AOC L20W451T User manual

20” LCD TV AOC L20W451T
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Service
Service
Service
TABLE OF CONTENTS
Description Page Description Page
SAFETY NOTICE
ANY PERSON ATTEMPTING TO SERVICE THIS CHASSIS MUST FAMILIARIZE HIMSELF WITH THE
CHASSIS AND BE AWARE OF THE NECESSARY SAFETY PRECAUTIONS TO BE USED WHEN SERVICING
ELECTRONIC EQUIPMENT CONTAINING HIGH VOLTAGE.
Table Of Contents.......……..............................…........1
Revision List.…........................................……......2
Important Safety Notice.……..................……......3
1.General Specifications..............................………........4
2.Operating Instructions………..…………………….......5
2.1.The Use of Remote Control…................……...........5
2.2.To Use the Menu………..............................…...........7
2.3.LCD TV Description…….…..............……...............15
2.4.Interface Connector……............................…...........15
3.White Balance Luminance Adjustment….…........16
4.Input/Output Description……..…………… ...........20
4.1.D-SUB Connector……...…………………....….......20
4.2.Factory Preset Display Modes……………..….....21
5.Front Panel Control Knobs…....................................21
6.Repair Flow Chart……...............................................22
7.Mechanical Instructions……………................28
8.PCB Layout..…………......................................32
8.1.Main Board……….....…….................................32
8.2.Power Board…...………...................................35
8.3.Tuner Board…………........................................37
8.4.IR Board……………….......................................40
8.5.Key Board………………......................................40
8.6.Headphone Board………..................................41
9.Block Diagram………………..............................42
10.Schematic Diagram………………...............…43
10.1.Main Board.............................................43
10.2.Power Board....……....................................56
10.3.Tuner Board....……....................................57
11.Exploded View………..….......................................61
12.BOM List…….……………………………….............62
CAUTION: USE A SEPARATE ISOLATION TRANSFOMER FOR THIS UNIT WHEN SERVICING

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Revision List
Revision Date Revision History TPV Model
A00 Jan-18-07 First Version Release EAF5MTNBC2TETMP

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Important Safety Notice
Proper service and repair is important to the safe, reliable operation of all AOC Company Equipment. The service
procedures recommended by AOC and described in this service manual are effective methods of performing service
operations. Some of these service operations require the use of tools specially designed for the purpose. The
special tools should be used when and as recommended.
It is important to note that this manual contains various CAUTIONS and NOTICES which should be carefully read in
order to minimize the risk of personal injury to service personnel. The possibility exists that improper service
methods may damage the equipment. It is also important to understand that these CAUTIONS and NOTICES ARE
NOT EXHAUSTIVE. AOC could not possibly know, evaluate and advise the service trade of all conceivable ways in
which service might be done or of the possible hazardous consequences of each way. Consequently, AOC has not
undertaken any such broad evaluation. Accordingly, a servicer who uses a service procedure or tool which is not
recommended by AOC must first satisfy himself thoroughly that neither his safety nor the safe operation of the
equipment will be jeopardized by the service method selected.
Hereafter throughout this manual, AOC Company will be referred to as AOC.
WARNING
Use of substitute replacement parts, which do not have the same, specified safety characteristics may create shock,
fire, or other hazards.
Under no circumstances should the original design be modified or altered without written permission from AOC.
AOC assumes no liability, express or implied, arising out of any unauthorized modification of design.
Servicer assumes all liability.
FOR PRODUCTS CONTAINING LASER:
DANGER-Invisible laser radiation when open AVOID DIRECT EXPOSURE TO BEAM.
CAUTION-Use of controls or adjustments or performance of procedures other than those specified herein may
result in hazardous radiation exposure.
CAUTION -The use of optical instruments with this product will increase eye hazard.
TO ENSURE THE CONTINUED RELIABILITY OF THIS PRODUCT, USE ONLY ORIGINAL MANUFACTURER'S
REPLACEMENT PARTS, WHICH ARE LISTED WITH THEIR PART NUMBERS IN THE PARTS LIST SECTION OF
THIS SERVICE MANUAL.
Take care during handling the LCD module with backlight unit
-Must mount the module using mounting holes arranged in four corners.
-Do not press on the panel, edge of the frame strongly or electric shock as this will result in damage to the screen.
-Do not scratch or press on the panel with any sharp objects, such as pencil or pen as this may result in damage to
the panel.
-Protect the module from the ESD as it may damage the electronic circuit (C-MOS).
-Make certain that treatment person’s body is grounded through wristband.
-Do not leave the module in high temperature and in areas of high humidity for a long time.
-Avoid contact with water as it may a short circuit within the module.
-If the surface of panel becomes dirty, please wipe it off with a soft material. (Cleaning with a dirty or rough cloth may
damage the panel.)

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1. General Specifications
Items Specification
LCD Panel
Screen Size 20” (50cm)
Driving system TFT-LCD Panel (CMO)
Resolution 1366(H)×768(V)
Display Area 444.633(H) x 249.984 (V)
Pixel Pitch 325.5um × 325.5um
Display colors 16.2 million
Contrast Ratio 1000:1 (Typical)
Brightness 500 cd/m2(Typical)
Viewing Angle 176(H)/176(V) (CR>20)
Response Time 8ms
Lamp Type/Life 60000 hr
TV Function
TV Standard PAL B/G, D/K, I, L/L’ and SECAM L/L’(Multi-Europe)
Full Channel with Electronic PLL Tuner
Sound Systems NICAM
Video Color systems PAL/SECAM/NTSC
Video Inputs SCART, S-Video, Composite, HDMI, Component
PC Input
Signal Input Analog: D-Sub 15 pin (detachable cable)
PnP compatibility DDC 2B
Input frequency Analog: FH: 31.5KHz to 48KHz FV: 56Hz to 75Hz
Input Audio Headphone Mini-jack for stereo (3.5ø)
Audio Output Audio Output: L / R
Speaker (built-in): 3 watt speakers x 2
Headphone Mini-jack for stereo (3.5ø)
Line Output (SCART L/R)
Other Function PIP (in PC Mode)
Table Stand Included
Wall Mount VESA 100 x 100 mm
Power Power Supply AC 220V~240V, 50/60Hz
Power Consumption <90 W
Environment
Operating temp + 0 °C ~ + 40 °C
Storage temp - 10 °C ~ + 50 °C
Operating humidity 10% ~ 85%

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2. Operating Instructions
2.1. The Use Of Remote Control

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2.2 To Use The Menus

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2.3 LCD TV Description
The LCD TV will contain a main board, a power board, an IR board, a key board, a tuner board and a
headphone Board. The main board and power board will house the flat panel to control logic I²C bus, DDC,
brightness control logic for LCD panel, DC-DC conversion to supply the appropriate power to the whole board
and transmitting TTL level signals into LCD Module to drive the LCD display circuit.
The inverter board will drive the CCFLs (Cold Cathode Fluorescent Tube).
The switching power board will provides the power ON/OFF to control the TV and control LED indicator for
DPMS.
The function keyboard and Remote Control will provide the OSD control signal to the Main Board.
2.4 Interface Connector
(A) Power Cord Connector.
(B) RF Signal Connector.
(C)Video / Audio Signal Connectors.
(D)PC D-sub 15 pin Connector.
(E) PC Audio Connector
(F) SCART Connector
(G)S-Video Connector
(H)Composite Connector
(I) Component Connector
(J) HDMI Connector

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3. White Balance, Luminance Adjustment
Instrument List:
Chroma 2225、VG848、Chroma 7120
Adjustment Process:
①Instrument Orientation
Connect LCD-TV、Chroma 2225 and VG848, and set Timing137、Pattern1 on Chroma2225. Chroma7120’s lens
must aim at the center of Pattern1 showed on the LCD-TV’s screen. The distance of Chroma7120’s lens and the
center of screen is 20cm±1cm.
②ENTER FACTORY
After orientation OK, set Pattern104(black picture) on Chroma225.Press 1-9-9-9 on remote to enter the menu
on top left of the screen(refer to fig.1,this menu will show slowly), then from UP key(△) option to enter the menu
(refer to fig.2).
Fig.1

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Fig.2
Fig.3
③PC Mode White Balance Adjustment
Begin to adjust the W/B (White Balance) you should select the Color Temp(Warm and Cold) and enter the son
menu from father menu “Scaler” refer to Fig.2 and Fig.3.
Set channel color temperature value and brightness on Chroma7120.Set 303 319 350(warm Temp) on CH3 and
278 289 350(cold Temp) on CH4.Press MODE key on Chroma7120 to switch xyY mode.
Use black sleeve on Chroma7120’s lens to ensure no external ray. Set Pattern104 on Chroma2225.Adjust
SCALAR RB、GB、BB value to make sure the brightness is the lowest, then set Pattern105 on Chroma2225 and
adjust RG、GG、BG value to make the value displaying on Chroma7120 is about 100.Press “Save” to save. Switch
to CH4, select cold Temp and then adjust it according to above method. Press “Save” to save.
④AV MODE W/B ADJUSTMENT
Begin to adjust AV/COMPONENT YPbPr(480I/576I)/COMPONENT T-scaler(480P/720P/1080I) /HDMI W/B,
their Color Temp modes refer to Fig.4/5/6/7
Fig.4

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Fig.5
Fig.6
Fig.7

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1.OFFSET(26%) W/B ADJUSTMENT(This is only for AV/TV)：Change the input signal to 26% white level
performance .Set the CHROMA7120 to 288 301 30 and MODE_RGB ,then adjust the TV’s RB、GB、BB to make
CHROMA7120 display to 100.
2.W/B ADJUSTMENT (100%): Change the input signal to 100% white level performance. Set the
CHROMA7120 to 288 301 415 and MODE_RGB , then adjust the TV’s RG、GG、BG to make CHROMA7120 display
to 100.
3.Save the adjustment. Then change the input signal to 26% white level performance. Set the CHROMA7120 to
MODE_RGB and CH3, check whether the color temperature was in SPEC (color spec is x±15;y±15;Y±15). In this
time, most of the TV is in SPEC, while the others should be adjusted twice or more to make its color temperature in
SPEC.
4.CHECK CUT OFF: Change the input signal to 0% white level performance. Firstly, press the “brightness” from
50% to 0% and make sure the Y is not changed. Secondly, change the input signal to 32 GRAYS performance and
make sure the grays is not connected at any position.( as the 5% level is between the first gray and the second gray.
5%=（1/32）*1.6。)
1.The white color temperature in PC Mode should be app.7200K(CIE1931: x=0.303, y=0.319，Y>350),
10300K(CIE1931 : x= 0.278, y= 0.289, Y>350 ).
2.The white color temperature in AV/TV Mode should be app. 8700K(CIE1931:x=0.288±15, Y=0.301±15,
Y>370). In this Mode,we should check the black balance,which level is 26% of the white level(1.0Vpp).
3. The white color temperature in HDTV/HDMI Mode should be app. 8700K(CIE1931:x=0.288±15, Y=0.301±15,
Y>370)
Those three channels should be factory preset and not be possible to be modified.
The measurement position is the center of the display(5) at brightness set to center and
Contrast set to max. . The tolerance of the color coordinates should be less than ± 0.015

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4. Input/Output Description
4.1 D-SUB Connector
This procedure gives you instructions for installing and using the LCD TV display.
1. Position the display on the desired operation and plug the power cord into a convenient AC outlet.
Three-wire power cord must be shielded and is provided as a safety precaution as it connects the chassis
and cabinet to the electrical conduct ground. If the AC outlet in your location does not have provisions for
the grounded type plug, the installer should attach the proper adapter to ensure a safe ground potential.
2. Connect the 15-pin color display shielded signal cable to your signal system device and lock both screws
on the connector to ensure firm grounding. The connector information is as follow:
1
6
11
15
5
10
15 - Pin Color Display Signal Cable
Pin No. Description Pin No. Description
1 Red Video 9 No Pin!
2 Green Video 10 Sync Ground
3 Blue Video 11 Not Used
4 Not Used 12 Serial Data for DDC
5 Ground 13 H-Sync.
6 Red Ground 14 V-Sync.
7 Green Ground 15 Serial Clock for DDC
8 Blue Ground
3. Apply power to the display by turning the power switch to the "ON" position and allow about ten seconds for
Panel warm-up. The Power-On indicator lights "GREEN" when the display is on.
4. With proper signals feed to the display, a pattern or data should appear on the screen, adjust the
brightness and contrast to the most pleasing display, or press auto-adjust to get the best picture-quality.
5. This TV (with PC function) has power saving function following the VESA DPMS. Be sure to connect the
signal cable to the PC.
6. If your TV requires service, it must be returned with the power cord.