Xoceco LC20H15 Schematic

LCD TELEVISION

LC20H15

CONTENT

Safety instructions………………………………………………………………………..… Instructions on adjusting and testing…………………………….…….………………… Trouble shooting……………………………………………………….…………………… Method of software upgrading………………………………………….………………… Briefing on LC20H15 and its working principle………………………………..………….

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

Serial NO. of parts……………………………………………………………………….… Identification criteria for the bright spot and dark spot of the LCD screen………..…. Troubleshooting guide………………………………………………………………..…… Exploded views…………………………………………………………………………..… Schematic diagram…………………………………………………………………….…..

1 3 5 7 9 18 19 19 20 22 24

No sound (with TV input as an example)

Attention: This service manual is only for service personnel to take reference with. Before servicing please read the following points carefully.

Safety instructions

1. Instructions

1.1 Be sure to switch off the power supply before replacing or welding any components or inserting/plugging in connection wire

1.2 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.

1.3 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 eq uipment and devices or expo sure to sunlight etc.

Otherwise bad effect will result.

2.5. If any foreign substanc e such as water, liquid, metal slices or other matt ers happe ns t o 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 scre en 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 w ire when the module i s in operat ion or just after t he 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 befor e t he pulling out or plugging in t he 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 T V set is comp osed of CMOS i ntegrate d circuits, it’s neces sary 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 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

0----+50 C

operation

Scope for

-20----+60 C

storage

humidity Scope for

20%---85%

operation

Scope for

10%---90%

storage

2.13. Display of a fixed picture for a lon g time may result in ap pear ance of p ictur e residue on t he screen,

as commmonly called “ghost shadow”. The extent of the residual picture varies with the maker of

LCD screen. This phenon menon does n’t repre sent failure. This “ghost shadow ” may remain in t he

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 v iew ing 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 calibration See fig.1.

Production of main board and TV board in the

Connect the central signal source and check if the functions of TV (Station missing, syste identification ,analog control etc.), and the output o

Input AV/S signal and check for various functions

3 Flash writing programs Flash write memory U 4 Adjustment and calibration for the main board

a） Connect the main board X501 to infrared receiving board (as per wiring diagram

b)Connect PC, upgrade the program of FLASH U13, push the POWER key on the remote control

c) About 4 minutes later the indication lamp of the infrared receiving board turns blue. Measure U2

PIN2 to be 3.3 V, measure U4 PIN2 to be 1.8 V,and measure U5 PIN2 to be 1.8 V.

d) Flash write DDC program.

Flash memor y U13 U3 N301 N303

production line

Check the main board

Check TV board

Functional adjustment for general assembly

in the case of AV/S terminal

Input YprPb signal and see if the display is normal

Input VGA signal and see if the displ ay is normal under PC status and check for various functions (analog control), l ine/field centerect.

Check if the AV OUT function is normal separately in the status of input separately in th status of input TV/S terminal/Av signal, and if

Fig.1 Adjustment and

rocess

U3 N

calibration

1 N2

203-L20H80-01JL) and insert the plug of power supply adapter (FSP060-1AD103) into X101. Now the indication lamp of the infrared receiving board is red.

set. Now the indication lamp of the infrared receiving board is out.

Check accessories，packing

under PC status and check for various functions (analog control), line/field center etc.

5 Adjustment and calibration for the TV board Connect the main board X 501 to infrared receiving board (as per wiring diagra m 2 03-L20H80-01JL)

and press the POWER key on the remote control set. Now Now the indication lamp of the infrared receiving board is blue. Measure N3 PIN2 of TV board to be 3.3 V, one terminal of inductor L107 to be 5 V and one terminal of inductor L4 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 “four grade gray”(Gray(H)-4 ). Use CA-210 to measure the third grade and adjust

the brightness and contrast so that Y is around 150. 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 640x480 @75Hz “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 perf orm “calibration of

ADC”.

i） Exit from the factory menu, input the signal of “four grade gray” (Gray(H)-4 ) and enter the user

menu. Adjust the brightness and contrast. Use CA-210 to measure the third grade so that Y is around 200. Enter the factory menu and adjust the green color temperature and blue color temperature so that x=270,y=283(red color temperature is constant as128).

j） Enter TV mode and adjust channel No. Enter “D8”signal and adjust the color to 0. Adjust the

brightness and contrast. Use CA-210 to measure the third grade so that Y is around 200.

k） Enter the factory menu and adjust the green color temperature and blue color temperature so

that x=270,y=283(red color temperature is fixed as128). 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. 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 pic ture and sou nd fro m AV OUT is n or mal. (Not e: In t he st atus o f S t er mina l,

the output picture from AV OUT is colorless.) d) VGA Interface

Input VGA signal(K7253 signal generator). Separately input the four types of VGA format 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 1 Display Format of PC

Item

1 640 x 480 @ 60 25.175 31.469 59.900 2 720 x 400 @ 70 28.322 31.469 70.086 3 800 x 600 @ 60 40.000 37.879 60.317 5 1024 x 768 @ 60 65.000 48.363 60.004

Resolution

Picture

element clock

(MHz)

H-SYNC

(kHz)

V-SYNC

(Hz)

Remark

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/50 Hz,480I/60 Hz

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 wav e reflect ed from hillt op or building.

Picture is interfered by stripe

shaped bright spots

There appear streaks or light color on the screen

 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.

 Check if interfered by other equipment and if interfered

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 po wer supply of liquid cr ystal T V ha s been

switched on. (as ca n be indic ated by th e red LED at the front of the TV set)

 See if it’s receiving the sig nal that is transmitted f rom 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 cab le co nnec ti on b et we en vid eo f r equency

source and the liquid crystal TV set is correct. Deterioration of color phas e or c olor 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”setti ngs of the liqui d c r ystal

Picture too bright and there is distortion in the brightest area

Picture is whitish or too bri ght in the

darkest area of the picture

No picture or signa l 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.

 Check if all the picture setups have been corrected.

TV set and m ake proper adjus tment according to the signal types.

 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 se t can receive inpu t signal. T he signa l 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 obstr uct bet ween the rem ote contr ol 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 i f it 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 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 upgr adi ng

Steps of soft w are 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 t o 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 pr ogr am:

Based on the computer features, set up the serial port(COM Port). Select corresponding serial port

(if it’s unable to FLAS H WRITE, change t o another port) . Baud is se lected to be 115200. Then select Reset 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 t o 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.

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