XOCECO LC20H3D User manual

COLOR TELEVISION
LC20H3D

CONTENT
Safety instructions………………………………………………………………………..…
Instructions on adjusting and testing…………………………….…….…………………
Trouble shooting……………………………………………………….……………………
Method of software upgrading………………………………………….…………………
Brief introduction and working principle of L20H3………………………………..………….
Wiring diagram……………………………………………………………..……………....
Serial NO. of parts……………………………………………………………………….…
Identification criteria for the bright spot and dark spot of the LCD screen………..….
Troubleshooting guide………………………………………………………………..……
Exploded view…………………………………………………………………….…..........
1
2
6
8
9
19
20
20
21
23
Part list................................................................................................................. 25
Schematic diagram...............................................................................................43

1
Safety instructions
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.
2.9As 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 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
A
ttention: This service manual is only for service personnel to take reference with. Before servicing
please read the following points carefully.

2
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 C
Scope for storage -20----+60 C
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 commmonly called “ghost shadow”. The extent of the residual picture varies with the maker of
LCD screen. This phenonmenon 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.Wheng installing it please make sure to put it in place.
3.2. For service or instatallation 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.
Instructions on adjusting and testing
1.Adjusting and calibrating equipment
Digital multi-meter (or oscilloscope)
5515 signal generator
5518 signal generator
PC set(FLASH writing programs have to be installed first.)
K7253(VGA, YprPb signal generator)
CA210 (LCD white balancer)
DVD broadcaster
2.Flow chart for the adjustment and calibrationSee fig.1.
Check if N4, N20, N303, N302 has
been FLASH written.
Produce main board, TV board on line

3
Figure 1. Flow process of adjustment and calibration
3.Flash writing programs
Flash write memory N4, N20, N303, N302
4.Adjustment and calibration for the main board
a)Connect the main board X501 to infrared receiving board (as per wiring diagram
203-L15H30-01JL) and insert the plug of power supply adapter (FSP048-1AD101C for15”,
FSP060-1AD103 for 17”, 20”) into X1. Now the indication lamp of the infrared receiving board is red.
b)Connect PC, upgrade the program of FLASH N20, push the POWER key on the remote control
set. Now the indication lamp of the infrared receiving board is out.
c) About 4 minutes later the indication lamp of the infrared receiving board turns blue or yellow.
Measure L102 PIN2 to be5.0 V, measure L107 PIN2 to be 3.3 V.
d) Flash write DDC program.
Input YprPb signal, check if the display is normal unde
r
PC and various functions (analog quantity control,
line/field center etc.)
Check accessories and then packing
Check main board
Check TV board
Combined test for general assembly
Connect to central signal source satellite signal, check if various TV
functions (station skipping, modulate quantity control etc), check if the
output of earphone and speaker are normal
InputAV/S terminal signal, check
different functions of AV/S terminals
Adjust TV board
Input VGAsignal and check if display is normal in
the state of PC and various functions (analog
quantity control, line/field center etc.)

4
5.Adjustment for the TV board
Connect the main board and infrared receiving board (as per wiring diagram 203-L15H30-01JL) and
press the POWER key on the remote control set. Now the indication lamp of the infrared receiving board
is blue or yellow. Measure N301 PIN2 of TV board to be 3.3 V, one terminal of inductor L630 to be 5 V
and one terminal of inductor L632 to be 12 V
6.Adjustment of white balance (using the white balancer CA210 and K7253 signal generator specialized
for LCD)
a).Install the whole TV set
b).Enter the factory menu and perform”PW1306 reset”
c).Exit from the factory menu. Press “signal source” key and enter YPbPr .
d).Input YpbPr signal: 640x480p 60Hz (K7253).
e).Enter the user menu. Set the brightness to 50 and contrast to 50. Press “factory” key to enter the
factory menu, perform “ADC calibration”, input signals of “black field”(EMPT),”white
field”(White-(100%))”fully red”(Full_Magenta)respectively and then calibrate three times.
f).Input signal of “eight grade gray”(Gray(H)-8 ). Use CA-210 to measure the sixth grade and adjust
the brightness and contrast so that Y is around 180. Enter factory menu and adjust the green color
temperature and blue color temperature so that x=270,y=283(red color temperature is constant as128).
g).Exit from the factory menu and enter route RGB. Input 60Hz “pane signal ” (C_Hat_16x12(W))
through port VGA. Enter the user menu and adjust the brightness to 50 and contrast to 50. Adjust the
line center and the field center so that the picture is correctly positioned.
h).Input signal of “16 gray grades” (Gray(H)-16). Enter the factory menu and perform “calibration of
ADC”.
i).Exit from the factory menu, input the signal of “eight grade gray” (Gray(H)-8 )and enter the user
menu. Adjust the brightness and contrast. Use CA-210 to measure the sixth grade so that Y is around
180. Enter the factory menu and adjust the green color temperature and blue color temperature so that
x=284,y=299(red color temperature is constant as128).
j).Enter the factory menu and adjust the green color temperature and blue color temperature so that
x=284,y=299.
Notice: For the best discrimination rate of LCD screen, see table 1.
Table 1:LCD resolution of best
Screen size Factory LCD resolution of best
Samsung
AU
Sanyo
15”
CPT
1024x768
Samsung
17” AU 1280x1024
AU 800x600
Chimei
20” LG 640x480
7.Performance check
a).TV Interfaces
Connect RF port to central signal source. Enter station search menu - auto station search. After
system adjustment is over, check if there is any station missing and then check semi-auto station search.

5
Check if fine tuning is normal.
Check if the output of earphone or loudspeaker is normal and if the picture is normal.
b).Interface of AV/S Terminals
Connect to access the signal of AV/S terminals separately and check if the picture or sound is
normal.
c).AV OUT Termianl
Input the signals separately in the status of TV/AV/S terminal. Connect AV OUT terminal to monitor
and check if the output picture and sound from AV OUT is normal. (Note: In the status of S terminal, the
output picture fromAV OUT is colorless.)
d).VGA Interface
Input VGAsignal(K7253 signal generator). Separately input the four types of VGAformat signals as
listed in Table 1. Wait till auto calibration is over. Then check if the picture and sound is normal. If there
has been interference to the picture then press the auto set key on the remote control once again and
check if the display is normal. Table 2.VGA format signal
screen size resolution Image clock(MHz) H-SYNC(kHz) V-SYNC(Hz) remark
640x480 @ 60 25.175 31.469 59.900
720x400 @ 70 28.322 31.469 70.086
800x600 @ 60 40.000 37.879 60.317
1024x768 @ 60 65.000 48.363 60.004
640x480 @ 75 31.500 37.500 75.000
800x600 @ 75 49.500 46.875 75.000
15”
1024x768 @ 75 78.750 60.023 75.029
640x480 @ 60 25.175 31.469 59.900
720x400 @ 70 28.322 31.469 70.086
800x600 @ 60 40.000 37.879 60.317
1024x768 @ 60 65.000 48.363 60.004
640x480 @ 75 31.500 37.500 75.000
800x600 @ 75 49.500 46.875 75.000
1024x768 @ 75 78.750 60.023 75.029
1280x1024@60 108 63.981 60.2
17”
1280x1024@75 135 79.976 75.025
640x480 @ 60 25.175 31.469 59.900
720x400 @ 70 28.322 31.469 70.086
800x600 @ 60 40.000 37.879 60.317
640x480 @ 75 31.500 37.500 75.000 CMOscreen
nonsupport
20”
800x600 @ 75 49.500 46.875 75.000 CMOscreen
nonsupport
e). YprPb Interface
Connect to access YprPb signal(K7253 signal generator). Separately input the five types of YprPb
format signals -- 480P/50 Hz,480P/60 Hz,720P/60 Hz,1080I/50 Hz,1080I/60 Hz and check if the picture
and sound is normal after auto calibration is over.
Connect to access YprPb signal(DVD signal generator). Input the signals -- 480I/50Hz,480I/60 Hz

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separately and check if the picture and sound is normal.
8.Preset ex-works
In the status of TV enter the factory menu by pushing the factory key and then perform presetting.
9.Ex-works packing
Check accessories and then pack them in box.
Trouble shooting
Before servicing please check to find the possible causes of the troubles according to the table below.
1.Antenna:
Picture is out of focus or jumping Bad status in signal receiving
Maybe broadcast signal itself is not good
Check if the outdoor antenna is disconnected.
Check if the antenna is correctly oriented.
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 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.
There appear streaks or light color
on the screen Check if interfered by other equipment and if interfered possibly by the equipment like transmitting antenna, non professional radio
station and cellular phone.

7
2.TV set:
No picture and sound, but only
hash. Check if the antenna cable is correctly connected, or if it has received the video signal correctly.
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
color tone Check if all the picture setups have been corrected.
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 crystal
TV set and make proper adjustment according to the signal
types.
Picture too bright and there is
distortion in the brightest area 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.
Picture is whitish or too bright in
the darkest area of the picture Check if the setting for the brightness is too high Possibly the brightness grade of DVD player(broadcaster)is set
too high.
No picture or signal produced from
the displayer if “XXX in
search”appears.
Check if the cable is disconnected.
Check if it’s connected to the proper terminal or if the input
mode is correct.
There appears an indication -
“outside the receivable scope) Check if the TV set can receive input signal. The signal is not correctly identified and VGA format is beyond the specified
scope.
Remote control cannot work
properly 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.

8
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
tape, there are lines at the top or
bottom of the picture.
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 TVIn 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
Method of software upgrading
Steps of software upgrading are as follows:
1.Select a serial connection wire and a VGA connection wire and then connect them by means of a
patch panel;
2.Use a serial wire to connect the PC to the patch panel and set TV set to off state;
3.Open the software upgrade file holder and double click
FlashUpgraderNT(use under window 2000/XP/NT)
FlashUpgrader(use under window 98),
The following interfaces will show up after running the program:
Based on the computer features, set up the serial port(COM Port). Select corresponding serial port (if it’s
unable to FLASH WRITE, change to another port). Baud is selected to be 115200. Then select Reset

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Target After Download. Click FLASH pushbutton, it’s ready to run. For other settings, please refer to the
Fig.Above (already defaulted by the system, normally no need to change).
4.Switch on TV set the FLASH write program begins to run;
5.After FLASH write is over, push button “cancel” will become flash. Then shut the main power supply
and it’s OK just switch it on again.
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.
Brief introduction and working principle of L20H3
LC20H3 multi-media liquid crystal TV broadcast and receiving set adopts liquid crystal display
screen of LG 20.1, which is provided with NTSC color system receiving function in addition to AV
input,S-VHS input,high definition signal port for component YPrPb/YcbCr,PC VGA port, earphone output
and other signal ports. For power supply an externally connected power adaptor is provided.
The circuitryof LC20H3is composed of RFmodule board, video signal board, digital signal picture
processor and AC-DC transformer, and DC-DC circuit board.
The working process is as follows. The radio frequency signal undergoes an integrated tuner
TUNER1 before a color full video signal is generated. This video signal then enters analog board
decoder IC N303 VCT3833 Pin19 where it is processed and it’s output as analog signals R, G, B through
Pin42, PIN43, PIN44. Audio frequency signal is processed with sound in IC N401 MSP3420G and then
output through MSP3420G Pin28 , Pin27 to SRS for surround sound processing in IC N403 M62494E.
Finally it is subject to power amplification in IC N404 TDA1517 before it is output to speaker.
VGA signal/high definition signal is input to personal computer through the main board. The signal
selected by Y/Pb/Pr through 5 way 1/2 switches IC(N1 BA7657F)is subject to reselection together with
signal TVRAIN, TVGAIN, TVBAIN through 5 way 1/2 switches IC(N5 BA7657F). Finally signals R, G, B
are selected and sent to the main processing chip IC N19 PW1306.
IC N19 PW1306 is a built-in X86 CPU of the main processing IC,externally connected by 8M
Flash(N20) memory to control the whole system. The input signal of V-port and G-port is subject to
internal arithmetic processing and then output as R, G, B signals with electric level of 24 bit TTL to
sockets JP3 and JP4, where through connection wires the signals are sent to the port of LG liquid crystal
screen and for the realization of picture reproduction.

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BLOCK DIAGRAM

IC BLOCK
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
1
2
1
2
1
2
1
2
12
DET
Logic
Syncsepa
Ground
Ground
Ground
Ground
VCC
CTL (H: IN1, L: IN2)
Red 1 input
Green 1 input
Blue 1 input
Red 2 input
Green 2 input
Blue 2 input
VD 1 input VD 2 input
VD output
Blue output
Composite sync output
Composite video input (Sync on Green)
Green output
Red output
HD output
HD 2 input
HD 1 input
HD Sync signal detector
BA7657F / BA7657S

PW130
Figure 1-1 ImageProcessor Block Diagram
A/ D
R G B
Clamp
Color
Space
Converter
CLK RGB
HS,VS
Dat a MUX
Auto Image
Optimization
DRGB (23:0) DGRGB(23:0) DVS, DHS, DEN, DCLK
NMI
Interrupt
Controller
RxDTxD
UART
Watchdog and
Timer s
Processor ROM/
RAM Interface
JTAG Debugger
16-Bit
Microprocessor
PortA(7:0)
GPIO PWM IR
Decoder
A
(19:1)
D
(15:0)
CS
(1:0)
2-Wire
Serial
Microprocessor Bus
Memory Out Bus
Memory
Buffer
Processor
Memory
Interface
Memory In Bus
OSD
VYUV(7:0)
VCLK
VPEN
PW130 ImageProcessor
Internal Block Diagram
ADC
VIDEO
PORTD (7:0)
Sync
Processing
HSHSYNC,
VSYNC
SOG
Stripper
SOGIN
FILT PLL CLK
RAI N GAI N BAI N
A/ DClamp A/ DClamp
VS
PowerOn
Reset
RESET
Reset
XI XO
PLL and
Oscillator
MCL K DCLK UCLK
Scaler Color
Matrix
OSD
and
Gain
Color
Lookup
Ta bl e s
Display
Ti m i ng
Generator
Color
Space
Expander

TDA4470
Block Diagram
ÏÏ
Ï
ÏÏ
ÏÏ
ÏÏ
ÏÏ
AGC
(VIF)
Tuner
AGC
ÏÏ
ÏÏ
ÏÏ
Ï
ÏÏ
ÏÏ
ÏÏ
AGC
(SIF)
Ï
Ï
Ï
Ï
Ï
Ï
Ï
11
10
Tuner
Ï
Ï
Ï
Ï
Ï
Ï
Ï
Ï
27
28
3
1
2
Ï
Ï
5
SIF 2
SIF 1
VCO
+
phase shift
AFC
Standard
Supply
ÏÏ
ÏÏ
ÏÏ
L’ switch
VCO
21
20
18
Loop
filter
14
Ï
Offset
comp.
(optional)
26
FPLL 0°
90°
VIF amp
6
7
8
15
VIF
CAGC
CBL
Take over
point
SIF input
switch
CAGC
22
12
4,9,16
13 Standard
switch
23 VS
Ï
Ï
17
CRef
Intercarrier
(FM / NICAM)
24
FM det.
AM det.
SIF amp
25 AF
(AM)
AFC
Video
95 10851
Ï
Video det.
Control
ÏÏ
ÏÏ
19 AFC
switch
Ï
Ï
ÏÏ
Figure 1. Block diagram