Xoceco LC-37W18S Schematic

LCD TELEVISION

LC-37W18S

CONTENTS

Safety precautions………………………………………………………………………..…

Alignment instructions …………………………….…….…………………………….…

Method of software upgrading ………………………………………….…….……………

Working principle analysis of the unit……………………………….………….………….

Block diagram…………………………………..……………………………….…………

IC block diagram………………………………………………………………………..……

Wiring diagram ……………………………………………………………………………..

Identification criteria for the bright spot and dark spot of the LCD screen………..….

Troubleshooting…………………………………………………………………………..……

Schematic diagram …………………………………………………………………….…..

Appendix A: Assembly list
Appendix B: Exploded view

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13

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Attention: This service manual is only for service personnel to take reference with. Before

servicing please read the following points carefully.

Safety precautions

1. Instructions

Be sure to switch off the power supply before replacing or welding any components or
inserting/plugging in connection wire Anti static measures to be taken (throughout the entire
production process!):
a) Do not touch here and there by hand at will;
b) Be sure to use anti static electric iron;
c) It’s a must for the welder to wear anti static gloves.
Please refer to the detailed list before replacing components that have special safety requirements.
Do not change the specs and type at will.

2. Points for attention in servicing of LCD

2.1 Screens are different from one model to another and therefore not interchangeable. Be sure to
use the screen of the original model for replacement.

2.2 The operation voltage of LCD screen is 700-825V. Be sure to take proper measures in
protecting yourself and the machine when testing the system in the course of normal operation or
right after the power is switched off. Please do not touch the circuit or the metal part of the module
that is in operation mode. Relevant operation is possible only one minute after the power is
switched off.

2.3 Do not use any adapter that is not identical with the TV set. Otherwise it will cause fire or
damage to the set.

2.4 Never operate the set or do any installation work in bad environment such as wet bathroom,
laundry, kitchen, or nearby fire source, heating equipment and devices or exposure to sunlight etc.
Otherwise bad effect will result.

2.5 If any foreign substance such as water, liquid, metal slices or other matters happens to fall into
the module, be sure to cut the power off immediately and do not move anything on the module lest it
should cause fire or electric shock due to contact with the high voltage or short circuit.

2.6 Should there be smoke, abnormal smell or sound from the module, please shut the power off at
once. Likewise, if the screen is not working after the power is on or in the course of operation, the
power must be cut off immediately and no more operation is allowed under the same condition.

2.7 Do not pull out or plug in the connection wire when the module is in operation or just after the
power is off because in this case relatively high voltage still remains in the capacitor of the driving
circuit. Please wait at least one minute before the pulling out or plugging in the connection wire.

2.8 When operating or installing LCD please don’t subject the LCD components to bending, twisting
or extrusion, collision lest mishap should result.

2.9 As most of the circuitry in LCD TV set is composed of CMOS integrated circuits, it’s necessary
to pay attention to anti statics. Before servicing LCD TV make sure to take anti static measure and
ensure full grounding for all the parts that have to be grounded.

2.10 There are lots of connection wires between parts behind the LCD screen. When servicing or
moving the set please take care not to touch or scratch them. Once they are damaged the screen

1

would be unable to work and no way to get it repaired.
If the connection wires, connectors or components fixed by the thermotropic glue need to disengage
when service, please soak the thermotropic glue into the alhocol and then pull them out in case of
damage.

2.11 Special care must be taken in transporting or handling it. Exquisite shock vibration may lead to
breakage of screen glass or damage to driving circuit. Therefore it must be packed in a strong case
before the transportation or handling.

2.12 For the storage make sure to put it in a place where the environment can be controlled so as to
prevent the temperature and humidity from exceeding the limits as specified in the manual. For
prolonged storage, it is necessary to house it in an anti-moisture bag and put them altogether in one
place. The ambient conditions are tabulated as follows:

Temperature Scope for operation 0 ~ +50 oC

Scope for storage -20 ~ +60 oC

Humidity Scope for operation 20% ~ 85%

Scope for storage 10% ~ 90%

2.13 Display of a fixed picture for a long time may result in appearance of picture residue on the
screen, as commonly called “ghost shadow”. The extent of the residual picture varies with the
maker of LCD screen. This phenomenon doesn’t represent failure. This “ghost shadow” may remain
in the picture for a period of time (several minutes). But when operating it please avoid displaying
still picture in high brightness for a long time.

3. Points for attention during installation

3.1 The front panel of LCD screen is of glass. When installing it please make sure to put it in place.

3.2 For service or installation it’s necessary to use specified screw lest it should damage the screen.

3.3 Be sure to take anti dust measures. Any foreign substance that happens to fall down between
the screen and the glass will affect the receiving and viewing effect

3.4 When dismantling or mounting the protective partition plate that is used for anti vibration and
insulation please take care to keep it in intactness so as to avoid hidden trouble.

3.5 Be sure to protect the cabinet from damage or scratch during service, dismantling or mounting.

2

Alignment instructions

y

1. Test equipment

PM5515 (Video signal generator)
PM54200(SCART signal generator)
VG-848(YUV, VGA and DVI signal generator)
K-7253 (VGA signal generator)
CA210 (White balancer)

2. The alignment flow chart (see below figure)

Production of data processing board and

Combined test for general assembly and aging

Connect to central signal source; check if various

TV functions (station skipping, modulate quantit

control etc), check if the output of earphone and

speaker are normal.

Input AV/S signal, SCART and HDTV signal;
check various functions under AV/S terminal

Input VGA signal and check if display is normal in

the state of PC and various functions (analog

quantity control, line/field center etc.)

Fig.1 Flow process of alignment

3 Unit adjustments

Method for entering factory menu: Press MENU → -/-- →9→1→8 one by one, then enter factory
menu, press the SLEEP button to select adjustment page, exit factory menu to press the MENU
button.

Check DDC and FLASH

analogue board on the line.

White balance adjustment

Check accessories and then packing

3

4 EEPROM initialization

Enter the first page of factory menu, select “EEPROM INITIALIZE” to be “on”, after turn off the unit,
repeating turn on the unit is over.

5 white balance adjustment

Input PAL signal of 16-level gray-scale (TIMING969 PATTAN921) from VG848 to AV channel, enter
user menu, set color to 0, APL to “off”, enter factory menu white balance adjustment page, select
color temperature, fixed the GGAIN to 50H, adjust BGIAN and RGAIN to 400nits, then the color
coordinate to 284, 299. Fixed the BOFFSET to 50H, adjust GOFFSET and ROFFSET to 5nits, then
the color coordinate to 284, 299.
Select cool tint, adjust color coordinate to 270, 283.
Select warm tint, adjust color coordinate to 313, 329.

6. Performance Inspections

6.1 TV function
Enter the search menu → auto search, connect RF-TV terminal to the central signal source, check if
there is station skipping.

6.2 AV/S input terminal
Input AV/S signal, check the picture and sound is normal

6.3 SCART terminal (note: check the SCART terminal, set display mode to AUTO)

6.3.1 Check SCART INPUT special function

6.3.1.1 SCART1 terminal function
a. After turn on the unit, connect the SCART1 to PM54200 signal generator, then the unit auto
select to SCART1 mode.
b. SCART signal generator sends CVBS signal to the unit, check if the image and sound is normal.
It sends image format (16:9 and 4:3) to the unit, check if the unit auto identify is normal. Change
SCART signal to RGB signal, check if the image and sound is normal, It sends image format (16:9
and 4:3) to the unit, check the unit auto identify is normal. Select the PIP mode, connect earphone
cable, and check if the sound is normal.

6.3.1.2 SCART2 terminal function
a. After turn on the unit, connect the SCART2 to PM54200 signal generator, then the unit auto
select to SCART2 AV mode.
b. SCART signal generator sends CVBS signal to the unit, check if the image and sound is normal.
It sends image format (16:9 and 4:3) to the unit, check if the unit auto identify is normal, and display
the SCART2 AV. Change SCART signal to Y/C signal, select the SCART2 Y/C channel mode,
check if the image and sound is normal, It sends image format (16:9 and 4:3) to the unit, check if the
unit auto identify is normal. Select the PIP mode, connect earphone cable, and check if the sound is
normal.

6.3.2 Check SCART OUTPUT special function

6.3.2.1 SCART1 terminal function
Input signal in the TV states, connect the SCART1 terminal to the TV. Change the TV program,
check if output signal of SCART1 is TV signal, and the image and sound is normal, change the unit
channel, the CART1 output TV signal, it can not other signal.

6.3.2.2 SCART2 terminal function

4

Input signal in the TV/AV/S states, connect the SCART2 terminal to the TV. Change the unit channel,
check if output signal of SCART2 is current signal, and the image and sound is normal.

6.4 YPbPr/YPbPr terminal
Input the YUV signal (VG-848 signal generator), separate input YUV format signal of table 1, check
if the image and sound is normal. If the image is deflection of the H-field, select auto sync correction
of the SCREEN menu. If the image is slight disturb, adjust the FINE TUNE correction of the
SCREEN menu. Open the PIP mode, connect the earphone, and check if the image and sound is
normal.

Table 1 YUV format signal

H-frequency(kHz) V-frenquency(Hz) signal
1 15.734 59.94 SDTV 480i

2 31.469 59.94 HDTV 480p
4 44.955 59.94 HDTV 720p
6 33.716 59.94 HDTV 1080i
7 15.625 50 SDTV 576i
8 31.25 50 HDTV 576p
9 33.75 50 HDTV 1080i

10 37.50 50 HDTV 720p

6.5 VGA terminal

Input the VGA signal (VG-848 signal generator), separate input VGA format signal of table 1, check
if the image and sound is normal. If the image is deflection of the H-field, select auto sync correction
of the SCREEN menu. If the image is slight disturb, adjust the FINE TUNE correction of the
SCREEN menu. Open the PIP mode, connect the earphone, and check if the image and sound is
normal.

6.6 HDMI terminal
HDMI signal format receive the three high definition signal: 480P, 576P, 720P/50/60 Hz, 1080I/50/60
Hz, except for the table 2 signal. Check if the image (contain HDCP ON and OFF) and sound is
normal. If the image is deflection of the H-field, select auto sync correction of the SCREEN menu.
Open the PIP mode, connect the earphone, and check if the image and sound is normal.

TABLE2 VGA signal format

resolution H-frequency(kHz) V-frenquency(Hz)

Point clock pulse

frenquency(MHz)

remark

1 720 X 400 31.469 70.086 28.322 IBM
2 640 X 480 31.469 59.94 25.175 IBM
3 640 X 480 37.861 72.809 31.5 VESA
4 640 X 480 37.5 75 31.5 VESA
5 640 X 480 43.269 85.008 36 VESA
6 800 X 600 35.156 56.25 36 VESA

7 800 X 600 37.879 60.317 40 VESA
8 800 X 600 48.077 72.188 50 VESA

9 800 X 600 46.875 75 49.5 VESA
10 800 X 600 53.674 85.061 56.25 VESA
11 1024 X 768 48.363 60.004 65 VESA

5

12 1024 X 768 56.476 70.069 75 VESA
13 1024 X 768 60.023 75.029 78.75 VESA

14 1280 X 1024 63.98 60.02 108.00 VESA
15 1024 X 768 68.667 84.98 94.486 VESA

6.7 ex-factory setting see to TABLE 3 - TABLE 9

TABLE 3 Factory Option Menus

Items Ex-factory setting

IIC Bus-off Off

EEPROM Erase Off

Backlight Adjustable Off

Back Light 100

Menu Timeout 5

Blank switch enable On

ShowLogo On

Auto Program Sort On

TT Char Group

West Europe / East Europe / Cyrillic / Turkish

/Greek/Arabic/Hebrew
Dynamic Scart Off
Note: the latter 6 items should set according to clients’ require.

TABLE 4 Factory Audio Setting

Items

Ex-factory setting

LC-27W18S/27W25S LC-32W25S LC-37W25S LC-42W17S

Volume 1 2CH 2CH 2CH 2CH
Volume 25 55H 57H 5AH 5AH
Volume 50 5CH 5EH 61H 61H
Volume 75 64H 65H 69H 69H
Volume 100 6BH 6DH 72H 72H

HP VOLUME SETTING

Volume 1 64H
Volume 25 96H
Volume 50 A1H
Volume 75 AEH
Volume 100 BEH
MSP Scart1 Volume 72H

Prescale Scart 4CH
Prescale FM/AM 27H
Prescale Nicam 64H

Scart TV Volume 20H

Scart AV Volume 72H

6

D/K select HDEV3 Off
AVC Of f

Equalizer Bands Max 60H
Spatial Mode 0
Spatial Strength 00H

TABLE 5 Factory Video limit Setting

Items CVBS SC-RGB YPBPR D-SUB HDMI
Bright Min D5H CFH C7H CFH D2H

Bright Middle 00H 00H 03H 05H 07H
Bright Max 38H 3DH 34H 3DH 31H

Contrast Min 09H 09H 09H 09H 08H
Contrast Middle 20 25H 20H 25H 23H
Contrast Max 2AH 31H 29H 31H 2CH

Sharpness Min 00H 00H 00H 00H 00H
Sharpness
Middle

10H 10H 10H 10H

10H

Sharpness Max 1FH 1FH 1FH 1FH 1FH

Color Min 00H 00H 00H 00H 00H

Color Middle 1DH 1DH 1DH 1DH 1DH
Color Max 2DH 2DH 2DH 2DH 2DH

Hue Min 80H 80H 80H 80H 80H
Hue Middle 20H 20H 20H 20H 20H
Hue Max 7FH 7FH 7FH 7FH 7FH

TABLE 6 White Balance Adjust

Items LC-27WXXS LC-32WXXS LC-37WXXS LC-42WXXS
R Offset 55 55 54 53
G Offset 51 53 57 49
B Offset 50 50 50 50
R Gain 42 36 36 37

G Gain 50 50 50 50
B Gain 21 40 51 38
Brightness 51 51 51 51
Contrast 100 100 100 100
Color Temperature Standard

R Offset 60 59 58 55
G Offset 55 55 58 52

7

B Offset 50 50 50 50
R Gain 35 25 24 32

G Gain 50 50 50 50
B Gain 28 48 61 48
Brightness 51 51 51 51
Contrast 100 100 100 100
Color Temperature Cold

R Offset 55 49 49 44
G Offset 53 51 53 47
B Offset 50 50 50 50
R Gain 62 51 58 66
G Gain 50 50 50 50
B Gain 8 23 33 22

Brightness 51 51 51 51
Contrast 100 100 100 100
Color Temperature Warm

TABLE 7 Image analog setting

CVBS Vivid Standard Mild Custom
Contrast 90 80 50 80

Brightness 40 35 35 35
Color 70 60 40 60
Hue 00 00 00 00
Sharpness 60 50 30 50

SC-RGB Vivid Standard Mild Custom
Contrast 90 85 50 85

Brightness 60 50 35 50
Color 80 65 40 65
Hue 00 00 00 00
Sharpness 60 50 30 50

YPBPR Vivid Standard Mild Custom
Contrast 90 85 50 85

Brightness 50 40 35 50
Color 80 65 40 65
Hue 00 00 00 00
Sharpness 60 50 30 50

D-SUB Vivid Standard Mild Custom
Contrast 90 80 50 80

Brightness 50 40 35 40
Color 80 65 40 65
Hue 00 00 00 00
Sharpness 60 50 30 50

8

HDMI Vivid Standard Mild Custom
Contrast 90 80 50 80

Brightness 50 35 35 35
Color 80 70 40 70
Hue 00 00 00 00
Sharpness 60 50 30 50
Note: in factory menu states, it can change the factory mode to value of the image and sound,
else select the image and sound balanced value in the other states.

TABLE9 SOUND equilibrium value setting

Live Pop Rock Custom
120 Hz 50 50 65 50
500 Hz 50 50 55 50

1.5 kHz 50 60 55 50
5 kHz 80 70 55 50
10 kHz 85 70 55 50

6.8 Ex-factory setting of user menu

6.8.1 select TV channel

6.8.2 video menu, Mode: Standard, NR: Medium, APL:ON

6.8.3 sound menu, Volume: 20, Balance: 00, Equalizer: Custom, HP Volume: 20;

6.8.4 edit menu, Color System: Auto, Sound System: DK;

6.8.5 option menu, Default Zoom: Auto, Child Lock: Off, Menu Language: English, Country: UK,
WSS: OFF, Blue Screen: On.
Note: the 6.8.4 and 6.8.5 items should set according to clients require.

9

Method of software upgr adi ng

1. Enter the software upgrading state of the TV
Method 1: press the VOL- button in the unit, turn on the main power switch, then the screen

display black screen, but the indicator to blue.

Method 2: Enter factory menu, select the IIC-BUS OFF item.

2. Connection upgrading tools with upgrading port.

3. Dual- click IAPWriter logo, enter the upgrading states (if the PC and the IIC communication

trouble, it can prompt.

4. Select the file menu load the software follow as:

10

5. Select WRITE DEVICE item of the device menu, till the right screen display “DONE”.

6. turn off the power , restart the unit.
Note: because of the software, it may be no-stabilization, the software can auto download
and write.

Upgrading tools

Connection cable

11

Upgrading port

NOTE: Do not shut the power off or turn the TV set on during the FLASH write. Otherwise it may
lead to no way for flash to rewrite.

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Working principle analysis of the unit

1. Analog signal flow
Antenna reception signal send to integrative tuner (contain HF and IF amplifier circuit), the tuner is
controlled the command (SDA and SCL) of the MCU N301 (M16C), select appropriate channel to
system switch, via HF amplifier and IF amplifier decode, output video signal of 2VPP and sound
signal of 1VPP.
Sound signal (SCART1, 2 sound, AV sound, YPbPr, HDMI and D-SUB) via N581 HEF4052BT
(sound diverter switch) to output signal, it send to N801(MPS3410 sound processing and volume
control) switch of audio. Select right/left sound channel, their send to digital sound amplifier N803
(TPA3008) amplify, then send to speaker.
After output video signal of tuner, SCART1 video signal and RGB signal via matched resistance, the
signal thought alone channel send to main decode IC(N101 SVP-EX52) video switch, A/D
transition, digital decode, image scale and OSD superposition, then send to LVDS level drive for
LCD screen.
AV, S-Video, SCART2 video and Y/C signal thought matched resistance, the signal send to the
N506 video switch (SN74CBT3257CDR), via switching to selected signal (EX52_Y and EX52_C) to
main decode IC (N101 SVP-EX52) video switch, A/D transition, digital decode, image scale and
OSD superposition, then send to LVDS level drive for LCD screen.
D-sub and YPbPr signal thought matched resistance, the signal send to the N507 video switch
(SN74CBT3257CDR), via switching to selected signal (EX52_YUV) to main decode IC (N101
SVP-EX52) video switch, A/D transition, digital decode, image scale and OSD superposition, then

send to LVDS level drive for LCD screen.

2. Digital signal flow:
HDMI signal thought HDMI reception chip N405 (SiI9011HDMI with HDCP function), after receive,
output digital format signal send to SVP-EX52 PIP channel thought image scale and OSD
superposition, then send to LVDS level drive for LCD screen. The HDMI chip output audio digital
format signal change to analog sound signal from N403 (CS4344 audio DA transfer chip), then
N581 switched to N801 (MPS3410 sound processing and volume control).

3. TELETEXT function
This unit adopt main decode IC N101(SVP-EX52) of Trident company, it has TELETEXT decode
function, after decoded, the teletext information in OSD display.

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Block diagram

14

IC block diagram

1. Sound processing IC (MSP3410)

Sound signal send to sound processing N801 MSP3410, and dual-circuit tuner has second SIF, it
sends to N801 (stereo decode and auto volume control), N801 has audio channel switch, after
switching in N581 (HEF4052BT), the audio input of VGA/HDMI/YPbPr will be sent to N801 together
with the audio signal of TV and AV to do the switching process. A way signal thought volume and
high-low sound controlled, output the left and right audio send to digital audio amplifier N803
(TPA3008) amplify, then it send to speaker, other way signal output left-right audio send to
earphone amplifier N805 (NJW1109), after audio control and power amplifier, it output to earphone
socket. Other two ways signal output audio of TV out and AV out by SCART terminal of video board.

MSP3410 internal block diagram as follow:

Main pins instructions:
2, 3: SCL, SDA
27, 28: left-right audio of audio power amplification
36, 37: left-right audio of earphone
24, 25: left-right audio of AV OUT
33, 34: left-right audio of TV OUT
47, 48: left-right audio from main board
50, 51: left-right audio of SCART2
53, 54: left-right audio of SCART1
56, 57: left-right audio of AV IN
67, 69: SIF input of sub-channel and main-channel TV
59: MONO input of sub-channel TV

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2. Sub-channel and SCART video signal decode IC (TVP5147)

Sub-tuner TUNER202 decode video, AV, S-VIDEO, SCART1 video, SCART2 video and Y/C signal,
after matching impedance, enter decoding IC N601 (TVP5147), so the PIP image of sub-channel
can selecting arbitrary video signal.

MSP3410 internal block diagram as follow:

TVP5147 main pins instructions:
28, 29: SCL, SDA
22: Video input for SCART1
7, 80: Y/C signal input for SCART2
16: video signal input of sub-tuner
8: Y signal input of AV or S-Video
1: C signal input of S-Video
9, 2, 18: YUV signal input of compatible DTV

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3. Reception HDMI signal (Si I 9011)

After differential signal of HDMI send to N405 (SiI9011), then it transform 24bit for video digital
signal, and sent to IC N101 (SVP-EX52) processing.

SiI9011 internal block diagram as follow:

4. Main decode and processing IC(DPTV-SVP-EX52)

SVP-EX52 internal block diagram as f ollow:

17

SVP-EX52 main pins instructions:

14, 16: SCL, SDA
10, 11: VGAHS, VGAVS input,
244, 231: EX52_Y and EX52_C input
243: main tuner video signal input
242: video signal input for Scart1
226, 248, 233: Scart1 RGB input
246, 232, 225: EX52_YUV input
236, 237: video output for SCART2

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Wiring diagram

19

Identification criteria for the bright spot and dark spot of the LCD screen

Category criteria

One single

spot

Bright

spot

Dark

spots

Total defected point ≤8 ≤7 ≤5 ≤4 /

Two

neighboring

spots

Tota l No . ≤5 ≤2 ≤5 ≤2 ≤3

One single

spot

Two

neighboring

spots

Tota l No . ≤6 ≤7 ≤5 ≤4 ≤10

15" 20" 22" 30" 40" 15" 20" 22" 30" 40"

≤5 ≤2 ≤5 ≤2 ≤3

≤2 ≤1 ≤2 ≤1 ≤1

≤6 ≤7 ≤5 ≤4 ≤10

≤2 ≤2 ≤2 ≤1 ≤5

Notes:

1. Definition of defected point (bright spot, dark spot): It is identified as a defected point if its area
exceeds 1/2 of a single picture element (R, G, B).

2. Definition of bright spot: It is identified as a bright spot if it is bright in the state of dark field and its
bright size remains unchanged

3. Definition of dark spot: It is identified as a dark spot if it is dark in the state of white field and its
dark size remains unchanged

4. Definition of two neighboring points: Defects of a group of picture elements (RB,RG,GB).

quantity allowed Distance between two spots

≥15mm

≥15mm

≥10mm ≥5mm

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Trouble shooting

1. Fault clearance

Before servicing please check to find the possible causes of the troubles according to the table

below.

1.1 Antenna (signal):

Picture is out of focus or jumping  Bad status in signal receiving

 Poor signal

 Check if there are failures with the electrical connector or

the antenna.

 Check if the antenna is properly connected.

Fringe in picture  Check if the antenna is correctly oriented.

 Maybe there is electric wave reflected from hilltop or

building.

Picture is interfered by stripe shaped

bright spots

There appear streaks or light color

on the screen

1.2 TV set:

Symptoms Possible cause

Unable to switch the power on  Check to see if the power plug has been inserted properly

No picture and sound  Check to see if the power supply of liquid crystal TV has

Deterioration of color phase or color

tone

Screen position or size is not proper  Check is the screen position and size is correctly set up.

Picture is twisted and deformed  Check to see if the picture-frame ratio is properly set up.

Picture color changed or colorless  Check the “Component” or “RGB” settings of the liquid

 Possibly due to interference from automobile, train, high

voltage transmission line, neon lamp etc.

 Maybe there is interference between antenna and power

supply line. Please try to separate them in a longer

distance.

 Maybe the shielded-layer of signal wire is not connected

properly to the connector.

 Check if interfered by other equipment and if interfered

possibly by the equipment like transmitting antenna,

non-professional radio station and cellular phone.

into the socket.

been switched on. (As can be indicated by the red LED at

the front of the TV set)

 See if it’s receiving the signal that is transmitted from other

source than the station

 Check if it’s connected to the wrong terminal or if the input

mode is correct.

 Check if the signal cable connection between video

frequency source and the liquid crystal TV set is correct.

 Check if all the picture setups have been corrected.

crystal TV set and make proper adjustment according to the

21

signal types.

Picture too bright and there is

distortion in the brightest area

Picture is whitish or too bright in the

darkest area of the picture

No picture or signal produced from

the displayer if “XXX in search”

appears.

There appears an indication -

“outside the receivable scope)

Remote control cannot work

properly

No picture and sound, but only

hash.

Blur picture  Check if the antenna cable is correctly connected.

No sound  Check if the “mute” audio frequency setting is selected.

When playing VHS picture search

tape, there are lines at the top or

bottom of the picture.

 Check if the contrast setting is too high.

 Possibly the output quality of DVD broadcaster is set too

high.

 It maybe also due to improper terminal connection of the

video frequency signal in a certain position of the system.

 Check if the setting for the brightness is too high

 Possibly the brightness grade of DVD player (broadcaster)

is set too high.

 Check if the cable is disconnected.

 Check if it’s connected to the proper terminal or if the input

mode is correct.

 Check if the TV set can receive input signal. The signal is

not correctly identified and VGA format is beyond the

specified scope.

 Check if the batteries are installed in the reverse order.

 Check if the battery is effective.

 Check the distance or angle from the monitor.

 Check if there is any obstruct between the remote control

and the TV set.

 Check if the remote control signal- receiving window is

exposed to strong fluorescence.

 Check if the antenna cable is correctly connected, or if it

has received the video signal correctly.

 Of if it has received the right video signal.

 Check if the sound volume is set to minimum.

 Make sure the earphone is not connected.

 Check if the cable connection is loose.

 When being played or in pause VHS picture search tape

sometimes can’t provide stable picture, which may lead to

incorrect display of the liquid crystal TV, In this case please

press “auto” key on the remote control so as to enable the

liquid crystal TV set to recheck the signal and then to

display correct picture signal

22

2. Troubleshooting guide

d

oes bac

t

h

e

h

N

r

d

n

r

d

k

d

f

f

h

No

A red indicator lights?

Yes, turn the unit on

No

A blue indicator lights?

Yes

D

klight light up

Yes

No

Check if the display of eac
channel’s video signal is normal

Check if the display of eac
channel’s audio signal is normal

( 1) , No raster, no picture and no sound

Is the power indicator lights?
Yes No

Is the blue indicato
lights?

No Yes Normal Abnormal

Check the power supply
of CPU(N301) an
FLASH(N302)

Abnormal Normal Normal Abnormal

Check the capacitor o
L301 and the periphery o
CPU and FLASH

Connect the power

o raster, no picture and no sound

Check I2C
bus of the
system

Check the pin 10
of CPU is hig

Check Power supply, infra-red board, CPU an
its periphery circuit (flash) and power cord

Check if the pin 42 of CPU is square-wave; check
the periphery circuit of CPU and FLASH/SRAM

Check backlight board, CPU pin 77-backligh

No

control condition.

Check the signal inputted from the channel to pin IC

is normal or IC and its periphery is normal or th
output of LVDS is normal

Check the signal inputted from the channel to pin IC

No

is normal or IC(TPA3008D2/MSP3410) and its
periphery is normal

Check Standby5V

Disconnect the power supply board

with the data processing board, an
then measure Standby5V

Disconnect CN902, and the
find out that which part fails
to work properly

23

The powe
supply boar
fails to wor
properly

y

y

f

N

N

N

d

p

d

p

U

Yes No

Check if pin 42 o

No Yes

NOTE: When pin 10 of N301 is low level, remove V301 and then check the correspondent pins of

N301are high level or not, the reset circuit fails to work properly if it is high level. If pin 42 of N301 has

no square-wave, remove R365, if the square-wave appears, then it is probably the FLASH of N302 fails

to work properly. When it comes to check the periphery circuit of N301, N302 and N303, use

oscilloscope to check the connecting resistor’s pin among N301, N302and N303 besides checking the

connection of correspondent components, if regular square-wave or no signal is found, then it represents

that one of N301, N302 or N303 fails to work properly, probably is N302. If R110 and R111connects

N301 with N101fails to work will also lead to the failure phenomenon.

( 2) No picture but with sound( blue screen and OSD appear)

Yes No

Yes No

NOTE: Please refer to checking procedure (5) to get the methods for checking the phenomenon of no picture but
with sound of HDMI channel

301is square-wave

Check N301 and its crystal
oscillation

Check if other channels have no

icture

Check N101 an
its periphery

Check N301 and its reset circuit，especiall
check the critical components namel

Check the periphery circuit of

301,N3022 and N303

o picture but with soun

Whether backlight lights up.

Refer to (4) checking

rocedure

Check backlight board, CP
pin 77 backlight control

24

( 3) No picture but with sound( only backlight lights up)

N

r

f

N

k

r

p

Sound only with raster

Check if the power supply o

Normal Abnormal

Normal Abnormal

The receiving board of

LVDS fails to wor
properly

Yes No

Check the periphery circuit of N705 o

eriphery circuit of N715

NOTE: Because the power supply for 37” LG LVDS is 12V check N715 for 37” and check N705 for other models

(4), No sound but with picture

No Yes

Check if correspondent pins of powe

Yes No

Check the signal outputted from

101 to X189 is normal or not

amplifier have output

LVDS is normal or not

Check the power supply and
the periphery circuit of N101

o sound but with picture

Check if the sound processing board X804 has output

Check pin 5 of N705 or pin 2 and
4 of N715 is low level or not

Check pin 76 of N301 and the
inverter circuit, which it crosses

Speaker fails to work

25

r

d

t

h

r

p

V

f

N

t

y

Check periphery circuit

of power amplifier’s
back level

No Yes

Check if corresponden

Yes No

Check periphery circuit of

N801，crystal oscillation
and power supply circuit

( 5) , A certain channel fails to work properly

a), AV with no picture

Yes No

Yes No

b), S terminal with no picture

Yes No

Check periphery circuit of N101,
crystal oscillation and power suppl
circuit

channels of N801
have input signal

Check periphery circuit of N101,
crystal oscillation and powe
supply circuit

Check periphery circuit o

506 and power supply circui

Check if there have signals

inputted from R827 and R824 to
power amplifier

Check periphery circuit of powe

amplifier, power supply circuit an
circuit of pin MUTE

Follow the direction of audio

signal input to check eac
channel

Check if C164 has input signal

Check if pin 2 of N506 has
input signal

There exits problems at the

lace from socket of A

terminal to N506

Check if C164 and C165 have input signal

Check if pin 2 and pin 6 of N506
have input signal

28

f

d

N

y

f

r

d

l

t

p

f

N

r

Yes No

c), TV channel with no picture

Firstly find out which frame fails to work properly making use of the PIP function, PIP frame or Main

frame.

Main frame with no picture:

Yes No

Check periphery circuit of N101,
crystal oscillation and powe
supply circuit

Yes No

PIP frame with no picture:

Yes No

Check if the horizontal and vertical
synchronous signal , clock signa
outputted from N601 are normal or not

Check periphery circuit o

506 and power supply circuit

Check if C163 has input signal

Check the
circuit between
TUNER201 an

101

Check if pin 16 of N601 has inpu
signal

There exits problems at the

lace from socket of S terminal

to N506

Check if pin 12 o
TUNER201 has input signal

Check peripher
circuit o
TUNER201, powe
supply circuit an
bus

Check if pin 12 of TUNER202 has
output signal

27

d

r

N

d

N

n

n

c

ge.

Yes No Yes No

Check
surrounding
circuit, crystal
oscillation an
power supply.

d) No picture in SCART1 mode

Yes No

Check whether the connectio
between SCART1 socket pin 16
and X807 pin 9 is normal.

Yes No

Switch the signal between SCART1 RGB

Yes No

e) No picture at SCART2 mode

and VIDEO input, measure N301 pi
87 to check whether there is level

han

Check N101 surrounding

circuit, crystal oscillation
and power supply.

101

Check N601
surrounding
circuit, crystal
oscillation an
power supply.

Measure whether there is signal input to
C162,C183,C184,C185

Check N501 surrounding circuit

Measure whether there is signal input to
C164, C165.

Check the
circuit
between
TUNER202
and N601.

The trouble is at

and power supply.

Resistor R877.

There is trouble at the path
from SCART1 socket to

Check
TUNER202
surrounding
circuit, powe
supply and bus

101.

28

m

N

d

h

d

N

d

N

d

p

n

Yes No

Check N101 surrounding
circuit, crystal oscillation an
power supply.

Yes No

f) No picture at YPbPr or YCbCr mode

Yes No

Check N101 surrounding

circuit, crystal oscillatio
and power supply.

No Yes

No Yes

g) No picture in D-Sub mode

Yes No

There is trouble at the pat
between YpbPr socket an

507.

Check N506 surrounding circuit an

ower supply

Measure whether there is signal input to C173,

C174, C175.

Measure whether there is signal output fro

Check whether there is signal
input to N507 pin 2, pin 5
and pin 11.

Input YpbPr signal and check whether
the display is normal.

Measure and check whether there is signal input to

506 pin 3 and pin 6.

There is trouble at the path from
SCART2 socket to N506.

507 pin 4, pin 7 and pin 9.

Check the path from N507

output to N101 input.

Check N507 surrounding circuit an

power supply.

29

d

N

d

t

d

N

d

Yes No

Yes No

h) No picture in HDMI mode

Yes No

I) No sound in HDMI mode

No Yes

Measure whether N101

pin10, pin 11 have Sync
signal input.

There is trouble at the path
between VGA socket an

507.

Check N501 surrounding circui
and power supply.

Check N101 surrounding
circuit , crystal oscillation
and power supply.

Check and measure whether X583 pin 1 an
pin 2 output signal.

Measure whether there is sync

Check whether the H&V sync signal,
clock signal output from N405 are
normal.

signal input to N501 pin 1 an
pin 5

Check according to procedure
(f)

There is trouble at the path
between VGA socket an

501.

Check N405 surrounding circuit, power
supply and the connection to HDMI socket is
well-going.

30

r

t

h

N

t

p

)

Measure and check whether N581 pin

Yes No

Yes No

Yes No

1, pin 12 have signal input.

Check N581 surrounding

circuit and powe
supply.

Check the pat
between N403 and

Check N403 surrounding circui

and power supply.

Check whether N403 pin7
and pin10 have outpu
signal.

Check according to procedure

(4).

Check whether

403 pin1&2&3&4

Check according to

rocedure (h

31

(6) Troubleshooting guide of power supply board (32” and 37”)

a. No power supply

No power supply

Does AC voltage at C560

Y

N

Check if X501 FU501 is

properly inserted?

Does DC voltage at C529

(200~370V)

Y

N

Check D502, R530, D509

Check if the 15V DC of

N501 (pin13)

Y

N

Check N501 or peripheral

circuit

Check supplementary

power supply

b. No DC voltage output

No DC voltage output

Check if DC voltage of C535 is

5V

Check if DC voltage of V505 B
>0.6V

Check if DC voltage of C545 is

24V

Y

Y

N

N

N

Check N502 or peripheral

circuit

Check main board

Check D515, T502 or T503

(24V)

Y

Check FU503 (24V)

32

APPENDIX-A: Main assembly 9237LW1865

NAME NO.

MAIN COMPONENT AND IT'S NO.

Data processing board

Audio transform board

Video processing board
Key board
Indicator light board
IR board
Power board
Remote control
Panel

6LW0166910

6LW0121510

6LW0164010

6LW0150510

6LW0151410

6LW0150910

6LV0012010

6010I00202

5203375302

N101
N405
N601

N801
N803

RC-I02-0B

T370XW02

DPTV-SVP-EX52 （527DPTV002）
SiI9011C (5279011001)
TVP5147P (5275147001)

MSP3410G （5273410001）
TPA3008D （5273008001）

APPENDIX-B: Exploded view (LC-37X18)

PART LIST OF EXPLODED VIEW

NO. PART NO. DESCRIPTION

1 808.20358-212 ACTIVE panel
2 780.Y18L0-AW0 Front cover
3 870.10289-00 power supply bracket
4 360.30042-00 Power switch
5 700.60268-00 LED column
6 870.30216-00 LED column bracket
7 700.60255-100 LED column
8 Infrared receiving board

9 Screen
10 870.1A235-00 Board connecting bracket(right)
11 870.1A238-00 Board connecting bar(2)
12 870.1B231-00 Connecting bracket of screen(down)
13 870.10249-00 Stand bracket
14 870.1A237-00A board connecting bar
15 870.10298-00A screen connecting bracket(1)
16 video processing board
17 power board assy
18 808.10893-AF0 rear cabinet baffle(right)
19 615.20515-00 right speaker
20 digital processing board
21 808.10896-00 AV baffle (upper right)
22 808.1A898-00 AV baffle (down right)
23 808.10901-00 decorative cover
24 808.10812-AF0 power lead cover
25 615.10608-00 stand assy
26 742.30088-110 line clasp
27 808.10894-AF0 rear cabinet baffle (left)
28 808.1F897-AF0 AV baffle(down left)
29 615.20514-00 left speaker
30 808.10892-AF0 rear cabinet baffle(down)
31 808.10913-AF0 speaker connecting cover
32 808.10895-AF0 AV baffle (upper left)
33 780.Y25LHPAF2 rear cabinet
34 870.3B203-AF0 button cover bracket
35 key board
36 sound trans-connecting board
37 743.1E210-5D1 button decorative piece
38 870.10241-00 mounting holder
39 870.10242-00 mounting connecting bracket
40 870.20442-00 Connecting bar of screen
41 870.10350-00 Board connecting bracket(left)
42 870.1C230-00 connecting bracket of screen (upper)
43 870.1A236-00 brard connecting bracket

9237LW1865

Ver.1.0