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LCD TELEVISION
LC-37/42FY26
CONTENTS
Safety Precautions......................................................................................1
Alignment instructions. ............................................................................. 3
Software upgrade method............................................................................ 7
Block diagram.......................................................................................... 14
Working principle analysis of the unit............................................................ 15
IC block diagram....................................................................................... 16
Wiring diagram............................................................................................32
Troubleshooting........................................................................................ 33
Schematic diagram......................................................................................41
APPENDIX-A: Assembly list
APPENDIX-B: Exploded view
4Attention: 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.
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
1. Test equipment
Digital Multimeter, SCART signal generator FLUKE54200, Oscillograph
PC( FLASH writing program has to be installed firstly), VG848( VGA,YPBPR signal generator)
CA210 (white balancer), DVD player with HDMI output, TV set with SCART terminal
IF signal generator
2. The alignment flow chart (see below figure)
Flash writing N401, NA02, NS01, NB06, NB15
To produce main board and TV board
TV board adjustment
Check main board
Check TV board
Combined test for general assembly
Connect with central signal source, then check each function of TV such as station
missing, system identify, analog control etc., check the output of headphone and speaker
Input SCART/AV/S signal, then check each function of all the terminals
Input TV/AV/S terminal/SCART/VGA signal, and check the SCART OUTPUT at the
SCART OUTPUT situation of TV or MONITOR
Input VGA signal and check the display at PC status, check each function such as
analog control etc., check horizontal /vertical center etc.
Input HDMI signal, check if the display is normal at HDMI1 and HDMI2, check sound
and each function such as analog control etc.
Input DVB-T digital signal, check each function of the DVB-T.
3
Preset ex-factory
Check the accessories and pack them in box
Fig-1 adjustment flow-chart
3. Instruction on adjusting
3.1 Method of entering the factory menu
The method of entering the factory menu is SOURCE, 2, 5, 8, 0.
Press 1 to enter page1, the function is Cotez Feature Setting, to set LOGO, frequency ect,.
Press 2 to enter page2, the function is Color Temperature Setting. The color temperature now is
12000.
Press 3 to enter page3, the function is Auto Color setting, to set AUTO COLOR of each channel.
3.2 Writing program
Write EEPROM N401, NA02, NS01, NB06, NB15.
3.3 Main board adjustment
a) Connect X401 of main board and IR board, insert 11-pin wire of power board to XB7, then the
indicator light of IR board should be red.
b) Press POWER on the remote control, now the indicator light of IR board turns blue, test XB7
PIN1 to be 9V, PIN3 5V, PIN5/PIN6 12V, PIN9 3.3V, LB04 3.3V, NS03 PIN2 1.8V, N404 PIN2
2.5V.
c) Connect PC and serial terminal, flash write HDCP KEY.
3.4 TV board adjustment
3.4.1 IF amplify adjustment
a) Base on 3.3 a), connect 6-pin wire of power board and X04 of TV board, press POWER on the
remote control, now the indicator light of IR board turns blue, TEST PIN2 of X04 to be 5V, PIN4
9V, L07 3.3V.
b) Input +5V to TP1 and 0V to TP2, input 38.9m IF signal to J1(use IF signal generator), adjust L10
to let X08 be 1.6V.
c) Input 0V to TP1 and +5V to TP2, input 33.5m IF signal to J1(use IF signal generator), adjust
RP01 to let X08 be 1.6V.
d) Joint the tuner J1.
3.4.2 Unit connect adjustment
Connect the main board, TV board, IR board, SCART connect board and key board according to
the wiring diagram. Press POWER button on the remote control, the indicator light on IR board turns
blue, test X12 PIN1 of TV board to be +24V.
3.4.3 AGC adjustment
a) Receive 60dB signal of D-8 and test X07 with DC voltmeter.
b) Adjust RP201 to let the data of voltmeter just below 4.0V.
c) Input 100dB signal of antenna, the picture should not no-synchronous or distortion; the color
should not disappear when input 30dB-40dB low signal and the picture should synchronous and
the sound normal.
3.5 VGA adjustment
4
3.5.1 mode preset
Input VG-848 of VGA signal(PATTERN 980:1 dot ON/OFF), select TIME877(720*400/70Hz), the
TV will auto adjust to full screen, or enter display menu to do auto correction. Adjust
TIME885(640*480/60Hz,TIME854(800*600/60Hz) by using the same method.
3.5.2 VGA channel Auto color
Input VG848 of VISA mode signal to VGA channel, enter factory menu of Auto Color Setting item,
select VGA and press enter to do Auto Color.
3.6 YPbPr Auto Color
Input a high definition signal of VG-848, enter factory menu of Auto Color Setting item, select YPbPr
and press enter to do Auto Color.
3.7 AV Auto Color
Input FLUKE VIDEO signal of PAL, select PATTERN of 100% Color bar, enter factory menu of Auto
Color Setting item, select VIDEO1 and press enter to do Auto Color.
3.8 SCART Auto Color
Connect SCART1 RGB signal, input FLUKE signal of PAL system, PATTERN of 100% Color bar,
enter factory menu of Auto Color Setting item, select SCART1 and press enter to do Auto Color.
4 Performance check
4.1 TV function
Connect RF-TV terminal to the central signal source, enter the search menu auto search, check if
there is station skipping, manual search, fine tuning, the output of earphone and speaker, the
picture are normal.
4.2 SCART/AV/S terminal
Input SCART1(RGB+CVBS)/SCART2(CVBS+YC)/AV/S signal, check if the picture and sound are
normal.
4.3 AUDIO OUT/VIDEO OUT terminal
Separate input signal at the status of TV/SCART/AV/S, connect AUDIO/VIDEO OUT to the monitor
and check if the sound and the picture of the AUDIO OUT are normal.
4.4 SCART terminal
4.4.1 check the content of SCART OUTPUT
Separate input signal at the status of TV/SCART/AV/S, connect AUDIO/VIDEO OUT to the monitor,
check if the picture and sound of SCART1 OUTPUT are the picture and sound of TV when input
SCART1(RGB+CVBS) and check if they are normal; check if the picture and sound of SCART2
OUTPUT are the picture and sound of the present signal when input SCART2(CVBS+YC) and
check if they are normal.
4.4.2 check the function of SCART INPUT
a) Connect SCART1 and the signal generator after turn on, the TV should auto switch to SCART1
RGB or SCART1 CVBS. Connect SCART2 and the signal generator after turn on, the TV should
auto switch to SCART2 CVBS or SCART2 YC.
b) SCART signal generator sends CVBS signal (color bar and multi-burst) to SCART1, check if the
picture is normal, the OSD should be SCART1 VIDEO; the OSD should be SCART1 RGB when
SCART1 signal switches to RGB format.
c) SCART signal generator sends CVBS signal (color bar and multi-burst) to SCART2, check if the
picture is normal, the OSD should be SCART2 VIDEO; the OSD should be SCART2 S-VIDEO
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when SCART2 signal switches to YC format.
d) Disconnect SCART signal, the unit should return to the present TV situation.
Note: the function is act except VGA, YPBPR, HDMI.
4.5 VGA terminal
Input VGA signal (VG-848 signal generator), separate input VGA format signal of table 1 and check
if the picture and sound are normal after auto correction. If the image is interfered, press the auto
adjust button on the remote control again and check if it is normal.
Table 1 VGA signal format
Picture element
No Resolution H-SYNC(kHz) V-SYNC(Hz) Remark
clock (MHz)
1 640X480 @ 60 885 25.175 31.47 59.94
2 640X480 @ 72 851 31.500 37.86 85.08
3 640X480 @ 75 852 31.500 37.50 75.00
4 640X480 @ 85 334 43.500 43.269 85.00 7253
5 720X400 @ 70 877 28.320 31.47 70.08
6 720X400 @ 85 960 35.500 37.93 85.04
7 800X600 @ 56 853 36.000 35.16 56.25
8 800X600 @ 60 854 40.000 37.88 60.32
9 800X600 @ 72 887 50.000 48.08 59.80
10 800X600 @ 75 945 49.500 49.88 75.00
11 1024X768 @ 60 856 65.000 48.36 60.00
12 1024X768 @ 70 857 75.000 56.48 70.07
13 1024X768 @ 75 858 78.750 60.02 75.03
14 1280X1024 @ 60 963 108.000 63.98 60.02
15 1280X1024 @ 75 859 135.000 79.98 75.02
16 1600X1200 @ 60 859 162.000 75.00 60.00
4.6 YPBPR terminal
Input YPBPR signal (VG848 signal generator), separate input YPBPR format signal of table2 and
check if the picture and sound are normal.
Table 2 YPBPR signal format
No Resolution Mode VG848 timing Remark
1 712X484 @60Hz 480i 968
2 720X4843@60Hz 480P 978
3 702X574 @50Hz 576i 969
4 756X557 @50Hz 576P 979
5 1280X720@50Hz 720P 50 5 SET
6 1280X720@60Hz 720P 60 976
7 1920X1080@50Hz 1080i 50 1 SET
8 1920X1080@60Hz 1080i 60 972
9 1920X1080@50Hz 1080P 50
10 1920X1080@60Hz 1080P 60 970
6
4.7 HDMI terminal
Input HDMI signal (VG848 signal generator), separate input YPBPR format signal of table1 and
table2 and check if the picture and sound are normal.
Check the picture and sound by using VG849 with HDMI terminal.
4.8 DVT-T function check
Connect DVB-T RF terminal to the central signal source, enter the search menu auto search,
check if it can search the program or there is station skipping, check the output of earphone and
speaker, if the picture are normal. Attenuate the signal to 25dBuV(16QAM program) and check the
picture and sound.
4.9 Ex-factory preset
Perform "factory reset" of MENU to do ex-factory preset.
5.10 Packing
Check the accessories and pack them in box.
Method of software upgrading
The FY# series models enable you to update software through the serial interface.
Hardware requirements: 1. One serial cable with female end and female end;
2. One PC set;
Steps of software updating are as follows:
1. Install Gprobe 5.0:
The first: Double click the GProbe5[1].0.0.15_S0006-EXE-09A to install it:
According to the prompt of Windows and follow the steps one by one to finish the installation.
The second: Double click the GPorbe5[1].0.0.15Update1_S0006-EXE-10A to install it:
According to the prompt of Windows and follow the steps one by one to finish the installation.
2. Copy the full directory of Isp_fastflash to anywhere
E.g. take the root directory of C:\ as an example for the following explanation:
Copy the updating file *.hex to the directory of C:\ Isp_fastflash\
E.g. C:\ Isp_fastflash\20Y25.hex.
3. Open C:\ Isp_fastflash\Isp_parallel\ bat.txt as follows:
7
Properly set the path of RAMWrite "C:\isp_fastflash\Isp_parallel\TEMP_OBJECT\isptemp_ parallel.hex"
and FastFlashWrite "C:\isp_fastflash\20y25.hex", save them and close.
4. Set the LCD to off. Connect the Y# updating board and PC with parallel cable.
5. Connect the VGA MONITOR interface on the Y# updating board with the VGA cable, connect the
other end to the VGA interface of the LCD.
6. Turn on the LCD
Double click to run Gprobe5:
8
Click the icon of :
Set the Device to Parallel.
Then click the item of Delays and Buffer Size:
9
Set Long to 50000 ms.
Click the item of Parallel:
Set Clock to 120000 Hz
10
7. Click Batch,
Select the path of the File: bat.txt
Select bat.txt and click to open it:
Click "OK" to start the process of burning the program.
11
The following screen appears when the process if finished.
If you want to update the software next time, you just need to click the pull-down menu to select the
desired Batch file and execute it in the following screen.
12
Note: Do not cut off the power or turn off the unit during the burning process, or the flash may be
damaged.
Check the following if you fail to update:
1. Check whether all cables are properly connected. If LCD is turn on.
2. Check the settings of Gprobe.
3. It is wrong if the Gprobe shows as the following icon.
Now just click the icon of to show below icon.
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Block diagram
14
Working principle analysis of the unit
The unit has two modules: video module and sound module. The diagram is show as fig 1 and fig 2:
Pre-IF
IF IC
SAW
Fig1 diagram of video module
Fig2 diagram of sound module
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1. Video module
There are three kinds of terminal of SCALER FLI8548:
A: 16 channel analog signal input
B: one group 24BIT digital signal input
C: one group HDMI digital signal input
SCART1, SCART2, AV, DVB-T, TV input from terminal A;
VGA, YPBPR via switch PI5V330 to ADC CAT9983, after CAT9983 processing output 24BIT
DIGITAL DATA to terminal B;
HDMI1 and HDMI2 via FSHDMI04 switch directly to terminal C.
SCALER FLI8548 has only three ADC of 10BIT(16-rout analog signal via internal MUX switch to
three ADC), so the signals(SCART1, SCART2, AV, DVB-T, TV) input to terminal A can't cooperate to
perform PIP each other. The function of PIP can only realize by the signals input from the three
terminals(A, B and C).
All the signals via FLI8548 processing to the panel directly, the output interface is configurable for
single wide TTL, LVDS(18,24 or 30-bit RGB) or dual wide TTL(18, 24-bit RGB), LVDS(18. 24 or
30-bit RGB). FY# use the dual wide LVDS(30-bit RGB) to support the 1080P panel.
2. TV module
RF signal via the tuner to output 38.9MHz(L) or 33.5MHz(L') IF signal, via pre-IF circuit and two
SAW to amplify and separate VIF and SIF, then it sent to IF decode IC TDA4470. VIDEO-OUT from
TDA4470 via switch HEF4052T select and four filters, output CVBS to FLI8548 image processing.
SIF from TDA4471 sent to sound processing IC N03SGTV5830.
Diagram of TDA4470 is below:
16
17
3. Sound module SGTV5830 Multistandard TV Audio Processor
The diagram is below:
18
Input pins:
AIN3: AV L/R input AIN4: SCART2 L/R input
AIN5: SCART1 L/R input AIN6: DVB L/R input
AIN8: YPBPR L/R input AIN9: VGA L/R input
I2SAIN: I2S input SIF1: SIF input
SIF is directly sent to SGTV5830 ADC and sound demodulate module (stereo identify), then output
to SSS(SOURCE SELECT SWITCH) to output selection.
L/R of VGA, YPBPR, AV, DVB-T, SCART1 and SCART2 will be sent to SGTV5830 analog input
switcher to output to ADC, then to SSS(SOURCE SELECT SWITCH) to output selection.
Output pins:
MAIN-OUT: MAIN-OUT
HP-OUT: TV-OUT
AOUT0: HP
AOUT1:AV-OUT
AOUT2: SCART1-MONITOR OUT
I2SA-OUT: I2S OUTPUT
All of the sound signal via front-processor to SSS switch, the sound of main channel will output
I2S-OUT to FLI8548 as a signal of SYNC DELAY, then sent back to SSS switch to SGTV5830
digital processing module(DAP), after processing back to SSS switch output.
Note:
a) The reason why AOUT0 act as HP OUT while HP-OUT act as TV-OUT is that when two
channels(two of AV, SCART1, SCART2, DVB, YPBPR and VGA) perform PIP, the main picture
19
via ADC and SSS switcher output MAIN-OUT. There is only one channel ADC, the signal can't
go through another channel HP. When AOUT0 act as HP OUT, it can use "Analog Input Switch"
switch the sound of PIP to AOUT0 and use the earphone sound amplifier to control the volume.
b) The reason why output to FLI8548 a signal of SYNC DELAY is that when process the picture
and sound at the same time, the process of image is much more complex and needs more time,
so they may no-sync. When HDMI act as the main picture and occupy the I2S terminal, SYNC
DELAY is needless.
SGVT5830 output MAIN L/R to sound amplifier MPS7722, then to speaker.
4. Audio amplifier MPS7722
The MPS7722 is a dual ended 20W Class D Audio Amplifier with +24V power supply. It has the
capability of delivering 2X12/20W into 6 bass speakers and 1X 6/12W treble speaker.
20
21
Gain (V/V) Gain (dB) RFB (K) RIN (K) CINT FSW VDD (V) Remark
17.4 24.8 82 4.7 5.6nF 720KHz 24 FY#
3.9 15.0 39 10 6.8nF 660KHz 12 MPS7722
8.2 18.3 82 10 3.3nF 660KHz 12 MPS7722
8.3 21.5 39 4.7 6.8nF 660KHz 12 MPS7722
17.4 24.8 82 4.7 3.3nF 660KHz 12 MPS7722
5.6 15.0 56 10 8.2nF 670KHz 24 MPS7722
8.2 18.3 82 10 5.6nF 720KHz 24 MPS7722
11.9 21.5 56 4.7 8.2nF 670KHz 24 MPS7722
17.4 24.8 82 4.7 5.6nF 720KHz 24 MPS7722
33.0 30.4 330 10 1.8nF 700KHz 24 MPS7722
5. NJW1109
IN a,b: HP L/R
SCL,SDA: SCL_+5V, SDA_+5V
Out A, B: earphone output
V+:+9V power supply
6. High definition module
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VGA and YPBPR via switch PI5V330 to CAT9983 D/A convert. CAT9983 has a 150M band
width, three groups ADC with 8-bit MICROVISON, support YPBPR 1080P input.
CAT9983
Note: pin COAST and CLAMP connected to ground for auto test.
23
7. Digital HDMI module
Two groups HDMI via video switch IC FSHDMI04 to HDMI input port of FLI8548, which
integrated HDMI reception and support digital 1080P input.
FSHDMI04(with ESD) diagram is below:
8. FLI8545 system module
Feature:
3D comb filter, support multi-system TV signal and MICROVISION
Integrated triple 10-bit ADC.
HDMI receiver, support 1080P input, I2S output
Built-in MCU, GPIP control
ACC(Adaptive Contrast and Color), ACM(Active Color Management), DCDI(Dynamic
mode test).
24
25
9. Other
Power control
The unit adopts a PHILP power control IC, which works at standby and the power
consumption below 1W, it also realizes the on time turn off/on.
26
DDR MEEORY
The unit adopts 2 chips 16M*16bit DDR SGRAM of 200M speed, 32-bit of data and 12 bit of
address.
FLASH and EEPROM
1M*16-bit of FLASH and 64K bit of EEPROM
10. DAP module (include AVC, SRS, TONE CONTROL, EQ ect,.)
11. Power part
backlight
isolation audio amplifier
Rectify
isolation
isolation
Working principle of power:
The input AC power via EMC filter and rectification circuit, it sent to PFC(power factor correct L6563)
to output DC400V, which will be separated into two ways, one way via standby circuit (isolation D/D
convert FSDH321) output 5VAND 32V; another way via semi-bridge circuit(TEA1610T) output 24V,
18V, ect. At standby, power board send out Vsb(3.3V) to cut off 5VSC, 32VSC output by the control
of Standby signal and stop working of PFC circuit(L6563) and semi-bridge (TEA1610T). When turn
on, it makes all the IC working and output voltage.
L1653:PFC( power factor correct)
TEA1610T: Isolation D/D convert (400VDC converted to DC 24V, 18V, ect.)
FSDH321: Isolation D/D convert (400VDC converted to DC 5V, 32V, ect.)
FSDH321 block diagram is bellow:
27
L6563 block diagram is below:
28
29
TEA1610T block diagram is below:
30
31
panel
backlight backlight
Wiring diagram
panel
backlight time sequence control
panel
power supply of main board
board
power supply power supply of audio amplifier
power supply of TV board to speaker
32
control
TV board
main board
interface board
power switch
upgrade board key board IR receive board
Trouble shooting
Before servicing please check to find the possible causes of the troubles according to the table
below.
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 Possibly due to interference from automobile, train, high
shaped bright spots 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.
There appear streaks or light color Check if interfered by other equipment and if interfered
on the screen possibly by the equipment like transmitting antenna, non
professional radio station and cellular phone.
2.TV set:
Symptoms Possible cause
Unable to switch the power on Check to see if the power plug has been inserted
properly into the socket.
No picture and sound Check to see if the power supply of liquid crystal TV has
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.
Deterioration of color phase or Check if all the picture setups have been corrected.
color tone
Screen position or size is not Check is the screen position and size is correctly set up.
proper
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
crystal TV set and make proper adjustment according to
33
Symptoms Possible cause
the signal types.
Picture too bright and there is Check if the contrast setting is too high.
distortion in the brightest area 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.
Picture is whitish or too bright in Check if the setting for the brightness is too high
the darkest area of the picture Possibly the brightness grade of DVD player
(broadcaster) is set too high.
No picture or signal produced from Check if the cable is disconnected.
the displayer if "XXX in search" Check if it's connected to the proper terminal or if the
appears. input mode is correct.
There appears an indication - Check if the TV set can receive input signal. The signal is
"outside the receivable scope) not correctly identified and VGA format is beyond the
specified scope.
Remote control cannot work Check if the batteries are installed in the reverse order.
properly 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.
No picture and sound, but only Check if the antenna cable is correctly connected, or if it
hash. has received the video signal correctly.
Blur picture Check if the antenna cable is correctly connected.
Of if it has received the right video signal.
No sound Check if the "mute" audio frequency setting is selected.
Check if the sound volume is set to minimum.
Make sure the earphone is not connected.
Check if the cable connection is loose.
When playing VHS picture search When being played or in pause VHS picture search tape
tape, there are lines at the top or sometimes can't provide stable picture, which may lead
bottom of the picture. 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
34
Troubleshooting guide
1. Trouble diagnosis of power
No power
Yes
Check if C539 Check N503
has 5V
No
Check if C533 Yes Check N501 and its periphery (include
has voltage over transformer and the secondary sample
100V feedback circuit.
No
Check the fore
circuit of fuse
and rectifier.
2. No DC output No DC output Check the fore
(Vsb normal) circuit
Yes
Check 32VSC, No Check if Standby No Check the
5VSC is high level correlative circuit
Yes
Check if 24VCF, Yes
Check N504 and
24VSC, 18VSC
the correlative
is normal
circuit
No
Check if the voltage of Yes Check N512 and its periphery
C533 is about (include VCC, transformer
395V(less than 370V is and the secondary sample
abnormal) feedback circuit)
No
Check L6563 and its
periphery (include
the VCC) 35
3. Representative symptoms
(1) no picture, no sound, no raster
Check if the No Check if +3.3V-stby of No Power board no output or
indicator light XB7 9# on main board +3.3V-stby short to the
turns red when is normal ground
power on
Yes IR board has problem.
Yes Indicator light is damaged
If indicator
Check +9V of
light turns blue No No Power board no output or
XB7 1# on main
when turn on +9V short to the ground
board
Yes There is problem
Yes
lie in IR board
Check XB7 Check the power
+5V of 3# and supply of main NB10NS03N404 and
+18V of 5# Yes CPU,DDR(CB47 No their periphery have
-3.3V,CS80-1.8V, problem
C434-2.5V)
No Yes Main CPU NS02, DDR
N400&N402, FLASH
Power board no
NA02 or their periphery
output or +5V, +18V
have problem
short to the ground
36
(2) with sound but no picture
Check if No Check the power No No backlight power supply
backlight is light supply of backlight output or short to the ground
Yes Yes
LVDS power supply XB12 3# switch level is abnormal
of C415 is normal? (such as shortage)
No
N403 and its If X403 has LVDS wave No Main CPU NS02
periphery has output LVDS have problem
problem
Yes
Problem lies in LVDS
wire or panel
(3) with picture but no sound
a) MP7722
If audio amplifier has Speaker damaged
output (if X13 has wave)
No
Audio amplifier and the circuit
If sound processing IC has Yes
has problem. Check the power
output (C116,C117)
supply, 6# MUTE, 14#,19#
No
Sound processing IC N03 and
its periphery has problem
37
b) TPA3001
If audio amplifier
Speaker
output (X12, X13)
No
If sound processing IC Yes Audio amplifier and the circuit has problem.
has output (C27, C29) Check the power supply, 6# MUTE. Turn on
again after power off and check if the audio
No amplifier protection.
Sound processing IC N03 and
its periphery has problem
The output of TPA3001 is differential output, so when check X12, X13 output signal with
oscilloscope, please use the power cord with two pins, otherwise, it may damage the audio
amplifier.
(4) a certain channel abnormal
a) AV no picture
If X09 4# input
signal
Yes No
NS02 or the periphery circuit The path from AV terminal
of AV input have problem to this socket has problem
b) TV no picture
If X09 4# input
signal
Yes No
NS02 or the periphery circuit If N04 12# of TV board has
of TV input have problem output signal
Yes No
N04 emitter-follow circuit TUNER01or the periphery of N04
and N07 has problem has problem. The emphasis is power
supply.
38
c) SCART1 no picture
Check if X203 1#(CVBS) or
3#,4#,5#(RGB) on SCART
board has signal?
Yes No
NS02 or the circuit around The path from SCART1
SCART1 input has problem socket to X203 has problem
d) SCART2
Check if X203 7# on
SCART board has signal?
Yes No
NS02 or the circuit around The path from SCART2
SCART1 input has problem socket to X203 has problem
e) YUV no picture
If RA26 input signal?
Yes No
NA03 and its Check if NA01 5# has
periphery has problem signal
Yes No
The path between YPbPr NA01 or the periphery
socket and NA01 has problem has problem
39
f) D-Sub no picture
If it is normal when
input YPbPr signal
Yes No
If RA20, RA21 input Check follow
sync signal program (e)
Yes No
NA03 and its periphery If NB14 1#, 4# input
has problem sync signal
Yes No
NB14 and its The path between VGA
periphery has problem and NB14 has problem
g) HDMI no picture
If one channel HDMI no Yes The path from NB14 or HDMI
picture socket to NB14 has problem
No
Check if HDCP KEY
flash written.
Yes No
If NB13 pin 28, 30, 33, 35, 38, 40, 43, Write HDCP KEY
45output signal
Yes No
NS02 or the circuit around NB14 or its periphery
HDMI input has problem has problem
40
APPENDIX-A: Main assembly list
Model Part No. Description
L37FY26 667.2FY27-01 Main board
667.2FY27-29 Interface board
667.2FY27-40 Video processing board
667.37FY26-05 Key board
667.37FY26-09 IR receive board
667.42FY26-46 SCART trans-connect board
667.37FT25-20 Power board
301.I42FY27-16A Remote control
335.37022-00 Panel
L42FY26 667.2FY27-01 Main board
667.2FY27-29 Interface board
667.2FY27-40 Video processing board
667.37FY26-05 Key board
667.37FY26-09 IR receive board
667.42FY26-46 SCART trans-connect board
667.42FY27-20 Power board
301.I42FY27-16A Remote control
335.42022-00 Panel
603-L37FY26-10
Ver.1.0