AOC N20W451T Schematic

20” LCD TV AOC N20W451T

Table Of Contents.......……..............................…........1

Revision List.….... ....................................……......2

Im portan t Safety Notic e .……........ . .........……... . ..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

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

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20” LCD TV AOC N20W451T

Revision

Date

Revision History

TPV Model

A00

Jan-18-07

First Version Release

EAF5MTNBC2TETMP

Revision List

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20” LCD TV AOC N20W451T

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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20” LCD TV AOC N20W451T

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%

1. General Specifications

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20” LCD TV AOC N20W451T

2. Operating Instructions

2.1. The Use Of Remote Control

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

2.2 To Use The Menus

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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20” LCD TV AOC N20W451T

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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20” LCD TV AOC N20W451T

3. White Balance, Luminance Adjustment

Instrument List:

Chroma 2225、VG848、Chroma 7120
Adjustment Process:
① Instrument 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.
② ENTER 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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20” LCD TV AOC N20W451T

Fig.2

Fig.3

③ PC 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.
④ AV 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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20” LCD TV AOC N20W451T

Fig.5

Fig.6

Fig.7

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20” LCD TV AOC N20W451T

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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20” LCD TV AOC N20W451T

1611

15

5

10

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

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:

15 - Pin Color Display Signal Cable

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.

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20” LCD TV AOC N20W451T

Dots × Lines

Horizontal

Vertical

Sync Polarity

Presence

Screen Mode

Frequency

(kHz)

Frequency

(Hz)

Horizontal

Vertical

Horizontal

Vertical

Normal

(4:3)

FULL
(16:9)

720×400

31.47

70.08

NEG

POS

YES

YES

YES

YES

640×480

31.50

60.00

NEG

NEG

YES

YES

YES

YES

640×480

37.50

75.00

NEG

NEG

YES

YES

YES

YES

640×480

37.86

72.81

NEG

NEG

YES

YES

YES

YES

800×600

37.90

60.32

NEG

NEG

YES

YES

YES

YES

800×600

46.90

75.00

NEG

NEG

YES

YES

YES

YES

800×600

48.08

72.19

NEG

NEG

YES

YES

YES

YES

1024×768

48.40

60.00

YES

YES

YES

YES

YES

YES

1280×768

47.7

60

YES

YES

YES

YES

YES

YES

4.2 Factory Preset Display Modes:

Analog RGB Signal Timing

5. Front Panel Control Knobs

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20” LCD TV AOC N20W451T

NG

Check power cord and board interface

Plug in power cord and interface

OK

Check F901, BD901, D910

NG

Replace F901 or BD901 or D910

OK

Check IC930, Q930 (VCC1)

Check D970, D980

NG

Replace IC930 or Q930

Check Q931, ZD930 (VCC2)

NG

Replace Q931 or ZD930

OK

OK

Check T901

OK

NG

Replace T901

Replace D970 or D980

OK

Check F970 (12V), F980 (24V)

Check PC950, TL950 (FB)

Replace PC950 or TL950

OK

NG

NG

NG

Replace F970 or F980

Check the load

OK

Check IC 960

NG

Replace IC 960

OK

Check Q961, Q962

Replace Q961 or Q962

NG

OK

Check Q960

NG

Replace Q960

Check F960

NG

Replace F960

OK

Check the load

Check the load

6. Repair Flow Chart

6.1 No Power (No LED indicator)

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20” LCD TV AOC N20W451T

NG

Repair the keyboard

OK

Check 5V_SB

NG

Return to “6.1”

Check 3.3V_SB

Replace U703 or F702

OK

NG

Check PWR_ON signal

OK

NG

Check Q703, Q708, Q704

NG

Replace Q703 or Q708 or Q704

Check U402, U403

NG

Replace U402 or U403

Check I2C communication

OK

Check Q940 (VCC3)

NG

Replace Q940

OK

Check main board power supply

Check keyboard

NG

Replace panel

Check Panel inverter board

6.2 Can not start (LED indicator yellow)

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20” LCD TV AOC N20W451T

Check the source

OK

Reset source

NG

Check LVDS cable

NG

Reset LVDS cable

OK

Check 24V power supply

NG

Return to “6.1”

OK

Check main board power supply

OK

Check U401

NG

Replace U401

OK

Check I2C communication

OK

Check panel

NG

Replace panel

6.3 No Display (LED indicator green)

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20” LCD TV AOC N20W451T

Check the source

OK

Reset source

NG

Check signal filter circuit

NG

Replace the filter or inductance

OK

Check U106

NG

Replace U106

RF signal

Check TV system setup

OK

Check TU101

Replace TU101

AV, SCART1/2_CVBS signal

OK

NG

Check U107

NG

Replace U107

S-video SCART2_Y/C signal

Check U104

NG

Replace U104

PC signal

Check U102

NG

Replace U102

OK

Check U401, U407

NG

Replace U401

6.4 Abnormal Display

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20” LCD TV AOC N20W451T

Check the source

OK

Reset source

Check signal filter circuit

NG

Replace the filter or inductance

OK

NG

SIF signal

Check TV system setup

OK

Check TU101

Replace TU101

AV, AIR1/AIR2, PC signal

Check Audio decoder MSP3410G U602

NG

Replace U602

OK

Check U603

NG

Replace U603

OK

NG

Replace U602

Check Earphone jack

NG

Replace the Earphone jack

OK

Check speaker

NG

Replace speaker

Check Amplifier MAX9714ETJ U602

6.5 No sound

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20” LCD TV AOC N20W451T

OSD is unstable or not working

Is Key Pad Board connecting normally?

Connect Key Pad Board

Is Button Switch normally?

Replace Button Switch

Y

Is Key Pad Board Normally?

Replace Key Pad Board

Check Main Board

N N Y Y N

Key Board

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20” LCD TV AOC N20W451T

Step

Figure

Description

Preparation

Lay the
LCD-TV on a
flat, soft and
clean surface.

Remove

the stand.

Remove the
screws
remarked on
red to remove
the stand.

Remove
the back
cover

Remove the
screws marked
in red to
remove the
back cover.

7. Mechanical Instructions

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