changhong global LS03 Service Manual

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LCD TELEVISION

SERVICE MANUAL

CHASSIS LS03（U）

Please read this manual carefully before service.

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CONTENTS

PartⅠ:Specification, feature and Composition ……………………………………3
PartⅡ: Function introduction about the main integrated circuit ………………..6
PartⅢ: Signal Processing Flow chart ….………………………………………….18
PartⅣ: Typical troubleshooting processing flowchart …………………………..21
Annex: Circuit schematic diagram

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PartⅠ: Specification , feature and Composition

Ⅰ. Main feature

1、Radio frequency input
It can receive CATV signal.
2、AV input
Convenient for watching a DVD player,VCR,pickup camera or other playback
devices.
3、S-Video input
Convenient of receiving a high quality component signal from a DVD player.
4、YPbPr input
Capable of receiving the high definition YPbPr signal in 480i, 480P, 576i, 576P, 720P,
1080i formats.
5、VGA input
a. Convenient to connect with a host computer.
b. Use as a data display terminal.
c. Connect the 3.5mm(diameter)audio jack to your computer’s soundcard to listen to
stereo sound transmitted from your home computer.
6、Program & child lock function
Capable of locking any program of the TV and the function button of the front panel.
7、Timer function
8、Blue background with noise reduction
In TV，AV，S-Video，YPbPr and PC modes, screen displays soft blue background ,
if there is no signal input.
9、 Multi Language on-screen display menu
Text and graphical user interface makes the menu operation user-friendly.
10、Power energy Saving mode(power management mode)
When used as PC display terminal without PC signal output, the LCD TV will
automatically power off within 30 Seconds and enter Power Energy Saving Mode. It
will automatically startup again when it receives a signal from the PC.To start the TV
manually with no signal press the number buttons or【 】/【P+】/【P-】 on the remote
control.
11、Plug-and-play
No additional software is needed when the product is used as computer
terminal display.
12、Automatic picture’s quality adjustment
13、No flicker, no radiation, greenness and health
14、Auto on as time is set
15、Zoom mode（for19”,22”Model）
Full-screen 、16:9、cinema、Subtitle
16、Legerity, convenient, low power consumption
17、Picture quality enhancement function
Dynamic skin color correct: improve distort color in picture, make it near to real
color.

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Black level extension: darken the large part of black section to enhance pictures
contrast in the dim background Color edge adjustment: increase the steep of color
signal edge, make the edge of color transition more clearly. Brightness edge
adjustment: increase edge gradient of brightness signal, make the edge of picture
more clearer
18、Super definition display panel
19、Dynamic comb filter
20、Headphones output(not include 02 series)

Ⅱ. Circuit composition of the TV
The LS03 chassis LCD TV is composed of regulating voltage circuit, inverter
circuit, RF circuit, video enhancement circuit, video processing circuit, power
amplifier circuit, VGA circuit, system control circuit and key control circuit. The
block diagram of circuit composition is below:

RF Input

TDA9886

MST718BU

PT2314

S-Video input

YPbPr audio

input

HD/YPbPr

video input

PC

Vedio

input

PC Sound

input

P15V330

To panel

Power Intverter

TDA1517 Loudhailer

Earphone

LA72702

Ⅲ. PCB assembly introduction
All the Signal Processing are in Main board.
1、 Main board assembly
Main board Module is the main part of Signal Processing in LCD TV. The input
signal is converted into uniform digital signal which can be identified by TFT under
the control of system control circuit.
2、 Key board assembly
It is composed of 7 function keys. the user can operate the LCD TV conveniently by
using this assembly.
3、 Remote control receiving board assembly

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It is composed of a work indicator light and a remote receive head. The user use the
remote control box by this module can operate the LCD TV conveniently and know
the LCD TV work condition.
4、 Earphone output board assembly(not include 02 series)
It is composed of a earphone outlet, user can Listen by earphone conveniently.
5、 Inverter board assembly(include inverter circuit)
The function of the inverter is supply power to light tube in TFT , and lighten the back
lamp Unit of TFT module, so the user can see the image on TFT.

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PartⅡ: Function introduction about the main integrated

circuit

. Main ICs and componentsⅠ

Serial
number

Name model Main function

1 U4 MP1430DN-LF-Z Liner voltage IC
2 U8 PI5V330SQEX Video switch
3 U9 24LC21AT/SN EEPROM(save display

parameter information)

4 U23 24LC32AT/SN EEPROM（save user

control information）

5 U16 PT2314 Audio processor
6 U15 TDA1517P Audio power amplifier
7 U19 TDA9886TS/V4 single and

multistandard
alignment-free
IF-PLL demodulators

8 U17 TAF5-C2IP1RW RF tuner
9 U22 MST718BU Processor with Video

Decoder

10 U21 LA72702NVA

US TV BTSC Decoder

. The function introduction of main ICⅡ

1 The MST718BU is a high quality ASIC for NTSC/PAL/SECAM LCD-TV
application. It receives analog NTSC/PAL/SECAM CVBS and S-Video inputs from
TV tuners, DVD or VCR sources, including weak and distorted signals, as well as
analog RGB input from GPS systems. Automatic gain control (AGC) and 10-bit
3-channel A/D converters provide high resolution video quantization. With automatic
video source and mode detection,users can easily switch and adjust variety of signal
sources. Multiple internal adaptive PLLs precisely extract pixel clock from video
source and perform sharp color demodulation. Built-in line-buffer supports adaptive
2-D comb-filter, 2-D sharpening, and synchronization stabler in a condense manner.
The output format of MST718BU supports 8-bit TTL or LVDS digital TFT-LCD
modules.
MST718 FEATURES:

Video Decoder

· Supports NTSC, PAL and SECAM video input formats

·2D NTSC and PAL comb-filter for Y/C separation of CVBS input

·Multiple CVBS and S-video inputs Supports Closed-caption and V-chip

·Supports Teletext 1.5

·ACC, AGC, and DCGC (Digital Chroma GainControl)

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Analog Input

·Supports RGB input format from PC,camcorders and GPS

·Supports YCbCr inputs from conventional videosource and HDTV

·Supports SCART – RGB + Fast Blank

·Supports video input 480i, 480p, 576i, 576p,720p, 1080i; RGB input resolution in
640x480,800x480, 800x600, 1024x768, and 1280x1024(SXGA)

·3-channel low-power 10-bit ADCs integration for YCbCr and RGB

·Supports RGB composite sync input (CSYNC),SOY, SOG, HSYNC, and VSYNC

·On-chip clock synthesizer and PLL

·Auto-position adjustment, auto-phase adjustment, auto-gain adjustment, and
auto-mode detection

Color Engine

·Brightness, contrast, saturation, and hue adjustment

·9-tap programmable multi-purpose FIR (Finite Impulse Response) filter

·Differential 3-band peaking engine

·Vertical peaking

·Spatial noise reduction

·Luminance Transient Improvement (LTI)

·Chrominance Transient Improvement (CTI)

·Black Level Extension (BLE)

·White Level Extension (WLE)

·Favor Color Compensation (FCC)

·3-channel gamma curve adjustment

·Independent 6 color of saturation, hue, and brightness control

Scaling Engine/Panel Interface

·Supports digital panels up to 1366x768, and 1440x900

·Supports single/dual 8-bit LVDS panel outputs

·Supports 8-bit TTL panel output

·Supports various displaying modes

·Supports horizontal panorama scaling

Miscellaneous

·Built-in MCU

·3-wire serial bus interface for configuration setup

·Built-in step-down PWM circuits for input 2.5V

·Built-in internal OSD with 512 programmable fonts, 1、2 or 4 bit per pixel
color,16-color palettes, and 12-bit color resolution

·Supports external OSD

·Support CVBS out

·Spread spectrum clocks

·Optional 3.3V / 5V output pads with programmable driving current

·128-pin PQFP package

MST718 pin function:
Analog Interface

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Pin Name Pin Type Function Pin

VMID

Mid-Scale Voltage Bypass 2

VCLAMP

CVBS/YC Mode Clamp Voltage Bypass 3

REFM

Internal ADC Bottom De-coupling Pin 4

REFP

Internal ADC Top De-coupling Pin 5

PRINP Analog Input Analog Pr Input of HDTV 7

PRINM Analog Input

Reference Ground for Analog Pr Input of
HDTV

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PBINP Analog Input Analog Pb Input of HDTV 9

PBINM Analog Input

Reference Ground for Analog Pb Input of
HDTV

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SOY Analog Input Sync-on-Y slicer input 11

YINP Analog Input Analog Y Input of HDTV 12

YINM Analog Input

Reference Ground for Analog Y Input of
HDTV

13

BINP Analog Input Analog B Input of VGA 14

BINM Analog Input

Reference Ground for Analog B Input of
VGA

15

SOGIN Analog Input Sync-on-Green slicer input 16

GINP Analog Input Analog G Input of VGA 17

GINM Analog Input

Reference Ground for Analog G Input of
VGA

18

RINP Analog Input Analog R Input of VGA 19

RINM Analog Input

Reference Ground for Analog R Input of
VGA

20

C1INP Analog Input Analog Chroma Input for TV S-Video1 /

Analog Composite Input of TV CVBS4

22

C1INM Analog Input Reference Ground for Analog Chroma Input

of TV S-Video1 / Analog Composite Input of
TV CVBS4

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YS1INP Analog Input Analog Luma Input of TV S-Video1 / Analog

Composite Input of TV CVBS3

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YS1INM Analog Input Reference Ground for Analog Luma Input of

TV S-Video1 / Analog Composite Input of
TV CVBS3

25

C2INP Analog Input Analog Chroma Input for TV S-Video2 26

C2INM Analog Input

Reference Ground for Analog Chroma Input
of TV S-Video2

27

YS2INP Analog Input Analog Luma Input of TV S-Video2 28

YS2INM Analog Input

Reference Ground for Analog Luma Input of
TV S-Video2

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CVBS1P Analog Input Analog Composite Input for TV CVBS1 30