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LCD TELEVISION
SERVICE MANUAL
Chassis LS07
Please read this manual carefully before service.
CONTENTS
Part: 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: 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: 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: Typical troubleshooting processing flowchart and example...........................20
4.1 Typical troubleshooting flowchart...........................................................20
4.2 The example of service.........................................................................22
Part: Spare part lists...................................................................................25
Annex: 1Circuit schematic diagram
2Final Assembly diagram
3Final Wiring Connection diagram
Part: Specification , feature and Composition
Technical Specification:
20 inch LCD TV
Physical resolution :640*480(VGA), Audio power output:2*2.0W, Inside
power module AC input voltage:AC 100240V,50/60Hz.
Main feature
1Radio frequency input
It can receive CATV signal.
2AV input
Convenient for watching a DVD player,VCR,pickup camera or other
playback devices.
3S-video input
Convenient of receiving a high quality component signal from a DVD
player.
4YPbPr input
Capable of receiving the high definition YPbPr signal in
480i,480P,576i,576P,720P50/60HZ,1080i50/60HZ,and 1080P
50/60HZ formats.
5Scart input
6VGA 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.
7Program & child lock function
Capable of locking any program of the TV and the function button of
the front panel.
8Timer function
9Blue background with noise reduction
In AVS-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.
12Plug-and-play
No additional software is needed when the product is used as computer
terminal display.
13Automatic picture's quality adjustment
14No flicker, no radiation, greenness and health
15Auto on as time is set
16Zoom mode
Full-screen 16:9cinemaSubtitle
17Legerity, convenient, low power consumption
18Picture 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
19Super definition display panel
20Dynamic comb filter
21Headphones output
2210 page teletext
. Circuit composition of the TV
The American LS07 chassis LCD TV is composed of regulating voltage
circuitinverter Circuit RF circuitvideo enhancement circuitvideo
Processing circuitPower amplifier circuitVGA circuitsystem control
circuit and key control circuit. The block diagram of circuit composition
is below:
. 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.
Part: Function introduction about the main integrated
circuit
. Main ICs and components
serial
Name model Main function
number
1 A1 TAF5-E2I21RW2 RF tuner
2 U8U21 TDA1517ATW Audio power amplifier
3 U3 MST518 AD converter and format transformer
4 U2 UOC(TDA15021H) Video decode and MCU control
U7 TDA9178 Analog signal processor
5 Q9 Si2311DS MOS switch
6 U11U12 IRF7316 MOS switch
7 U19 NTMS10P02R2 MOS switch
8 U9U23 LM2596-5.0 Liner voltage IC
9 U1 24LC21A EEPROM(save display parameter information)
10 U4 24LC32A EEPROMsave user control information
11 U6U20 PI5V330A Video switch
. The function introduction of main IC
1 MST518 high integration chip
MST518 is a high performancehigh 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 systemOSD
generatoroutput clock generatormultiple format output display
interface(support TTLLVDSRSDS)
MST518 feature:
Have high quality Expand transform and compress transform, can
output XGA format signal
Integrated LVDS circuit inside
8 bit high quality ADC inside
Double VGA input, Software switch
Support ITU-656 format signal input
Support H/V synccomposite syncgreen composite sync input, and
detect automatically by itself
Programmable 10 bit Gamma correct, the brightness and contrast is
adjustable
8 color256 Character OSD
Built-in DDC circuit inside
Low standby power
Support TTLdouble LVDS signal output, Software switch
MST518 pin function:
And CPU interface
Pin Pin name Pin function
33 HWRESET Hardware resethigh voltage enable
82 CS Chip select signal of three-wire serial bus
83 SDA data signal of three-wire serial bus
84 SCL clock signal of three-wire serial bus
85 INT interrupt
98-91 AD [7:0] Parallel busthe chassis is not used
125 BUSTYPE Bus type select
Analog Interface
38 HSYNC0 Analog Horizontal sync signal input channel 0
39 VSYNC0 Analog vertical sync signal input channel 0
40 HSYNC1 Analog Horizontal sync signal input channel 1
41 VSYNC1 Analog vertical sync signal input channel 1
78 RMID Scaler internal reference. voltage
79 REFP internal ADC decouple
80 REFM internal ADC decouple
75 RIN0 Analog red signal input channel 0
74 RIN0M Analog red signal input channel 0 reference
grounding voltage
73 SOGIN0 Green sync signal input channel 0
72 GIN0 Analog green signal input channel 0
71 GIN0M Analog green signal input channel 0 reference
grounding voltage
70 BIN0 Analog blue signal input channel 0
69 Analog blue signal input channel 0 reference
BIN0M
grounding voltage
66 RIN1M Analog red signal input channel 1 reference
grounding voltage
65 RIN1 Analog red signal input channel 1
64 Analog green signal input channel 1 reference
GIN1M
grounding voltage
63 GIN1 Analog green signal input channel 1
62 SOGIN1 Green sync signal input channel 1
61 Analog blue signal input channel 1 reference
BIN1M
grounding voltage
60 BIN1 Analog blue signal input channel 1
55 REXT Outside connect 390 with 3.3V
LCD Interface
145 OCLK Clock output
146 LDE enable signal
144 LVSYNC vertical sync output
143 LHSYNC Horizontal sync output
138 LVA0M LVDS output 0
137 LVA0P LVDS output 0+
136 LVA1M LVDS output 1
135 LVA1P LVDS output 1+
134 LVA2M LVDS output 2
133 LVA2P LVDS output 2+
128 LVA3M LVDS output 3
127 LVA3P LVDS output 3+
132 LVACKM LVDS clock signal output
131 LVACKP LVDS clock signal output +
26-23,18-15 RB[7:0] TTL red signal channel
14-11, 8-5 GB[7:0] TTL green signal channel
4,3,154,153,150-147 BB[7:0] TTL blue signal channel
GPIO Interface
87 GOUT1/PWM1 PWM output 1
86 GOUT0/PWM0 PWM output 0
2 BYPASS Outside connect filter capacitor
29 DDC_DAT Analog interface DDC data
30 DDC_CLK Analog interface DDC clock
31 DDCROM_CLK DDC ROM clock
32 DDCROM_DAT DDC ROM data
34 XIN Crystal oscillator signal input
35 XOUT Crystal oscillator signal output
Power Pins
48, 54, 58, 77 AVDD A/D convert power supply
56 AVDD_PLL PLL power supply
36 AVDD_MPLL MPLL power supply
10, 22, 88, 99, 111,
VDDP Digital signal output power supply
129, 139, 151
19, 102, 114, 142 VDDC Digital circuit power supply
1, 9, 20, 21, 37, 42,
45, 51, 57, 59, 76,
81, 89, 100, 101, GND Digital circuit ground
112, 113, 130, 140,
141, 152
MST518 inner diagram
2 TDA15021H introduction:
The third-generation super integrated circuit UOC III which designed by
Philips company recently integrates with video decode2D 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 circuitgood performancesimple craft , etc. it matches with
company's demand of high performance price ratio and high product
efficiency . It is suitable for 4:3 or 16:950/60HZ and 100/120HZ TV
system, the main characteristic is below:
multi-system IF demodulationanalog video decode
comb filter internal
NICAMstereo auto identify and decode
support 4:316:9 display format
4 CVBS or 3 Y/C input,1 CVBS output,2 YCrCb/2 RGB input
4 AV audio input,1 AV adjustable audio volume output
volume auto level control circuit
global FM demodulation
picture quality enhancement of dynamic peak value controlskin color
correctGamma correctBlack level extension, etc
Can turn off horizon and vertical scan partoutput H/V sync. signal
to Scaler
128K Flash Memory inside, support program on line
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 Reserve IO port
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
TDA15021H inside block diagram
3TDA9178 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
1 sandcastle input sandcastle input
2 not connected Grounding
3 ADC input 1 A/D convertor input 1
4 ADC input 2 A/D convertor input 2
5 ADC input 3 A/D convertor input 3
6 luminance input Y input
7 address selection input I2C address choose input terminal
8 U signal input U input
9 V signal input V input
10 test pin Grounding
11 serial clock input (I2C-bus) I2C bus clock signal
12 not connected Not connected
13 not connected Not connected
14 serial data input/output I2C bus data signal
(I2C-bus)
15 decoupling digital supply connect decouple capacitor external
16 V signal output V signal output
17 U signal output U signal output
18 ground Ground
19 luminance output Y signal input
20 supply voltage Supply power
21 SCAVEM output Scan velocity modulate output
23 not connected Grounding
24 not connected Grounding
TDA9178 inside block diagram:
4TDA1517ATW 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) Mutestandby is controllable
c) Temperature protect circuit
d) low noise switch
e) Constant gain
TDA1517 PIN DESCRIPTION:
Pin Pin name function
3 non-inverting input Audio input
5 supply voltage ripple rejection Bias circuit filter
89 Output Audio output
1213 N.C. Not connected
1516 supply voltage 12V power supply
17 mode select switch Work mode select
18 inverting input Reverse input terminal connect capacitor to
ground
1246 GND ground
71011
141920
TDA1517 inside block diagram:
Part: Signal Processing Flow chart
This chapter mainly introduces analog signals processvideo intensify
processTV system control processTV supply system.
. 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 busclock
5 SDA I2C busdata
6 BM +5V power supply
7 BM +5V power supply
8 NC Not connected
9 BTL +32V power supplyform 032V 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 858687 pin
respectively. Output the main channel LR audio signal from 6061 pin.
Output earphone channel LR audio signal from 6263 pin.
Moreover, AVS-VideoYC 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 656360 pin
Of MST518. The RGB signal output from computer and HD-YPbPr signal are
switched and selected by another PI5V330A,input into the 757270 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 signalthe image auto optimization
process ,then process via memory bufferscalerchroma matrix circuit
chroma look-up tablechroma 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.
4TV power supply system:
(1) The supply power system of the main IC is below:
12V:the unit main power supply
+34V:RF tuner tune voltage
VCC5: stable and constant +5V power supply
VCC5A: +5V power supply software can turn off
V3_3D:UOC digital part supply power supply
V1_8V1:UOC digital part constant supply power supply
V1_8V2:UOC digital part power supply can be turned off
V2_5M:MST518 digital core supply power supply
V3_3M:MST518 supply power supply
(2) The constitution and distributing of the TV
5The location of main components and socket on mainboard and definition
25 10
A
N
12
7 13
14
M
K
15
16
6
B J
17
L 18
19
5
20
D
O C 22
21
E
4
F
I 23
3
24
2 G H
1
Socket definition
number name Connect object Function description
1 JP1 Connect inside power
supply board module
2 JP2 Connect outside power Not used
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 Not used
input
12 J7 Connect inside DVD K Not used
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 Look circuit diagramthe fifth pin is 3.3V
receiving board
18 J11 UOC debug socket Not used
19 J10 DPF digital photo-frame Not used
signal input
20 J17 Connect display screen CMO 20" panel
TTL panel
21 J16 Connect display screen Not used
LVDS panel
22 J22 Connect display screen Not used
TTL panel
23 J15 MST518 debug socket Not used
24 J19 Supply DVD or DPF power Not used
25 J18 Connect inverter +12V, +12V, backlight switchGND, GND,GND
Description of Main component
No. name element Function description
A A1 RF tuner TAF5-E2I21RW2 RF input, IF output
B U2 UOC(TDA15021H) Video decode and MCU control
C U3 MST518 AD converter and format transformer
D U20 PI5V330A Video switch on/off
E U6 PI5V330A Video switch on/off
F U11 IRF7316 MOS switch
G U9 LM2596-5.0 Linear voltage IC
H U23 LM2596-5.0 Linear voltage IC
I U19 NTMS10P02 MOS switch
J U21 TDA1517ATW Audio power amplifier
K U8 TDA1517ATW Audio power amplifier
L U4 24LC32A EEPROM(store user control information)
M Q9 Si2311DS MOS switch
N U12 IRF7316 MOS switch
O U1 24LC21A EEPROM(store display parameter information)
Part: Typical troubleshooting processing flowchart and
Example
. Typical troubleshooting flowchart
1No anything(haven't sound ,haven't picture, haven't indicator
light),and no respondence to keyremote control.
No answer,no respondence to
key and remote control button
NO Is outside adapter(or inside) YES
output 12V normal?
The connection of
repair or change Main board and key
adapter board ,remote control
YES board is reliable or not? NO
Is U13U22 output Connect the wire
port voltage normal? again
NO YES
Check U13U22 Check each supply power pins
Outside circuit voltage of U13U22 output to
U2 are correct or not?
YES One pin has no voltage
1check peripheral parts of
supply power pin .
Change U2
2check the soldered joint is
OK or not.
2 Have sound no picture, indicator light work normally
in d ica to r lig h t w o rk ,b u t b la ck screen
w h en p ressin g d o w n th e p o w er su p p ly
k ey
O b serv e b ack lam p is o n o r o ff
YES NO
U 1 3 U 2 2 o u tp u t v o ltag e C h eec k in v e rter su p p ly
is n o rm al o r n o t? p o w er v o ltag e an d
c o n n ect lin e
NO YES
C h eck U 1 3 U 2 2 C h ec k e ach su p p ly p o w er p in v o ltag e
O u tsid e circu it w h ich o u tp u t fro m U 1 3 U 2 2 to U 2 is
n o rm al o r n o t?
YES O n e p in n o v o ltag e
1 ch eck su p p ly p o w e r p in o u tsid e
C h an g e U 2 p arts o f an ap p aratu s
2 ch eck th e jo in tin g is O K o r n o t
3White 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(J17J22)
on main board is normal or not?
NO YES
Check Q25U19 FB39 Check the soldering of screen socket on
FB40FB41, etc related parts main board is OK or not?
YES NO
Switch signal source,use the
oscillograph to check the signal input Patch solder
or not
YES NO
Check U2 peripheral circuit is normal or
Check PCB copper connect line
not ,change the trouble parts.
4 Picture abnormalcolor abnormal short of color
switch signal source,Observe if the picture
is abnormal in some mode condition
picture abnormal in HD picture abnormal in all mode
picture abnormal in TVAV
condition VGA condition
Check U20 and it's Check the solder joint of
Check U6 and it's
peripheral outside circuit is screen socket J16J17
circuit ,check the Q12 J22 on main board is OK or
normal or not not,the connection is OK or
Q14Q15 is normal or
not not
normal normal
normal
Check the output of 85th Check FB1FB2FB3 Check peripheral
86th87th pin of U2 FB4FB5 inductance are circuit of U2 is normal
normal or not or not,change trouble
part
The example of service
Example 1: Can't turn on the TV
1troubleshoot 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 boardremote 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 pin of U13 NTMS10P02 is 0.2V,and
4
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
socketplug 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, imagesound
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 38th39th pin of U3 by
oscillograph, find the magnitude of horizon sync impulse is below
th
the normal, measure the waveform of 13 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: imagesound 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 AVPC audio input ,is still no
sound output.
th
The process of maintenance: measure the waveform from 60 pin of
UOC by oscillograph, according to signal flowchat, measure R227
R157U8C130 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 .
Part: Spare part lists
Spare part lists:
20 inch LCD TV
Material
Material name typemodule NO. remark
code
Mainboard
module JUJ6.690.033 8669000330J
Remote control
receiving board
module JUJ6.694.016 8669400160J
Key board
module JUJ6.694.015 8669400150J
Earphone output
board module JUJ6.695.002 8669500020J
TFT V201V1-T03 50890010130
INVERTER module INV18-605D 59324106054
Dynamoelectric
speaker Y38106-01-5W-4 56231105043
Remote control KLC5A 8201803510L
Inside Power supply
module FSP084-1CD02C 67128084025
Annex: 1Circuit schematic diagram
Main board
K board
Earphone board
Remote control receiving board
Annex 3 Final Assembly diagram
Annex 4 Final Wire Connection diagram