AOC M20S651B Schematic

20” LCD TV Color Monitor AOC M20S651B

CAUTION: USE A SEPARATE ISOLATION TRANSFOMER FOR THIS UNIT WHEN SERVICING

6.2 Power Board……………… ………….....…...... . 28

6.3 Key Board….….........................................…….........29

6.4 Tuner Board...………...…...................................30

6.5 Earphone board……………………...……..………31

7. Block Diagram..……..……................….......................32

7.1 Main Board...............……..……...............................32

7.2 Power Board…...……..….…...….…..........................33

8. Schematic Diagram…….….….………………….......34

8.1 Main Board……... …..……….………......................34

8.2 Power Board...……………….……………………...46

8.3 Key Board……………..…………..………………...49

8.4 Tuner Board.....…..........……………........................50

8.5 IR Board...…….........…………...............................54

9. Exploded View…….........………..............…................55

10. BOM List…………………… …….....…………………57

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

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

Im p ortant Safety Notic e .……...... ......... ...…… .... ..3

1. Monitor Specification..…............................………........4

2. Operating Instructions……...……………….……….......5

2.1 The Use Of Remote Control..…………..................5

2.2 Front Panel Control Knobs.....................…...........7

2.3 OSD Operating…………….…............……...............8

2.4 How To Connect...………........................…............12

3. Input/Output Specification............……………............14

3.1 Input Signal Connector............………….................14

3.2 Factory Preset Display Modes........………...............14

4. Mechanical Instructions..………....……......................16

5. Repair Flow Chart…….……………………..................20

6. PCB Layout………...……….……………....….…….....26

6.1 Main Board……...……………..……………....….......26

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 VOLTAGES.

1

Horizontal frequency

31.5 kHz to 48 kHz

20” LCD TV Color Monitor AOC M20S651B

Version

Release Date

Revision History

TPV Model

A00

Nov-08-2006

Initial Release

E206CHNBD1ACNP

Revision List

2

20” LCD TV Color Monitor AOC M20S651B

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.)

3

20” LCD TV Color Monitor AOC M20S651B

Item

Spec

LCD Panel

Screen Size

20” TFT-LCD Panel

Aspect Ratio

4 : 3

Resolution

640 x480 (XGA)

Display Area (opening) H x V

408mm x 306mm

Pixel Pitch

0.6375mm x 0.6375mm

Display Colors

16.2 million

Contrast Ratio

500:1

Brightness

450 cd/m2

Response Time

12ms

Viewing angel

160° H/ 160°V

Lamp Type/Life

50000 hr

Color Temperature

Cold / Warm/Normal

VGA Function
Input support definition

640*480 /60Hz

Audio input

Mini jack for stereo headphones (3.5ø)

TV Function
TV Standard

SECAM PAL

Color systems

SECAM L/L’ PAL BG/DK/I

Sound System

Mono, Nicam stereo, A2

Video Input
AV

RCA x 1

Audio L/R x 1
S-VIDEO

S-Videox 1

SCART

CVBS/RGB

Audio output

Audio output: L / R
Speaker (built-in): Two 2 watt speakers

Headphone Mini-jack for stereo (3.5ø)

OSD Language

English，France，Deutsch，Spanish，Portugese，Polish, Russian，Italian，Finnish，
Swedish

Table Stand

Yes

Wall Mount

VESA 100 x 100 mm

Power
Power

AC100V-240V, 50/60Hz

Power Consumption

<70W

Panel Tilt

Forwards/Backwards/
Rotation

-4°/ +18° / ± 35°

Environment

Temperature

+ 0 °C ~ + 40 °C

storage

- 25 °C ~ + 60 °C

operating

10% ~ 85%

Dimension

W x H x D (with stand)

498 x 495 x 185 (mm)

Net weight

Without accessory

9.5 Kg

1. General Specifications

2. Operations Instructions

4

20” LCD TV Color Monitor AOC M20S651B

MENU

Press this key to
display or exit main
menu.

Size

Size is not available
on this model.

SLEEP

With this key you can
set a time period
after which the TV
should switch itself to
standby. Press the
key repeatedly to
select the number of
minutes. The counter
runs from 0 to 120
minutes. The timer
begins to count
down from the
number of minutes
selected after the
display has
disappeared.

POWER:

Press to turn on/off
the TV. The TV is
never completely
powered off unless
it is physically
unplugged.

TV/VIDEO

Select your input
source: press
repeatedly to select

TV, AV, S-VIDEO or
SCART mode,

according to where
you connected your
external source.

PIP/POP
PIP/POP is not

available on this
model.

MUTE

Temporarily
interrupt the sound
or restore it.

SUBPAGE

Teletext Sub-page
function.

0~9 DIGIT

BUTTONS

To select a TV
channel.

CH

Press or (or
MENU ▲ or ▼
button) buttons to
scroll through the
channels.
VOL
Press + or – (or
MENU or
button) to increase
or decrease the
volume.

PRE-CH

To display the
previously selected
TV channel.

SOUND

To select Mono/
Stereo /Dual from TV
RF input.

DISPLAY

Press this key to

display:

(1) the channel

number when
watching a TV
program.

(2) the input source

when watching
the other video

SWAP

SWAP is not
available on this
model.

2.1 The Use of Remote Control

Teletext function and buttons will be described on next page.

5

20” LCD TV Color Monitor AOC M20S651B

TELETEXT

Press TELETEXT. The Teletext screen
appears.
To turn off the Teletext mode, press

TELETEXT again.

MIX

Press MIX to superimpose the teletext over
a normal broadcast picture. Press again to
return to Teletext mode.

SIZE
Press SIZE repeatedly to display the upper
teletext part, the lower teletext part and
then to return to the normal.

RED / GREEN / YELLOW / BLUE

Use the COLOURED BUTTONS to operate
the Teletext screen.

INDEX
Press INDEX to return to the main index page.

SUBTITLE
Press to select the next page marked as a
subtitle page and request it as the display
page.

HOLD
Press HOLD to hold the Teletext page when
viewing information. Press again to return to
automatic page update.

REVEAL
Press REVEAL to display reveal hidden
words e.g. quiz page answers. Press again
to hide.

PAGE SELECTION
Page can be selected in two ways.
a. Press ▼or ▲ to increase or decrease the page number by one.
b. By entering the page number, using digit buttons 0~9.

TELETEXT

Teletext is an information service organized like a magazine, which is provided by some TV stations in addition to
regular television broadcasting.

6

20” LCD TV Color Monitor AOC M20S651B

2.2 Front Panel Control Knobs

Power Key ⑦ : Press to turn on or off the TV.
MENU Key ⑥ : Press to show the OSD menu and exit OSD menu at the TV.
CH Down / Up Key ⑤ ④: Select the intended function by pressing these two keys, or switch the channels in the

TV mode.

Vol + /- Key ② ③: Press to confirm your function selection and adjustment volume.
Source Key ① : Press to select your input source.

Lay the LCD TV with the screen down on a table, as it will be easier to connect your peripheral equipment. Please
take your precautions not to damage the screen.

1: AC power input terminal
2: VGA input
3: VGA audio input
4: AC main switch
5: Headphone outlet
6: SCART signal input
7: Left video/audio track input
8: AV1 signal input
9: Right video/audio track input
10: S-Video signal input
11: TV signal input

7

20” LCD TV Color Monitor AOC M20S651B

2.3 OSD Operations

1. Press the MENU button to display or close main menu.

2. Use the cursor up/down to select a menu item.

3. Use the cursor left/right to enter a submenu or enable/disable the function.

4. Press the MENU button to exit the menu.

Main Menu

Press the MENU button to enter the main OSD (On Screen Display). Adjust the items including Picture Setup,
Sound setup, Function Setup and TV setup. When the input source is PC/AV1/AV2 (SCART)/S-VIDEO mode, only
the Sound Setup, Picture Setup and Function Setup can be selected; shown in the figure below:

When the input source is TV mode, the Sound Setup, Picture Setup, Channel select Setup, Function Setup and TV
Setup can be selected; shown in the figure below:

Sound Setup (Same as in PC, TV, AV1, S-Video and AV2(SCART))

1. The range of adjusting volume, bass and treble is from 0~100.

2. Select “ON” or “OFF” in sound selection to control the sound output.

3. Bass and Treble: the easy Equalizer function, Bass can adjust the low frequency sound and Treble can adjust
the high frequency sound.

4. The range of adjusting Balance is -50~+50; when adjusting from 0 to -50, the sound from the left track fades
until silence; when adjusting from 0 to +50, the sound from the right track fades until silence.

5. AVL: you can set it “ON” or “OFF”.

The function is to adjust the input sound automatically. You may enable this function when you notice that the
sound in the two tracks are very different, in order to prevent the bad sound effect resulting from large sound
variation.

6. Select "ON" or "OFF" for Loudness: a default setting is preset, you may adjust when necessary.

The following menu will appear when selecting continuously:

8

20” LCD TV Color Monitor AOC M20S651B

7. Preset: Designed for different types of sound output, wherein, the voice music personal and theater modes are
preset; you can set Bass, Treble and Equalizer in sound output mode according to your preference.

8. Equalizer: You can select and adjust 100, 300, 1K, 3K and 8K respectively (the figures represent the sound
frequency range).

9. Reset to default: Reset the sound setting to the factory default value.

Picture Setting

When the input source is in PC mode, you can select Brightness, Contrast, Position, Video noise, Sharpness, Auto
Adjust, Info, Color Temp., Red, Green, Blue and Reset to default; shown in the figure below:

1. Brightness and Contrast: The range can be adjusted from 0~100.

2. Position: There are two options, Horizontal and Vertical, which can be adjusted from -50 to +50.

3. Video noise: There are two options, Phase and Clock, which can be adjusted from -50 to +50.

4. Sharpness: Select from five options of Softest, Soft, Auto, Sharp and Sharpest. You may adjust the above
options according to your preference.

5. Auto Adjust: Automatically adjust PC input to the optimal screen size.

6. Info: Prompt the current size for PC input definition (only the definition that can be shown by this device).

7. Color Temp.: There are four options of color temperature provided for users - normal, warm, cold and
Personal. You can select the three color temperatures of normal, warm, and cold, or manually adjust red, green
or blue in the personal setting (you can only adjust red, green and blue in the user setting).

8. Reset to default: It is used to reset the picture settings to the factory default mode.

When the input source is in TV/AV1/S-Video/ AV2(SCART), you can select Brightness, Contrast, Colour,
Sharpness, Dyn. skin tone, White Tone, preset and Reset to default respectively; shown in the figure below:

9

20” LCD TV Color Monitor AOC M20S651B

Function Setup

When the input source is in TV, AV1，AV2 or S-Video mode, you can select Source OSD, Language, Country, ACI
Timers，Teletext lang./ Teletext E/W and Reset to default; shown in the figure below:

1. Current Source OSD setting: When OSD is set to ON, the left upper corner of the display will show the input
source or the TV channel number; when OSD is set to OFF, the input source or the TV channel number will
disappear.

2. OSD language setting: There are ten language options provided - English, France, Deutsch, Spanish,
Portugese, Polish, Russian, Italian, Finnish, Swedish.

3. Timers

(1).Sleep Timer: Set the sleeping timer and the alert function which indicates the time left.
(2). Reminder timer: set the Reminder timer function which give the user a warning

4. Teletext lang. and Teletext E/W：the user can set the teletext language

5. Reset: It is used to reset the OSD settings.

When the input source is in PC mode, you can select Source OSD, Language, Timers and Reset to default; shown
in the figure below:

Source OSD, Language, Timers and Reset to default options are operated similarly as the above instructions!
When the input source is in TV mode, you can select the difference function.

10

20” LCD TV Color Monitor AOC M20S651B

Country and ACI function：the user can select Country and if the program system has ACI （Auto Channel
Installation）function

TV Setting

The following menu appears only in the TV mode.
A. channel select function
This set can give the user a channel list that all channel received

B. channel setup function

1. Program nr: Shows the current program number.

2. Program name：show the program name, also the user can give the program a unique name

3. Colour System / sound system: select the colour and sound system the current channel.you can selet ”auto”,the
set will identify it by oneself

4. Auto search: Select "Auto Search" to search all signaled channel; when the searching is complete, it stays at the
first channel with signal and all channels that have been located are stored. If you would like to stop "Auto
Search" during the process, simply by pressing the function button.

5. Frequency：show the current signal Frequency

6. AFC can be set to ON or OFF. When it is set to ON, the TV will search the TV signal automatically; when there is
any offset in the signal, it will automatically adjust the channel to the correct position.

7. Reset to default: Reset to the factory default value.

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20” LCD TV Color Monitor AOC M20S651B

2.4 How To Connect

VIDEO RECORDER

VIDEO RECORDER

1. Connect the antenna cable to the RF IN port of your VCR.

2. Connect another FR cable from the port of your VCR to the antenna port of you TV set. If you have connected

the video/audio cable to the video AV port, you may have better sound and picture when playing the VCR .

If your VCR has an S-VHS video jack:

For improved picture quality, connect a S-Video cable with the S-VIDEO input on the TV.
S-Video does not provide audio, audio cables must still be connected to provide sound(AV and S terminal share one
audio input).

Watching VCR

1. If you use connection TV, select the TV channel auto search.

2. If you use connection AV, select video AV input.

3. Insert videotape in the VCR and press the PLAY button.

How to connect

1. The SCART socket can be connected a VCR, a camcorder, a DVD player, a satellite receiver, a decoder or a

game console form SCART cable.

2. The 21pin SCART socket can also be used as an output to Audio/Video equipment.

How to use

Scart source has the first priority. For example: when playing under other sources such as TV/AV/S-VIDEO/PC, if we
input the scart signal, the TV will switch to Scart menu automatically.

How to connect

1. Connect the camera, camcorder and game set to the ports of the audio/video set.

2. The camcorder may get better picture by connecting a S-VHS cable between the S terminal and the Audio set.

How to use it

1. Select the video AV or S terminal input.

2. Enable the exterior AV equipment.

Warning: In case you notice scrolling images, wrong colors or no color, no picture or even combinations of these, on
your screen, check if the connections are done in the right way. Check if the cable colors match with the Input
connector colors.

12

20” LCD TV Color Monitor AOC M20S651B

WALL MOUNT

Use of Wall Mount Bracket:

1. Remove the hinger cover.

2. Remove the four units M4.0 screws.

3. Remove the base ass’y.

4. Fasten four units M4.0 X 10mm screws to secure the wall mount bracket.

1. The headphone jack is located at the side of the TV.

2. The MUTE key on the remote control works on both internal speaker and the headphone.

3. Use volume key to adjust the volume.

Care of the screen

Do not rub or strike the screen with anything hard as this may scratch, mar, or damage the screen permanently.
Unplug the power socket before cleaning the screen. Dust the TV by wiping the screen and the cabinet with a soft,
clean cloth. If the screen requires additional cleaning, use a clean, damp cloth. Do not use liquid cleaners or aerosol
cleaners.

Mobile telephone warning

To avoid disturbances in picture and sound, malfunctioning of your TV or even damage to the TV, keep away your
mobile telephone from the TV.

End of life directives

We are paying a lot of attention to produce environmentally friendly in green focal areas. Your new receiver contains
materials which can be recycled and reused.
At the end of its life specialized companies can dismantle the discarded receiver to concentrate the reusable
materials and to minimize the amount of materials to be disposed of.
Please ensure you dispose of your old receiver according to local regulations.

13

20” LCD TV Color Monitor AOC M20S651B

1611

15

5

10

Pin

Signal Assignment

Pin

Signal Assignment

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

Horizontal Sync.

6

Red Video Ground

14

Vertical Sync.

7

Green Video Ground

15

Serial Clock for DDC

8

Blue Video Ground

3. Input/Output Specification

3.1 Input Signal connector

This procedure gives you instructions for installing and using the LCD TV display.
Lay 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.

Connect the 15-pin D-SUB 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

14

20” LCD TV Color Monitor AOC M20S651B

Timing

Resolution

H/V

frequency

Remark

T115

640*480

31k/70Hz

can show this timing, but it is out of range actually

T116

640*480

31K/60Hz

can show this timing.

T117

640*480

37K/75Hz

Can not display this timing, show “out of range”

T118

640*480

37K/72Hz

can show this timing, but it is out of range actually

T119

640*480

43K/85Hz

Can not display this timing, show “out of range”

T126

800*600

37.8K/60Hz

can show this timing, but it is out of range actually

T127

800*600

46K/75Hz

Can not display this timing, show “out of range”

T128

800*600

48K/72Hz

can show this timing, but it is out of range actually

T129

800*600

53K/85Hz

Can not display this timing, show “out of range”

T137

1024*768

48K/60Hz

can show this timing, but it is out of range actually

T138

1024*768

56K/70Hz

can show this timing, but it is out of range actually

T139

1024*768

60K/75Hz

Can not display this timing, show “out of range”

T140

1024*768

69K/85Hz

Can not display this timing, show “out of range”

T144

1280*1024

63K/60Hz

can show this timing, but it is out of range actually

T148

1280*1024

80K/75Hz

Can not display this timing, show “out of range”

3.2 Factory Preset Display Modes

Analog RGB input signal timing

15

20” LCD TV Color Monitor AOC M20S651B

Step

Figure

Description

Preparation
and
remove
the base

Remove the
screws
remarked in red

Remove
back cover

Remove the
screws
remarked in red

4. Mechanical Instructions

16

20” LCD TV Color Monitor AOC M20S651B

Remove
shield

Remove the
screws
remarked in red

17

20” LCD TV Color Monitor AOC M20S651B

Remove
the boards
and main
frame

Remove
connectors and
the screws
remarked in red

18

20” LCD TV Color Monitor AOC M20S651B

Remove
the panel

Remove the
screws
remarked in red

The end

19

20” LCD TV Color Monitor AOC M20S651B

Check the source

Reset source

Check LVDS cable

NG

Replace LVDS cable

Check 12V power supply

Return to “5.3”

Check U406

Replace U406

Check panel

Replace panel

Check main board power supply

Check I2C communication

Repair I2C communication relative circuit

No display

OK

NG

OK

NG

OK

OK

NG

OK

NG

OK

NG

5. Repair Flow Chart

5.1. No Display (LED indicator green)

20

20” LCD TV Color Monitor AOC M20S651B

NG

Repair the keyboard

Check 5V_SB

Check every chip power supply

Check I2C communication

Check keyboard

Replace I2C communication component

Check oscillistor

Replace oscillistor

Can’t start

OK

OK

NG

NG

OK

NG

5.2. Can’t start (LED indicator yellow)

21

20” LCD TV Color Monitor AOC M20S651B

No Power

Check power
cord and board
interface

NO

Plug in power cord and interface

OK

Check F901, BD901

NG

Replace F901 or BD901
OK

Check the load

Check IC901, Q901
NG

Replace IC901 or Q901

OK

Check T901

NG

Replace T901

OK

Check D904, D905

Replace D904, D905

NG

OK

Replace Q903, ZD902, IC903 IC902

Check Q903, ZD902, IC903，IC902 and
relative circuit

NG

OK

Check Q906, IC905 and relative circuit

5.3. No Power (No LED indicator)

22

20” LCD TV Color Monitor AOC M20S651B

Check the source

OK

Reset source

Check signal filter circuit

Replace the filter or inductance

Repair each relative circuit

Check TU601

Replace TU601

AV, S-video signal
component PC signal

Check LVDS cable

Replace LVDS cable

Replace panel

Abnormal display

NG

NG

OK

NG

OK

RF signal

NG

OK

OK

OK

NG

Check panel

NG

OK

OK

Check TV system setup

Check input signal

5.4. Abnormal Display

23

20” LCD TV Color Monitor AOC M20S651B

Check the source

Reset source

Check signal filter circuit

NG

Replace the filter or inductance

Check TU601

Replace TU601

AV, component, S-video, PC signal

Check Amplifier TDA7266D U601

Replace U601

Check Earphone jack

Replace the Earphone jack

Check speakers

Replace speakers

Check relative circuit

No sound

OK

NG

OK

NG

OK

NG

OK

OK

NG

NG

OK

NG

OK

NG

Check TV system setup

SIF signal

5.5. No Sound

24