Prima LC-20S3, LC-15S3, LC-20S15, LC-23S18, LC-20S18 Service Manual

LCD TELEVISION

LCD-S# series

Europe

LC-15S3
LC-20S3

LC-20S18
LC-20S15
LC-20S15

LC-23S18

CONTENTS

Safety precautions………………………………………………………………………..…
Alignment instructions …………………………….…….…………………………….…
Method of software upgrading ………………………………………….…….……………
Working principle analysis of the unit……………………………….………….………….
Block diagram…………………………………..……………………………….…………
IC block diagram………………………………………………………………………..……
Wiring diagram ……………………………………………………………………………..
Assembly list……………………………………………………………………………..…
Identification criteria for the bright spot and dark spot of the LCD screen………..….
Troubleshooting…………………………………………………………………………..……
Schematic diagram …………………………………………………………………….…..

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1

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

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

servicing please read the following points carefully.

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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.

3

Alignment instructions

1. Test equipment

PM5518 (Video signal generator)
K-7253 (VGA signal generator)
CA210 (White balancer)

2. The alignment flow chart (see below figure)

Fig.1 Flow process of alignment

Production of main board and TV board on the

line.

Connect to central signal source; check if various

TV functions (station skipping, modulate quantit

y

control etc), check if the output of earphone and

speaker are normal.

ADC correction and white balance adjustment

Input AV/S signal and HDTV signal; check various

functions under AV/S terminal

Check the main board and supply power board

Input YPbPr/YCbCr signal, check the screen display is normal in

the various channel, and various functions (analog quantity

control, line/field center etc.)

Input VGA signal and check if display is normal in

the state of PC and various functions (analog

quantity control, line/field center etc.)

Written N101 and N304

Combined test for general assembly and aging

Check accessories and then packing

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3. Written program

Written program of IC(N101, N304)

4. Main board adjustment

a. According to wiring diagram, connect main board to supply power, the indicator to red.
b. Press the POWER button in the senor control, the indicator to blue
c. Check the picture and sound is normal of TV/SCART/YPBPR/RGB/DVI channel.

4. Aging

a. Install the set
b. Turn on the set, select the TV channel, then let the set no signal in state.

c. Aging one hour.

5. White balance

a. Enter RGB channel
b. Input grid signal(C_Hat_16x12(w)) of 60Hz of VGA terminal, resolution to 640 x 480 of in

optimum resolution. Adjust H-center and V-center, let to the picture normal.
c. Input gray(H)-16 signal, enter the factory menu, select “VGA AUTO COLOR”
d. Exit the factory menu, select the YPBPR/YCBCR channel
e. Input the YPBPR signal, adjust different signal.

f. Input gray(H)-8 signal, using the CA-210 test the third level, adjust brightness and contrast, let

brightness to 180nit, enter factory menu, still the green color temperature value, adjust blue

color temperature and red color temperature, let to x=0.284±0.02, y=0.299±0.02

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 VGA terminal
Input the VGA signal (table 1), and auto correction it, check the picture and sound is normal.

Table1 VGA signal format

Resolution Pixel clock (MHz) H-SYNC (KHz) V-SYNC (Hz)

640x480 @ 60 25.175 31.469 59.900
640x480 @ 75 31.500 37.500 75.000

720x400 @ 70 28.322 31.469 70.086

800x600 @ 60 40.000 37.879 60.317

800x600 @ 75 49.500 46.875 75.000

6.4 YPBPR/YCBCR terminal
Input YPBPR/YCBCR signal(table 2), and auto correction it, check the picture and sound is normal.

Table 2 YPbPr/YCbCr signal format

resolution Pixel clock (MHz) H-SYNC (KHz) V-SYNC (Hz)

1 768x576@50i 14.750 15.625 50
2 776x482@60i 15.734 15.734 60

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3 720x480@60p 27.027 31.500 60
4 720x576@50p 27.000 31.250 50

5 1280x720@60p 74.250 45.000 60
6 1920x1080@50i 74.250 28.125 50
7 1920x1080@60i 74.250 33.750 60

6.5 For factory preset, see table. 3

Table 3 Factory Preset

Item Factory Preset Item Factory Preset

Picture mode NATURE OSD language English

Sound mode User Color temperature Standard

Volume 30

Backlight 50

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Method of software upgrading

Steps of software upgrading are as follows:

1. Using the parallel port wire and DVI transfer to VGA connection wire and then connect them by a
upgrade board.

2. Enter the factory menu, select upgrading item.

3. Connect main board to PC

4. Operation the vct49xyi_start.exe

display the software interface follow as:

5. Click the “TVT” item:

6. Click the BOOTLOADER button, display the DOS interface, after the interface disappear, click

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the BOOTLAODER VERSION, if it value form 0 to 21, connecting is normal.

7. Click the ERASE 16 BIT FLASH, erasure the program. Click the BOOTLAODER VERSION, if it
value form 21 to 1, the program is erasure.

8. After erasure the program, click the black bar,

then display the interface, select the upgrading program.

After select the program, press the OK button, return the menu, click LOAD BIN-----FLASH, after
the written the program is finish, the BAR disappear.

9. Turn off the power supply, return the set is over.
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.