Temp TVLCD20161 Service Manual

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LCD TELEVISION

SERVICE MANUAL

Chassis LS07

Please read this manual carefully before service.

CONTENTS

Part :Ⅰ Specification , feature and Composition …………………………………………1

1.1 Technical specification……………………………………………………...................1

1.2 Main feature……………………………………………………………………………1

1.3 Circuit composition………………………………………………………....................2

1.4 PCB assembly introduction………………………………………………...................3

Part :Ⅱ Function introduction about the main integrated circuit …………………………..5

2.1 Main ICs and components……………………………………………………………5

2.2 Function introduction of main IC……………………………………………………5

2.2.1 MST518 high integration chip…………………………………………………...5

2.2.2 TDA15021H introduction……………………………………………..................8

2.2.3 TDA9178 brief………………………………………………………..................12

2.2.4 TDA1517ATW brief…………………………………………………………….14

Part :Ⅲ Signal Processing Flow chart ….…………………………………………………….15

3.1 RF/IF process……………………………………………………………...................15

3.2 Image and sound process……………………………………………………………15

3.3 Digital signal process……………………………………………………...................15

3.4 TV power supply system…………………………………………………………….15

3.5 Location of main components and socket on mainboard and definition………...17

Part : Ⅳ Typical troubleshooting processing flowchart and example………………………20

4.1 Typical troubleshooting flowchart…………………………………………………..20

4.2 The example of service……………………………………………………………….22 PartⅤ: Spare part lists………………………………..………………………………………25

Annex: 1、Circuit schematic diagram 2、Final Assembly diagram 3、Final Wiring Connection diagram

PartⅠ: Specification , feature and Composition

Ⅰ、 Technical Specification: 20 inch LCD TV Physical resolution :640*480(VGA), Audio power output:2*2.0W, Inside power module AC input voltage:AC 100～240V,50/60Hz.

Ⅱ、 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（50/60HZ）,1080i（50/60HZ）,and 1080P

（50/60HZ） formats. 5、Scart input 6、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.

7、Program & child lock function

Capable of locking any program of the TV and the function button of

the front panel. 8、Timer function 9、Blue background with noise reduction

In AV、S-video and YPbPr modes, screen displays soft blue background

if there is no signal input.

10、 Multi Language on-screen display menu

Text and graphical user interface makes the menu operation

user-friendly.

11、 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. 12、Plug-and-play

No additional software is needed when the product is used as computer

terminal display. 13、Automatic picture’s quality adjustment 14、No flicker, no radiation, greenness and health 15、Auto on as time is set 16、Zoom mode

Full-screen 、16:9、cinema、Subtitle 17、Legerity, convenient, low power consumption 18、Picture quality enhancement function Dynamic skin color correct: improve distort color in picture, make

it near to real color. 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 19、Super definition display panel 20、Dynamic comb filter 21、Headphones output 22、10 page teletext

Ⅲ. Circuit composition of the TV The American LS07 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:

Ⅳ. PCB assembly introduction The Constitution of the PCB is easier than LP03 chassis, 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. Main board module contains two parts of signal processing module: Philips UOC3 process analog audio and video circuit mainly, MST518 process VGA circuit、 signal format transform system control circuit mainly. The front module can convert the video IF signal and audio IF signal from tuner into RGB analog signal and audio signal, this part is named analog audio and video decoding process. The RGB color from UOC is received by MST518,then MST518 accomplish A/D converting , output suitable digital color signal to Drive circuit of TFT . 8051 Processor inside UOC is responsible for co-operation work of the each part of system, and respond to user operation which is operated on control panel(key board Module). 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 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 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.

PartⅡ: Function introduction about the main integrated

circuit

Ⅰ. Main ICs and components

serial

number

1 A1 TAF5-E2I21RW2 RF tuner 2 U8、U21 TDA1517ATW Audio power amplifier

3 U3 MST518 AD converter and format transformer

4 U2 UOC(TDA15021H) Video decode and MCU control

U7 TDA9178

5 Q9 Si2311DS MOS switch 6 U11、U12 IRF7316 MOS switch

7 U19 NTMS10P02R2 MOS switch 8 U9、U23 LM2596-5.0 Liner voltage IC

9 U1 24LC21A EEPROM(save display parameter information)

10 U4 24LC32A EEPROM（save user control information） 11 U6、U20 PI5V330A Video switch

Ⅱ. The function introduction of main IC 1 MST518 high integration chip MST518 is a high performance、high integration image processor which is designed for LCD, it can support SXGA format(1280*1024).it integrates a group of AD converter 、high quality format transform system、OSD generator、output clock generator、multiple format output display interface(support TTL、LVDS、RSDS) MST518 feature:

z Have high quality Expand transform and compress transform, can

z Integrated LVDS circuit inside z 8 bit high quality ADC inside z Double VGA input, Software switch z Support ITU-656 format signal input z Support H/V sync、composite sync、green composite sync input, and

z Programmable 10 bit Gamma correct, the brightness and contrast is

z 8 color、256 Character OSD z Built-in DDC circuit inside z Low standby power z Support TTL、double LVDS signal output, Software switch

Name model Main function

Analog signal processor

output XGA format signal

detect automatically by itself

adjustable

MST518 pin function:

And CPU interface

Pin Pin name Pin function

98-91

125

HWRESET CS SDA SCL INT AD [7:0] BUSTYPE

Hardware reset，high voltage enable

Chip select signal of three-wire serial bus

data signal of three-wire serial bus

clock signal of three-wire serial bus

interrupt Parallel bus，the chassis is not used

Bus type select

Analog Interface

HSYNC0 VSYNC0 HSYNC1 VSYNC1 RMID REFP REFM RIN0 RIN0M

SOGIN0 GIN0 GIN0M

BIN0 BIN0M RIN1M

RIN1 GIN1M GIN1

SOGIN1 BIN1M BIN1

REXT

Analog Horizontal sync signal input channel 0

Analog vertical sync signal input channel 0

Analog Horizontal sync signal input channel 1

Analog vertical sync signal input channel 1

Scaler internal reference. voltage internal ADC decouple ＋ internal ADC decouple －

Analog red signal input channel 0

Analog red signal input channel 0 reference

grounding voltage

Green sync signal input channel 0

Analog green signal input channel 0

Analog green signal input channel 0 reference

grounding voltage

Analog blue signal input channel 0

Analog blue signal input channel 0 reference

grounding voltage

Analog red signal input channel 1 reference

grounding voltage

Analog red signal input channel 1

Analog green signal input channel 1 reference

grounding voltage

Analog green signal input channel 1

Green sync signal input channel 1

Analog blue signal input channel 1 reference

grounding voltage

Analog blue signal input channel 1

Outside connect 390 with 3.3V

LCD Interface

145 OCLK 146 LDE 144 LVSYNC

Clock output

enable signal

vertical sync output

143 LHSYNC 138 LVA0M 137 LVA0P 136 LVA1M 135 LVA1P 134 LVA2M 133 LVA2P 128 LVA3M 127 LVA3P 132 LVACKM 131 LVACKP 26-23,18-15 RB[7:0] 14-11, 8-5 GB[7:0] 4,3,154,153,150-147 BB[7:0]

Horizontal sync output LVDS output 0－

LVDS output 0+ LVDS output 1－

LVDS output 1+ LVDS output 2－

LVDS output 2+ LVDS output 3－

LVDS output 3+ LVDS clock signal output－

LVDS clock signal output +

TTL red signal channel

TTL green signal channel

TTL blue signal channel

GPIO Interface

87 GOUT1/PWM1 86 GOUT0/PWM0 2 BYPASS 29 DDC_DAT 30 DDC_CLK 31 DDCROM_CLK 32 DDCROM_DAT 34 XIN 35 XOUT

PWM output 1

PWM output 0

Outside connect filter capacitor

Analog interface DDC data

Analog interface DDC clock

DDC ROM clock

DDC ROM data

Crystal oscillator signal input

Crystal oscillator signal output

Power Pins

48, 54, 58, 77 AVDD 56 AVDD_PLL 36 AVDD_MPLL 10, 22, 88, 99, 111, 129, 139, 151 19, 102, 114, 142 VDDC 1, 9, 20, 21, 37, 42, 45, 51, 57, 59, 76, 81, 89, 100, 101, 112, 113, 130, 140, 141, 152

VDDP

GND

A/D convert power supply

PLL power supply

MPLL power supply

Digital signal output power supply

Digital circuit power supply

Digital circuit ground

MST518 inner diagram：

2 TDA15021H introduction: The third-generation super integrated circuit UOC III which designed by Philips company recently integrates with video decode、2D comb filter、 high quality audio process technique, suitable with US closed caption and V-chip function, compatible with single series IC. The series of UOC III have high integrity, besides completing the Processing of all small signal(IF signal demodulation, video decode ,H/V signal, sound DSP),and integrate all the MCU function. It has many Advantages ,example: the compact circuit、good performance、simple craft , etc. it matches with company’s demand of high performance price ratio and high product efficiency . It is suitable for 4:3 or 16:9、50/60HZ and 100/120HZ TV system, the main characteristic is below:

z multi-system IF demodulation、analog video decode z comb filter internal z NICAM、stereo auto identify and decode z support 4:3、16:9 display format z 4 CVBS or 3 Y/C input,1 CVBS output,2 YCrCb/2 RGB input z 4 AV audio input,1 AV adjustable audio volume output z volume auto level control circuit z global FM demodulation z picture quality enhancement of dynamic peak value control、skin color

correct、Gamma correct、Black level extension, etc

z Can turn off horizon and vertical scan part，output H/V sync. signal

to Scaler

z 128K Flash Memory inside, support program on line z Automatic Y/C signal identify

TDA15011H pin function:

pin Pin name Pin function

1 VSSP2 Grounding

2 VSSC4 Grounding

3 VDDC4 +1.8V

4 VDDA3 +3.3V

5 VREF_POS_LSL +3.3V

6 VREF_NEG_LSL+HPL 0V

7 VREF_POS_LSR+HPR +3.3V

8 VREF_NEG_HPL+HPR 0V

9 VREF_POS_HPR +3.3V

10 XTALIN crystal oscillator input

11 XTALOUT crystal oscillator output

12 VSSA1 Grounding

13 VGUARD/SWIO Protecting voltage input or I/O

14 DECDIG DECDIG signal input

15 VP1 +5V

16 PH2LF The second grade horizontal phase lock filter

17 PH1LF The first grade horizontal phase lock filter

18 GND1 Grounding

19 SECPLL SECAM PLL decouple

20 DECBG Inside reference voltage decouple

21 EWD/AVL VDD5A voltage input

22 VDRB TV vertical sync signal output

23 VDRA vertical sync output

24 VIFIN1 VIF input 1

25 VIFIN2 VIF input 2

26 VSC Outside connect vertical ramp capacity

27 IREF Reference current input

28 GNDIF IF grounding

29 SIFIN1 SIF input 1

30 SIFIN2 SIF input 2

31 AGCOUT tuner RF AGC control voltage output

32 EHTO overvoltage protection input

33 SSIF MUTE control signal input

34 AUDIOIN5L Av left track signal input

35 AUDIOIN5R Av right track signal input

36 AUDOUTSL SCART/CINCH left track output

37 AUDOUTSR SCART/CINCH right track output

38 DECSDEM Track demodulator decouple

39 QSSO Deemphasis capacitor

40 GND2 grounding

41 PLLIF IF_PLL filter

42 SIFAGC Sound intermediate frequency auto gain control

43 IFVO IF demodulation video output

44 FMRO FM broadcast output

45 VCC8V The supply voltage of Sound switch

46 AGC2SIF The second sound intermediate frequency auto gain

control

47 VP2 +5V

48 IFVO The video output of Choose channel

49 AUDIOIN4L HD signal left track audio output

50 AUDIOIN4R HD signal right track audio output

51 CVBS4/Y4 S-video luminance signal input

52 C4 S-video chroma signal input

53 AUDIOIN2L PC signal left track audio input

54 AUDIOIN2R PC signal right track audio input

55 CVBS2/Y2 AV CVBS signal input

56 AUDIOIN3L Inside DVD module left track audio input

57 AUDIOIN3R Inside DVD module right track audio input

58 CVBS3/Y3 Inside DVD module brightness signal input

59 C2/C3 Inside DVD module chroma signal input

60 AUDOUTLSL Main channel left track output

61 AUDOUTLSR Main channel right track output

62 AUDOUTHPL Earphone channel left track output

63 AUDOUTHPR Earphone channel right track output

64 CVBS/PIP CVBS/PIP output

65 SVM Scan modulate output

66 FBISO flyback input/sandcastle output or composite H/V

timing output

67 HOUT Horizontal sync signal output

68 VSScomb Grounding

69 VDDcomb +5V

70 VIN V signal input

71 UIN U signal input

72 YIN Y signal input

73 YSYNC Y signal input for Sync separate

74 YOUT Y signal output

75 UOUT U signal output

76 VOUT V signal output

77 INSSW3 RGB/YpbPr insert identify signal input

78 R/PrIN3 R/Pr signal input

79 G/YIN3 G/Y signal input

80 B/PbIN3 B/Pb signal input

81 GND3 grounding

82 VP3 +5V

83 BCLIN beam current limiter input

84 BLKIN Black current input

85 RO R basic color signal input

86 GO G basic color signal output

87 BO B basic color signal output

88 VDD3 +3.3V

89 VREFAD_NEG 0V

90 VREFAD_POS +3.3V

91 VREFAD Audio ADC reference voltage

92 GNDA grounding

93 VDDA +1.8V

94 VDD3A +3.3V

95 VSSADC grounding

96 VADC +1.8V

97 INT0 Remote control signal input

98 P10/INT1 DPF clock line

99 P11/T0 DPF data line

100 VDDC2 +1.8V

101 VSSC2 grounding

102 P04/12SWS MST reset signal

103 P03/12SCLK HD_PC select control signal

104 P02/12SDO2 Power Amplifier standby control signal

105 P01/12SDO1 TV_DPF select control signal

106 P00/12SDII/O Turn on control signal

107 P13/T1 MST chip select signal

108 P16/SCL UOCI2C bus clock line

109 P17/SDA UOCI2C bus data line

110 VDDP +3.3V

111 P20/TPWM Red indicator light control signal

112 P21/PWM0 green indicator light control signal

113 P22/PWM1 TFT power supply control signal

114 P23/PWM2 Inside DVD module power supply control signal

115 P30/ADC0

116 P31/ADC1 Earphone insert identify signal input

117 VDDC1 +1.8V

118 VDD18 +1.8V

119 P32/ADC2 DVD key-press signal input

120 P33/ADC3 TV key-press signal input

121 VSSC grounding

122 P24/PWM3 Background control signal output

123 P25/PWM4 SAW filter control signal

124 VDDC3 +1.8V

125 VSSC3 grounding

126 P12/INT2 MST interrupt signal input

127 P14/RX MST data line

128 P15/TX MST clock line

Reserve IO port

TDA15021H inside block diagram

3、TDA9178 brief

TDA9178 is a analog signal processor with standard YUV input and output interface .It provide three main process function: luminance vector, color vector and spectrum process. It can finish comprehensive picture improving function independently. The characteristic of the TDA9178 is below:

a) Luminance Transient Improvement (LTI), Color Transient

Improvement (CTI)

b) Variable gamma control c) Self-suitable black level extention control d) Skin color correction, green intensity ,blue extend e) Noise measurement and reduced noise processing function f) Line Width Control (LWC)

TDA9178 PIN DESCRIPTION:

Pin Pin name Function

sandcastle input not connected ADC input 1 ADC input 2 ADC input 3 luminance input

sandcastle input

Grounding

A/D convertor input 1

A/D convertor input 2

A/D convertor input 3

Y input

address selection input U signal input V signal input test pin serial clock input (I2C-bus) not connected not connected serial data input/output

2C-bus)

(I decoupling digital supply V signal output U signal output ground luminance output supply voltage SCAVEM output not connected not connected

TDA9178 inside block diagram:

I2C address choose input terminal

U input

V input

Grounding

I2C bus clock signal

Not connected

I2C bus data signal

connect decouple capacitor external

V signal output

U signal output

Ground

Y signal input

Supply power

Scan velocity modulate output

Grounding

4、TDA1517ATW brief:

The TDA1517ATW is an double channel class-AB power amplifier contained in a plastic heat sink thin shrink small outline package (HTSSOP20). The device is primarily developed for multimedia applications.

a) Outside circuit is simple b) Mute、standby is controllable c) Temperature protect circuit d) low noise switch e) Constant gain

TDA1517 PIN DESCRIPTION:

Pin Pin name function

8、9 12、13 15、16

1、2、4、6、 7、10、11、

14、19、20

non-inverting input supply voltage ripple rejection Output N.C. supply voltage mode select switch inverting input

GND ground

Audio input

Bias circuit filter

Audio output

Not connected ＋12V power supply

Work mode select Reverse input terminal （connect capacitor to ground ）

TDA1517 inside block diagram:

PartⅢ: Signal Processing Flow chart

This chapter mainly introduces analog signals process、video intensify process、TV system control process、TV supply system. Ⅰ. analog signals process 1、 IF/RF process Completed by TAF5-E2I21RW2 RF tuner, output IF signal. The Function of RF tuner is below:

Pin symbol function

1 AGC Auto gain control voltage

2 TU The TV do not connect

3 ADD ground

4 SCL I2C bus（clock ）

5 SDA I2C bus（data ）

6 BM +5V power supply

7 BM +5V power supply

8 NC Not connected 9 BTL +32V power supply，form 0～32V tune voltage

10 NC Not connected

11 IF IF signal output

2、 Image and sound process

UOC chip receives the IF signal separated from SAW filter, detects and decodes. Output RGB color analog signals from the 85、86、87 pin respectively. Output the main channel L、R audio signal from 60、61 pin. Output earphone channel L、R audio signal from 62、63 pin. Moreover, AV、S-Video、YC signal of inside DVD(some types of TV have not) is also decoded inside of UOC chip, switched with TV input in UOC and output one way RGB color analog signal, send it to back-end process. 3、 Digital signal process

The analog RGB signal output from UOC and RGB signal output from DFP are switched and selected by a PI5V330A,input it into the 65、63、60 pin Of MST518. The RGB signal output from computer and HD-YPbPr signal are switched and selected by another PI5V330A,input into the 75、72、70 of MST518.This two channel RGB signal are switched inside MST518,then AD conversion, video format transition, at last output digital color signal which is suitable for TFT drive circuit. MST518 finishes the pixels ratio converting of input video signal、the image auto optimization process ,then process via memory buffer、scaler、chroma matrix circuit、 chroma look-up table、chroma space gain, etc. Output corresponding standard physical resolution digital color signal and corresponding sync, clock signal to TFT, control the TFT to display image correctly. 4、TV power supply system: (1) The supply power system of the main IC is below:

z 12V:the unit main power supply

z +34V:RF tuner tune voltage z VCC5: stable and constant +5V power supply z VCC5A: +5V power supply software can turn off z V3_3D:UOC digital part supply power supply z V1_8V1:UOC digital part constant supply power supply z V1_8V2:UOC digital part power supply can be turned off z V2_5M:MST518 digital core supply power supply z V3_3M:MST518 supply power supply

(2) The constitution and distributing of the TV

5、The location of main components and socket on mainboard and definition

14 15

16 17 18

Socket definition

number name Connect object Function description

1 JP1 Connect inside power

supply board module

2 JP2 Connect outside power

adapter

3 J8 Connect outside VGA

audio input

4 J1 Connect outside VGA input

5 J3 Connect outside HD-YPbPr

input

6 J4 Connect outside HD audio

input

7 J2 Connect outside SCART

signal input

10 J9 Connect inside DVD signal

input

12 J7 Connect inside DVD K

board

13 J12 Connect earphone output

board

14 J14 Connect speaker

15 J13 Connect speaker 16 J6 Connect TV K board Look circuit diagram ，the second pin is 3.3V

17 J5 Connect remote control

receiving board

18 J11 UOC debug socket Not used

19 J10 DPF digital photo-frame

signal input

20 J17 Connect display screen

（TTL panel）

21 J16 Connect display screen

（LVDS panel）

22 J22 Connect display screen

（TTL panel）

23 J15 MST518 debug socket Not used

24 J19 Supply DVD or DPF power Not used

Not used

Look circuit diagram，the fifth pin is 3.3V

Not used

CMO 20” panel

Not used

25 J18 Connect inverter +12V, +12V, backlight switch，GND, GND,GND

Description of Main component

No. name

element

Function description

A B U2 C U3

A1 RF tuner TAF5-E2I21RW2 RF input, IF output

UOC(TDA15021H) Video decode and MCU control

MST518 AD converter and format transformer

D U20 PI5V330A Video switch on/off E U6 PI5V330A Video switch on/off F U11 G U9 H U23 I U19 J U21 K U8 L U4 M Q9 N U12 O U1

IRF7316 MOS switch

LM2596-5.0 Linear voltage IC

NTMS10P02 MOS switch

TDA1517ATW Audio power amplifier

24LC32A EEPROM(store user control information)

Si2311DS MOS switch

IRF7316 MOS switch

24LC21A EEPROM(store display parameter information)

PartⅣ: Typical troubleshooting processing flowchart and

Example

Ⅰ.

Typical troubleshooting flowchart

1、No anything(haven’t sound ,haven’t picture, haven’t indicator light),and no respondence to key、remote control.

No answer,no respondence to

key and remote control button

YES

The connection of

Main board and key

board ,remote control

board is reliable or not?

Check each supply power pins

voltage of U13、U22 output to

U2 are correct or not?

YES One pin has no voltage

Connect the wire

again

repair or change

adapter

Check U13、U22

Outside circuit

NO YES

Is outside adapter(or inside)

output 12V normal?

YES

Is U13、U22 output

port voltage normal?

1、check peripheral parts of

Change U2

supply power pin . 2、check the soldered joint is OK or not.

2、 Have sound no picture, indicator light work normally

indicator light work,but black screen

when pressing down the power supply

Observe back lamp is on or off

key

Check U 13、 U22

Ou tside circu it

YES

U13、 U22 output voltage

is normal or not?

YES

YES One pin no voltage

Change U2

Check each supply power pin voltage

which output from U13、 U22 to U2 is

normal or not?

1、 check supply pow er pin outside parts of an apparatus 2、 check the jointin g is O K or not

Cheeck inverter supply

power voltage and

connect line

3、White screen: The reason of the troubleshoot is the signal electrode electrode haven’t working voltage. The TFT is always in transparent condition, so the whole screen is in white raster.

VLCD of screen socketJ16(J17、J2 2)

on main boar d is nor mal or no t?

Check Q25、U19、FB39、

FB40、FB41, etc related parts

osc illograph to check the si gnal input

YES

Check PCB copper c onnect l ine

YES

Switch signal source, use the

or not

YES

Check the s oldering of screen socke t on

main board i s OK or not?

Patch s older

Check U2 pe ripheral circuit is normal or

not ,change the t rouble par ts.

4、 Picture abnormal、color abnormal 、short of color

switch signal so urce,Observe if the picture

is a bnormal in some mode condition

picture abnormal in TV、AV

C he c k U2 0 an d i t’s

circuit ,check the Q12、

Q14、 Q1 5 is nor ma l o r

condition

peripheral

not

normal

Ch eck th e ou tpu t of 85th 、

86 t h、87th pin of U2

Check FB1 、FB2、FB3、

FB4、FB5 inducta nce are

picture abnormal in HD、

VGA co nditi on

Ch ec k U6 and it ’s ou ts id e ci rcui t i s

normal or not

no rmal

normal or not

pi cture abnormal in all mode

Check the solder joint of

screen socke t J 16、J17、

J22 on main board is OK or not,the connection is OK or

no t

no rma l

Chec k per iph era l

circuit of U2 is normal

or not,change trouble

pa r t

Ⅱ、 The example of service

Example 1: Can’t turn on the TV

1、troubleshoot phenomenon: After connect power supply line and turn

on the power supply ,no logo appear on screen. Press any key or use the remote control box, the TV has no reflection, no display and black screen. The process of maintenance : Remove the plug of adapter output, measure adapter output voltage is +12V,the adapter works normally. check the connection with key board、remote control receiving board and mainboard. If they are ok, the problem must be MCU not work. First check supply power of U2 chip. Connect power supply, then measure the voltage of the 2、4 pin of U13 NTMS10P02 is 0.2V,and over-heat , the reason must be short circuit of power supply backend. You should remove the plug quickly, otherwise the chip must be bad. Use the multimeter to measure ，confirm it is short circuit to ground. The places which connect U2 with 3.3V voltage are so many, you should disconnect and measure it one by one. when you disconnect the C68, it is normal, So it is caused by C68 Short circuit to grounding.

Example 2: No picture in VGA mode

2. Troubleshooting phenomenon: in TV/AV mode ,the image and sound is

ok, PC (in VGA mode) is no picture, but have state icon. The process of maintenance: first check the signal source, signal socket、plug are ok or not. Because during switch the mode, the image display normally in non-PC mode ,it is proved that the backend image public processing channel is ok, namely U3 MST518 and backend image signal processing circuit work normally. In PC mode, measure the arbitrary pin of 4,7,12 pin , image data port of U6 P15V330A by oscillograph, there are no waveform, change U6P15V330A and the Troubleshooting phenomenon disappear.

Example 3: no picture in VGA mode and the “signal beyond boundary” is

appeared on screen.

3. Troubleshooting phenomenon: no picture in VGA mode and the “signal

beyond bound” is appeared on screen. in TV/AV mode, image、sound is ok. The process of maintenance: first check the signal output from the signal source is standard or not, or beyond the resolution which is supported by TFT panel. except of the two cases, the phenomenon comes from the TFT display. Under general circumstance it is caused by the abnormal of the horizon sync impulse ,vertical sync impulse of VGA signal. Inspect the 38th、39th pin of U3 by oscillograph, find the magnitude of horizon sync impulse is below the normal, measure the waveform of 13th pin of VGA J1 ,if it is ok, so maybe the value of resistor R23 will be largen, measure the resistance of R23 is 10K ,but the rating resistance is 1K, so it

is obvious that the magnitude of horizon sync. impulse is attenuated too much caused by value of couple resistance R23 become large. So the pixel clock inside of the MST518 can not vibrate, result in the A/D converter of MST518 internal can not work normally . So appear no picture in VGA mode and “signal beyond boundary” on TFT screen.

Example 4: Can control TV by remote control, but can not control TV

by key board

4. Troubleshooting phenomenon: image、sound is ok under any source, use remote control to operate each function is ok, but can not control by using the key board, failure completely. The process of maintenance: first check the socket of J6 on mainboard ,the solder joint and touch of connector are ok or not. if it is ok, check the key board ,measure each resistance, find R1 open circuit, change it .

Example 5: the image is ok after turn on the TV, but left speaker has

no sound output

5. Troubleshooting phenomenon: the image is normal in TV mode, but the left speaker has no sound output, using remote control to

operate ,each function is ok. use AV、PC audio input ,is still no sound output. The process of maintenance: measure the waveform from 60th pin of UOC by oscillograph, according to signal flowchat, measure R227、 R157、U8、C130 one by one, and observe the waveform is ok or not, find the back end of C130 have not waveform, change C130 and troubleshooting disappear .