 V for IC400.
3) Check if the FFC cable is solidly connected between CN400 and MD.
4) Check the MD.
 If the pickup module has any trouble, it can not move the laser beam on the left or right side.
Please check the function after changing another MD.

4-4-3. Service hint (Any picture / Remark)

TR+ : pin16 to CN400(pin16)

CN400

TR- : pin15 to CN401(pin17)

IC400

< Waveform of TR± < MAIN

board top < MAIN board bottom view >
for driving TRACKING actuator > view >

3-9 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD disc if
the pickup module in MD doesn’t work. This step is for checking the LASER FOCUSING ACTUATOR.

4-5. LASER FOCUSING ACTUATOR

4-5-1. Solution
Please check and replace IC400, IC401 on MAIN board.

4-5-2. How to troubleshoot (Countermeasure)

The focusing actuator makes the laser beam keep a regular interval with the surface of a CD disc.
1) Check the FDO signal from Pin13 of IC401.
 If no signal, check DVCC_3.3V and X400.
2) Check F- & F+ from IC400 to CN400 for driving the focusing actuator.
 If no signal, check M_5V for IC401.
3) Check if the FFC cable is solidly connected between CN400 and MD.
4) Check the MD.
 If the pickup module has any trouble, it can not move the laser beam on the top or bottom side.
Please check the function after changing another MD.

4-5-3. Service hint (Any picture / Remark)

CN400

IC400

F- : pin13 to CN401(pin18)
F+ : pin14 to CN400 (pin15)

< Waveform of F± < MAIN

board top < MAIN board bottom view >
for driving FOCUSING actuator > view >

3-10 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
5. NO SOUND
There is no sound output in the CD FUNCTION, repair the set according to the following guide.

5-1. IN THE CD FUNCTION

5-1-1. Solution
Please check and replace IC500, IC400, IC401 and IC701, IC702 on MAIN board.

5-1-2. How to troubleshoot (Countermeasure)

1) Check CD_BCK, CD_LRCK, & CD_DATA signals from IC401 to IC500.
 If no signal, check if the RF & servo signals from MD is entered to IC401.
Refer to the “No operation of MD” guide on Item 4.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- MCS_BCK : IC500_Pin E1 --> IC700_Pin23
- MCS_LRCK : IC500_Pin D1 --> IC700_Pin22 (44.1 kHz)
- MIX_DATA0_OUT : IC500_Pin E2 --> IC700_Pin24
 If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to
the IC is distorted or no signal, replace it with a new one.
3) Check if “Digital audio AMP block” on Item 5-2 is normal.

5-1-3. Service hint (Any picture / Remark)

CD_RST
( VCC50) A, B, C, D, E, F, PD SERVO
LD
I C401
P/ UP ( 4 X)
SPDO/ SLDO CD_RW/ MCLK/ LRCK/ BCK,
/ FOD/ TRD CD_DAT

I C400 MOT_MUTE, CLOSE, OPEN

M LOAD± , SLED± , Mot or Dr i ve
SPI N± , TR± , F±

DECK
OP_SW, CL_SW, UP_SW, DN_SW, D_SENSE
MECHANI SM

( +3. 3V_CD, VCC1. 2)

MD
Bl ock I C501
Mai n DSP

MCS_MCLK (16.93 MHz)

MCS_BCK(1.4 MHz)
PWM_LRCK/ BCK/ DATA

LPF MCS_DATA_OUT
FRONT( BTL)

PWM AMP MCS_LRCK(44.1 KHz)

I C700 I C702 FRONT( BTL)

CK57 Only
LPF SW(PBTL)
AMP
I c701

PWM + AMP Bl ock

[CK57 : Total 2.1ch 1100W
350+350+400]
[CK56 : Total 2ch 700W]

< I2S Signal Flow > < Waveform of I2S audio interface signals >

3-11 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO SOUND
There is no sound output by DIGITAL AUDIO AMP DAMAGE, repair the set according to the following
guide.

5-2. BY DIGITAL AUDIO AMP DAMAGE (IN ALL FUNCTIONS)

5-2-1. Solution
Please check and replace IC701, IC702 on MAIN board.

5-2-2. How to troubleshoot (Countermeasure)

1) Check PWM_FL±, PWM_FR± & PWM_SW± signals from IC700 to IC701, IC702 each input function.
 If no signal, check if I2S audio signals are entered to IC700.
Refer to “I2S audio signal interface” on Item 5-1.
2) Check PVDD.
 If PVDD is abnormal, check the SMPS.
3) Check +12 V for driving the gate of AMP IC.
a. All the powers are normal, but if +12 V is low, there is possible for AMP IC to be damaged.
b. Remove L702, L703(FRONT), L701 and L704(WOOFER) one by one.
When removed a inductance, if +12 V is recovered, the IC connected to it was damaged.
c. Replace the IC with a new one.
4) Check the impedance between IC701/IC702_OUT_A/OUT_B/OUT_C/OUT_D & GND.
a. If the impedance is 0 Ω, the IC must be damaged.
b. After removing the heat sink, replace it with a new one.

5-2-3. Service hint (Any picture / Remark)

OUT_B OUT_C OUT_B OUT_C

OUT_A
OUT_A OUT_D
OUT_D
IC702 IC701

L703 L702 L704 L701

< MAIN board top view >

3-12 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO SOUND
There is no sound output in the USB FUNCTION, repair the set according to the following guide.

5-3. IN THE USB FUNCTION

5-3-1. Solution
Please check and replace IC500 and IC104 on MAIN board.

5-3-2. How to troubleshoot (Countermeasure)

1) Check +USB_5V to Front USB board.
2) Check USB D1± or USB D2± from MAIN board to Front USB board.
a. Check 2.0_D1±signals(pin U7, U8 ) or 1.1_D1± signals(pin A7, A8 ) to IC500.
b. Check USB± signals to CN502(pin1, 2, 4, 5).
3) If there is any trouble, check the power for each IC. The power is normal but , if the signal waveform to
the IC is distorted or no signal, replace it with a new one.

5-3-3. Service hint (Any picture / Remark)

2. 0 1. 1
CD_RST USB1 USB2
( VCC50) A, B, C, D, E, F, PD SERVO
LD
I C401
P/ UP ( 4 X)
SPDO/ SLDO CD_RW/ MCLK/ LRCK/ BCK,
/ FOD/ TRD CD_DAT

MOT_MUTE, CLOSE, OPEN D1+/ -

I C400
M LOAD± , SLED± , Mot or Dr i ve D2S+/ -
SPI N± , TR± , F±

DECK
OP_SW, CL_SW, UP_SW, DN_SW, D_SENSE
MECHANI SM

( +3. 3V_CD, VCC1. 2)

MD
Bl ock I C501
Mai n DSP
PWM_LRCK/ BCK/ DATA

LPF
FRONT( BTL)

PWM AMP
I C700 I C702 FRONT( BTL)

CK57 Only
LPF SW(PBTL)
D- to pin 1&4 of CN502
AMP
I c701

D+ to pin 2&5 of CN502

PWM + AMP Bl ock
[CK57 : Total 2.1ch 1100W
350+350+400]
[CK56 : Total 2ch 700W]

< USB function signal flow > < Waveform of USB D± signal >

3-13 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO SOUND
There is no sound output in the AUX FUNCTION, repair the set according to the following guide.

5-4. IN THE AUX FUNCTION

5-4-1. Solution
Please check and replace IC202 on MAIN board.

5-4-2. How to troubleshoot (Countermeasure)

1) Check AUX_L/R signals to IC202 (Pin27, 28).
2) Check if MCS_BCK, MCS_LRCK & MCS_MCLK are entered from IC500 to IC202.
3) Check if ADC_DATA is entered from IC202 to IC500.
 If no signal, check AVCC_3.3V & DVCC_3.3V for IC202. If is NG, replace it a new one.
4) Check the following I2S signal flow from IC500 to IC700.
 If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to
the IC is distorted or no signal, replace it with a new one.

5-4-3. Service hint (Any picture / Remark)

AUX I N

( +3. 3V_CD, VCC1. 2)

I C501 I C202
Mai n DSP

IC202
AUX_R/ AUX_L
PWM_LRCK/ BCK/ DATA

LPF
FRONT( BTL)

ADC_D/ ATA_IN
PWM AMP
I C700 I C702 FRONT( BTL)

CK57 Only
LPF SW(PBTL)
BCK LRCK
AMP
I c701

PWM + AMP Bl ock

[CK57 : Total 2.1ch 1100W
350+350+400]
[CK56 : Total 2ch 700W]

< AUX function signal flow > < MAIN board top view >

3-14 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ONE POINT REPAIR GUIDE
NO SOUND
There is no sound output in the TUNER FUNCTION, repair the set according to the following guide.

5-5. IN THE TUNER FUNCTION

5-5-1. Solution
Please check and replace IC202 and IC200 on MAIN board.

5-5-2. How to troubleshoot (Countermeasure)

1) Check if TUNER_LR is entered from pin14. 13 of IC 200 to IC202(Pin29, 30).
 If no signals, check AVCC_3.3V for IC200 power.
 Check if the tuner control signals (CLK, DAT, CE, RST, SLT) are entered from IC500 to IC200.
If it doesn’t work, replace IC200 with a new one.
2) Check if MCS_BCK, MCS_LRCK, & MCS_MCLK are entered from IC500 to IC202.
3) Check if ADC_DATA_IN is entered from IC202 to IC500.
 If no signal, check AVCC_3.3V & DVCC_3.3V for IC202. If is NG, replace it with a new one.
4) Check the following I2S audio signal flow from IC500 to IC700.
 If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to
the IC is distorted or no signal, replace it with a new one.

5-5-3. Service hint (Any picture / Remark)

( +3. 3V_CD, VCC1. 2)

I C501 I C202
Mai n DSP FM/AM TUNER
( FM/ AM)
IC202
TUNER_R/ TUNER_L
PWM_LRCK/ BCK/ DATA

LPF
FRONT( BTL)

PWM
I C700
AMP
I C702 FRONT( BTL)
ADC_D/ ATA_IN
CK57 Only BCK LRCK
LPF SW(PBTL)
AMP
I c701

PWM + AMP Bl ock

[CK57 : Total 2.1ch 1100W
350+350+400]
[CK56 : Total 2ch 700W]

< MAIN board top view >

< TUNER IN function signal flow >

3-15 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
1. POWER (SMPS)

No 5.6 VA

YES
NO
F901 normal? Replace F901 (Use the same fuse).

YES
NO
BD901 normal? Replace BD901.

YES
NO
TH901(TH903) normal? Replace TH901.

YES

Is Vcc
NO
(10 V ~ 18 V) supplied to D902 normal?
IC901 pin7?

NO

YES Check or replace D902.

NO
D933 / D934 normal? Replace D933 / D934.

YES

Is there NO
about 2.5 V at Replace IC941.
IC941 pin1?

YES
NO
D935 normal? Replace D935.

YES
NO
D932 normal? Replace D932.

YES
NO
D931 normal? Replace D931.

YES

Power line of main PCB is short.

3-16 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
POWER (SMPS)

No PVDD

YES
NO
F901 normal? Replace F901 (Use the same fuse).

YES
NO
BD901 normal? Replace BD901.

YES
NO
TH901(TH903) normal? Replace TH901.

YES
Is Vcc NO
(10 V ~ 18 V) supplied to NO
D903 normal?
IC911 Pin4?
YES

YES Check or replace D903.

NO
Q911 base HIGH?

YES

• Check P_CTRL HIGH signal from MCS.

• Check PC902.

Check or replace Q911.

NO
Q901 normal? Replace Q901.

YES
NO
D951 normal? Replace D951.

YES

Is there about 2.5 V NO

Replace IC951.
at IC951 pin1?

YES

Power line of main PCB is short.

3-17 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
POWER (SMPS)

No 12 V

YES

Is Vcc (15 V) NO
Check or replace D935.
supplied to IC931?

YES

NO
IC931 Pin4 “H”? Check P-CTRL “H” signal from MCS.

YES

Check or replace IC931.

No VFD

YES

NO
D931 normal? Check or replace D931.

YES

NO
ZD931 normal? Check or replace ZD931.

YES

NO
Q301 / Q302 normal? Check or replace Q301 / Q302.

YES

Check or replace VFD.

3-18 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
2. MCS PART CHECK

MCS PART CHECK

YES

Check if voltage of CN102 NO

Refer to SMPS troubleshooting.
Pin13, 14 is 12 VA..

YES

Check if IC100 NO
Check and change IC100.
have 3.3 VA output.

YES

Check if IC101 NO
Check and change IC101.
have 1.2 VA output.

YES

X500: 24 MHz, X501: 32.768 kHz

Check the operation.

YES

OK

3. IC503 CHECK

CHECK IC500 PIN.

YES

Check NO Check MCS NO

pinA12, pinB12 SF_SCK : Refer to MCS troubleshooting.
voltage 3.3 VA.
SF_MISO
YES
YES

NO
Check IC500. Replace IC500.

YES

OK OK

3-19 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
4. FLD DISPLAY CHECK

FLD DISPLAY CHECK

YES

Check NO
CN102 Pin13,14 input Refer to SMPS troubleshooting.
12V voltage.

YES

Check if both end voltage of F+, F- are over 1.85 V

VH : over 27 V.

YES

Check NO
CN300 connection and NO
power Pin14, 16, 17 Check CN304 connection. Check each Pin voltage.
(VIN, F+, VDD).

YES
YES

Check
VFD301 voltage Pin27, NO If voltage isn’t over VH : 27 V, F- : 3 V
26, 31, 32 VH: over 27 SW signal is not operation? OK
V, SW Signal, F- : over
3 V is OK?
YES
YES
NO
Check VFD301. Replace VFD301.

YES

OK

Check
IC500->VFD301 data NO Check input data
communication STB/ IC500 Pin F2, B3, B1.
DATA/ CLK
YES
YES

Check output data IC500 Pin B3.

YES

NO
FLD light on? Check IC500. Replace IC500.

YES
YES

OK OK

3-20 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
5. PWM MODULATION CHECK
PWM MODULATION PART
CHECK

YES

Check CN102 NO Refer to

Pin13, 14 (12 VA). SMPS troubleshooting.

YES

• Check IC700(TAS5548) VDD 3.3 V - Pin9,14.35,50.

• Check X700 (12.288 MHz).

YES

Check NO NO
X700(12.288 MHz) Check X700 Replace X700(12.288 MHz).
operation. (12.288 MHz).

YES YES

Check IC700 Pin21 CLK input. OK

YES

Check Check
NO CD Assy communication NO
IC700 input data Pin24, 25 Refer to CD troubleshooting.
Pin20,21, 22, 23,
PWM wave. 24.

YES YES

Check NO
IC700 input Check each line resistor output.
data.

YES

OK

Check PWM
modulator output NO NO
FL: Pin48(-),49(+)/ FR: Pin46(-),47(+). Check IC700. Replace IC700.
WF : 44(-), 45(+) Other output
check.

YES YES

OK OK

3-21 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
6. POWER AMP PART CHECK

POWER AMP PART CHECK

YES

Check NO
Refer to SMPS troubleshooting.
CN102 Pin13, 14: +12 VA
Check IC106 for +12 V.
Pin5, 6, 7 : 49 V.

YES

Check IC701, IC702

Pin25, 26, 38 , 39, 42, 43, 50, 51, 55, 56, 64
input voltage.

YES

NO
Check IC701, IC702
Check each line resistor output voltage.
Pin64: +12 V input.

YES

Check PWM Modulator input

IC701 Pin4, 5 / IC702 Pin4, 5. 10, 11.

YES

Check PWM modulator output

IC701/IC702 : pin28, 29, 36, 37, 44, 45, 52, 53.

YES

NO
Check output
Replace the coil.
line coil (L705, 706, 707, 708).

YES

OK

3-22 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
7. AUX / TUNER FUNCTION CHECK

FUNCTION CHECK

YES

Check NO
IC202 Pin27, 28, 29, 30 Check JK200, TU200.
input.

YES

Check
Check IC202 NO IC202 Pin8: ADC +3.3 V NO
Pin13,14,25: DVCC +3.3 V.
Check CN102 Pin13,14: 12 VA.
Pin18, 19 output data.

YES YES

Check IC202 Check IC202

Check NO NO Pin18,19:ADC, MIC_DATA SDOUT,
Pin8: ADC +3.3 V, Pin17: BCK, Pin16: LRCK,
IC500 input data. Pin13, 14, 25: DVCC +3.3 V. Pin15: MCLK.

YES
YES

IC500 output data. Replace IC201.

YES

OK

8. TUNER FUNCTION CHECK

TUNER FUNCTION CHECK

YES

Check tuner module(TU200) NO Check tuner module voltage

operation. (Pin4: +3.3 V).

YES

NO
Check IC500 Pin P7, P8, P10, P11. Check tuner module data.

YES

Refer to function check.

3-23 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
9. CD FUNCTION

CD FUNCTION

YES

Can the NO NO Is Motor_open/close OK?

Is load +,- ok? (IC400 Pin9,10)
disc insert?

YES
YES YES
Check IC400.

NO
Is Motor ok? (about 12 Ω) Check loading motor.

Check IC400
(Motor drive IC).

NO

NO NO Focus,
Disc reading IM driving
tracking, sled signal
is ok? (Focus and tracking) is ok?
is ok?

YES YES

Is no signal at spk? Is the MD(CN400 Pin7)

about 190 mV?

YES NO

Check NO
the signal of IC401 Check Vcc of IC401. Check IM (pick-up).
Pin52,53,54.

YES
Check
the signal (16.9344 NO NO
Check Cristal (X400). Replace Cristal (X400).
MHz) at IC401
Pin51.

YES

Check IC500 NO
input/output and Replace IC500.
control line.

YES

Refer to function check.

3-24 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 ELECTRICAL TROUBLESHOOTING GUIDE
10. DOUBLE USB FUNCTION

USB FUNCTION

YES

Plug-in USB device.

YES

NO NO
Display “NO USB”. Check USB_5V. Check CN301.

YES
YES
Check
USB1_D-/D+(R335,336) NO Check USB jack
Display “READ”. USB2_D-/D+(R301, (CN301/ CN302).
302).
YES
YES

Check IC500 NO
Display “NO FILE”. Replace IC500.
(Pin U7, U8/ A7, A8).

YES

Check USB audio file in USB device

(MP3, WMA file is playable)

3-25 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
 WAVEFORMS OF MAJOR CHECK POINT

1 CLK
5
DATA CD-16 M
2

3 ADDRESS

4 CS

Fig 1. SDRAM
Fig 2. SERVO
①IC504 pin38, ②IC504 pin53
⑤IC500 pin M1
③IC504 pin35, ④IC504 pin19

MCS_MCLK
9
6 CD_BCK

10 MCS_BCK

7 CD_LRCK
11 MCS_LRCK

8 CD_DATA
12 ADC_DATA

Fig 3-1. AUDIO PATH Fig 3-2. AUDIO PATH

⑥IC500 pin N4, ⑦ICIC500 pin N1 ⑨IC500 pin D2, ⑩IC500 pin E1
⑧ICIC500 pin N2 ⑪IC500 pin D1, ⑫IC500 pin E2

USB_5 V

13
D+

D-
14

Fig 4. USB
⑬IC500 pin A8, ⑭IC500 pin A7

3-26 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
WIRING DIAGRAM

SPK_L LED SPK_R LED

4P 4P
AUX I n Tuner FL RL WF

I C202 I C204
ADC EXPENDER 3P

10P
10P
I C401
RF I C I C500

MD AM5
589
89

I C400
SMPS
23P
23P

Mot or DR I C700

14P B TO B
14P B TO B
I C501 I C504 PWM
F/ S 32M SDRAM

MAI N
I C200
8P
8P

8P 17P 10P
USB

MI C PTB

BT
8P 17P
JACK USB modul e Har ness

FFC
FRONT
USB1 USB2

3-27 3-28 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
BLOCK DIAGRAMS
1. SYSTEM BLOCK DIAGRAM
2. 0 1. 1
CD_RST USB1 USB2
( VCC50) A, B, C, D, E, F, PD SERVO
LD
I C401 ANALOG I NPUT Bl ock
P/ UP ( 4 X)
SPDO/ SLDO CD_RW/ MCLK/ LRCK/ BCK,
/ FOD/ TRD CD_DAT
AUX I N
MOT_MUTE, CLOSE, OPEN D1+/ -
I C400
M LOAD± , SLED± , Mot or Dr i ve D2S+/ -
SPI N± , TR± , F±

DECK
OP_SW, CL_SW, UP_SW, DN_SW, D_SENSE I C201
MECHANI SM FM/AM TUNER
( FM/ AM)
DRM_WEN/ CAS/
( +3. 3V_CD, VCC1. 2)
MD 16MB
RAS/ SEL/ CLK/ CKE

M00_15 PTB
SDRAM
Bl ock A00_16
I C501
ADC_DATA

Mai n DSP For AUX MCS_BCK/ LRCK/ MCLK

1MB SF_DI / DO
Fl ash SF_CS/ SCK

4MB I C200 MI C
S/ Fl ash SF_DI / DO
SF2_CS/ SCK

PWM_LRCK/ BCK/ DATA

( +3. 3VA, 5V, +12V)

FRONT LPF
FRONT( BTL)

IR RMC
Recei ver PWM AMP
I C700 I C702 FRONT( BTL)

VFD_STB/ CLK/ DO/ RST,

VFD CK57 Only
LPF SW(PBTL)
Vol ume/ MAI N VOL_A/ B , Sear ch A/ B, KEY AMP
Sear ch A/ B I c701
Key

Speaker PWM + AMP Bl ock

FRONT Bl ock Li ght i ng
[CK57 : Total 2.1ch 1100W
350+350+400]
[CK56 : Total 2ch 700W]

3-29 3-30 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
2. POWER BLOCK DIAGRAM

5.1 VA 1.2 VA
Pull up
+12 VA IC102 IC101
150 mA Resistance 11 mA EXPENDER
2.2 A 37 mA
MAIN DSP 80mA SPK LED
1.5 A
20 mA IC500 25 mA
3.3 VA RF IC401
IC100
486 mA 486 mA
163 mA
IC700
32 mA
P-SENSE BT MODULE 25 mA MIC AMP
0.7 mA IC200
RMC 31 mA
MIC ADC
105 mA IC202
F/S + SDRAM
1 mA
RESET IC 5 mA
VFD
328 mA DVCC_3.3V 40 mA
IC103 TUNER
300mA
1000 mA
USB1
SMPS
IC104
USB2

100 mA
SPK LED

350 mA MOTO DRIVE

680 mA DVCC_5V IC400
IC105 80 mA
680 mA VFD F+/ -
70 mA
VFD 150 mA
300 mA CD PICK UP
TR Switching 300 mA
FAN
12 V

100 mA
PVDD 100 mA IC701
TR Switching
48V Amp 12 V
IC702

3-31 3-32 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
CIRCUIT VOLTAGE CHART
1. CONNECTORS
Pin No. Pin Name Spec [%] Range [%] CABLE Input Voltage Margin [%] CABLE Output Voltage Margin [%]
MAIN <-> SMPS (BtoB) CN902 (SMPS) CN102 (MAIN)
5,6,7 PVDD 45 ±10% 43.71 -2.9% 43.72 -2.8%
13,14 12 VA 12 ±10% 12.05 0.4% 12.06 0.5%
MAIN <-> USB (Harness) CN502 (MAIN) CN301 (FRONT)
1,2 USB_5V 5.1 ±10% 5.2 2.0% 5.2 2.0%
MAIN <-> BT Module (FFC) CN5101 (MAIN) BT Module
1 VDD 3.4 ±10% 3.37 -0.9% 3.37 -0.9%
MAIN <-> FRONT (FFC) CN101 (MAIN) CN300 (FRONT)
1 DVCC_3.3V 3.4 ±10% 3.34 -1.8% 3.36 -1.2%
2 LED_5V 5.1 ±10% 5.18 1.6% 5.16 1.2%
4 12VA_VFD 12 ±10% 12.03 0.2% 12.02 0.2%
6 3.3VA 3.4 ±10% 3.4 0.0% 3.39 -0.3%
MAIN <-> MD (Pick-up) CN400 (MAIN) MD
8 VCC 5 ±10% 5.21 4.2% 5.18 3.6%

2. CAPACITORS 3. ICs
SYMBOL Capacity (uF) SPEC Voltage (V) SPEC -20 % (88 V, 60 Hz) +20 % (288 V, 60 Hz)
Location No.
C121 220 16 3.04 (V, mV) (V) (V)
C134 100 16 5.17 IC100, IC101 Vin : -0.3 ~ 7 Vin : 5.17 Vin : 5.17
C169 100 16 12.02 DC, DC Converter Vsw : -0.3 ~ Vin : +0.3 Vsw : 2.4 Vsw : 2.4

C260 100 16 5.16 IC102

VIN : 4.2~17 V VIN : 11.98 VIN : 11.98
DC, DC Converter
C308 47 16 3.28
IC103 Vin : 2.5 ~ 5.5 V Vin : 3.35 Vin : 3.35
C309 47 16 3.04 Analog Switch Vout : 0 ~ 5.5 V Vout : 0~5.5 V Vout : 0 ~ 5.5 V
C331 100 16 0.18 IC104, IC105 Vin : -0.3 ~ 6 V Vin : 5.15 V Vin : 5.15 V
C332 100 16 0.18 Analog Switch Vout : -6 ~ 6 V Vout : 5.12 V Vout : 5.12 V
C333 47 16 3.34 IC200
VDD : 3 ~ 3.6 V VDD : 3.32 V VDD : 3.32 V
Line Driver
C334 47 16 12.01
IC202 AVDD : -0.3 ~ 3.9 V AVDD : 3.309 V AVDD : 3.309 V
C339 47 16 5.15
A/D Converter DVDD : -0.3 ~ 3.9 V DVDD : 3.31 V DVDD : 3.31 V
C402 100 16 5.16
IC204
C411 47 16 3.27 VCC : 3.0 ~ 5.5 V VCC : 3.31 V VCC : 3.31 V
LED Driver
C418 3.3 50 1.173 IC400
VCC : 4.3 ~ 13.2 V VCC : 5.14 V VCC : 5.14 V
C421 47 16 1.65 Motor Driver
C447 220 16 5.14 IC401 DVDD,AVDD : 2.7 ~ 3.6 V DVDD, AVDD : 3.3 V DVDD, AVDD : 3.3 V
RF Amplifier VDD_CORE : 1.4 ~ 1.65 V VDD_CORE : 1.53 V VDD_CORE : 1.53 V
C766 680 63 44.1
IC500 VDD12 : 1.08 ~ 1.32 V VDD12 : VDD12 :
C767 680 63 44.1 Digital Signal Processors VDD33 : 3.0 ~ 3.6 V VDD33 : 3.30 V VDD33 : 3.30 V
C770 680 63 44.1 IC501
Vcc : 2.7 ~ 3.6 V Vcc : 3.35 V Vcc : 3.35 V
C771 680 63 44.1 Serial Flash Memory
C903 330 109 IC502
VDD: 1 ~ 7 V VDD: 3.35 V VDD: 3.35 V
C904 330 109 Reset

C909 22 16 IC503
Vcc : 2.7 ~ 3.6 V Vcc : 3.35 V Vcc : 3.35 V
Serial Flash Memory
C911 47 22
IC504
C914 10 21 VDD, VDDQ : 3.0 ~ 3.6 V VDD, VDDQ : 3.38 V VDD, VDDQ : 3.38 V
SDRAM
C933 1000 12 IC700 DVDD : 3.0 ~ 3.6 V DVDD : 3.30 V DVDD : 3.30 V
C934 470 12 Sound/Audio Processor AVDD : 3.0 ~ 3.6 V AVDD : 3.30 V AVDD : 3.30 V
C952 2200 43 PVDD : 25 ~ 52.5 V PVDD : 43.7 V PVDD : 43.7 V
IC701, IC702
GVDD : 10.8 ~ 13.2 V GVDD : 11.98 V GVDD : 11.98 V
C953 2200 43 Audio Amplifier
VDD : 10.8 ~ 13.2 V VDD : 11.99 V VDD : 11.99 V

3-33 3-34 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
PRINTED CIRCUIT BOARD DIAGRAMS
1. SMPS P.C.BOARD DIAGRAM
(TOP VIEW) (BOTTOM VIEW)
NOTE) Warning
Parts that are critical with respect to risk
of fire or electrical shock.

3-35 3-36 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
2. MAIN P.C.BOARD DIAGRAM
(TOP VIEW) (BOTTOM VIEW)

3-37 3-38 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
3. FRONT P.C.BOARD DIAGRAM
(TOP VIEW)

(BOTTOM VIEW)

3-39 3-40 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.
4. MIC P.C.BOARD DIAGRAM
(TOP VIEW) (BOTTOM VIEW)

3-41 3-42 Copyright © 2018 LG Electronics Inc. All rights reserved.

Only for training and service purposes.