Norcent LT2025W User manual

20” LCD TV Color Monitor Norcent LT2025W
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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 VOLTAGES.
CAUTION: USE A SEPARATE ISOLATION TRANSFOMER FOR THIS UNIT WHEN SERVICING
6.2 Power Board………………………….....….......29
6.3 Key Board….…..........................…….........30
6.4 Tuner Board...………...…...................................30
7. Block Diagram..……..……................….......................31
7.1 Main Board...............……..……...............................31
7.2 Power Board…...……..….…...….…..........................32
8. Schematic Diagram…….….….………………….......33
8.1 Main Board……...…..……….………......................33
8.2 Power Board...……………….……………………...46
8.3 Key Board……………..…………..………………...47
8.4 Tuner Board.....…..........……………........................48
8.5 IR Board...…….........…………...............................52
8.6 Earphone Board...…….........………................……...53
9. Exploded View…….........………..............…................54
10. BOM List…………………… …….....……….…..........55
Table Of Contents.......…….…..............................…........1
Revision List.…….….....................................……......2
Important Safety Notice.……..................……......3
1. Monitor Specification..…............................………........4
2. Operating Instructions……...……………….……….......6
2.1 The Use Of Remote Control..…………..................6
2.2 Front Panel Control Knobs.....................…...........6
2.3 OSD Operating…………….…............……...............8
2.4 How To Connect...………........................…............13
3. Input/Output Specification............……………............17
3.1 Input Signal Connector............………….................17
3.2 Factory Preset Display Modes........………...............17
4. Mechanical Instructions..………....……......................18
5. Repair Flow Chart…….……………………..................21
6. PCB Layout………...……….……………....….…….....27
6.1 Main Board……...……………..……………....….......27

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Revision List
Version Release Date Revision History TPV Model
A00 Sep-22-2006 Initial Release E206MHNKD4NCNCP
A01 Nov-07-2006 Add TPV Model in item 10 E206AHNKD4NONCP

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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
Item Spec
Screen Size 20” TFT-LCD Panel
Aspect Ratio 16 : 9
Resolution 1360 x768 (WXGA)
Display Area (opening) H x V 443.61(H) x 249.41(V) mm
Pixel Pitch 0.325 x 0.325 mm
Display Colors 16.2M
Contrast Ratio 500:1
Brightness 450 cd/㎡
Viewing angle (160° H/ 140° V )
Response Time 8ms
LCD Panel
Lamp Life 50000 hrs
Input support definition
Could support to 1360*768
This product could only support to 60Hz, ‘Input out of range’ will
be displayed when the input vertical frequency out of 60Hz
PC function
Audio input Mini jack 3.5ø stereo
TV Standard NTSC M
Sound System BTSC
TV
Function
Color systems NTSC
Video AV RCA x 1
S-VIDEO S-Video x 1
Audio L/R x 1
YPbPr YPbPr x 1 Audio L/R x 1
Video Input
YPbPr support modes 480i, 480p, 720p, 1080i

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Speaker (built-in): Two 3 watt speakers
Audio output Audio output: L / R
Headphone Mini-jack for stereo (3.5ø)
OSD Language
English, French, German, Spanish, Portuguese and Traditional Chinese.
Base Stand Yes
Wall Mount Standard VESA 100 x 100 mm
Power AC100V-240V, 50/60Hz
Power Consumption
< 90W
Power
Standby Power < 1.1W
Panel Tilt Forwards/Backwards/
Rotation fixed
Operating Temperature + 5 °C ~ + 35 °C
Storage Temperature - 10 °C ~ + 60 °C
Environment
Operating Humidity 10% ~ 85%
Dimension W x H x D (with stand) 546mm X445mmX185mm
Net weight 7.5 Kg (Without accessory)
Accessory Remote control, Batteries (AAAx2), Power cord, VGA Cable, Audio Line Cable, User
Manual

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2. Operations Instructions
2.1 The Use of Remote Control
Open the back battery cover of the remote control and install two AAA size
batteries and then close the battery cover on to the remote control.
MUTE
Temporarily interrupt the sound o
r
restore it.
DISPLAY
Press this button to display Channel.
MTS /SAP
Press this key to activate Multichannel
Television Sound, Stereo, SAP or Mono
sound.
PRE-CH
To display the previously selected T
V
channel.
TV/VIDEO
Select your input source: press
repeatedly to select source.
CAPTION
Press this button to select Closed
Caption mode (off, CC1~4, TXT 1~4).
SWAP
Not Supported.
SIZE
Press this button to adjust the picture
size, Auto , FullScreen, WideScreen o
r
4:3
POWER
Power on/Off.
0~9/100 Digit buttons
To select a TV channel.
CH
Press¿or Àto adjust channel.
VOL
Press + or - to adjust the volume.
PC
To change to PC input mode.
SLEEP
To set sleep timer.
PIP
Not Supported.
MENU
Press repeatedly to display or exit
OSD menu.
V-CHIP
Press this button to setup parental
control (active after child lock OSD
manual is set to ON).
POP
Not Supported.

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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 ⑤④:Select the intended function by pressing these two keys, or switch the channels in the
TV mode.
Vol + /- Key ②③: Press to confirm your function selection and adjustment
volume.
Source Key ①: Press to select your input source.

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2.3 OSD Operations
1. Press the MENU button to display each menu.
2. Use the cursor up/down buttons to select a menu item.
3. Use the cursor left/right buttons to enter a submenu or enable/disable the function.
4. Press the MENU button to exit the menu.
Press the MENU button to enter the main OSD (On Screen Display). Adjust the items including Picture Setup,
Sound setup, Child Lock Setup, Function Setup and TV setup. When the input source is PC or Component mode,
only the Sound Setup, Picture Setup and Function Setup can be selected; shown in the figure below:
When the input source is AV or S-Video mode, the Sound Setup, Picture Setup, Child Lock Setup and Function
Setup can be selected; shown in the figure below:
When the input source is TV mode, the Sound Setup, Picture Setup, Child Lock Setup, Function Setup and TV
Setup can be selected; shown in the figure below:
Sound Setup (Same as in PC, TV, AV, S-Video and Component modes)
1. The range of adjusting volume, bass and treble is from 0~100.
2. Select “ON” or “OFF” in Audio selection to control the sound output.
3. The range of adjusting Balance is -50~+50; when adjusting from 0 to -50, the sound from the right track fades
until silence; when adjusting from 0 to +50, the sound from the left track fades until silence.
4. 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.
5. Select "ON" or "OFF" for Loudness: a default setting is preset, you may adjust when necessary.
The following menu will appear when selecting continuously:
6. Preset: Designed for different types of sound output, wherein, the Voice, music and theater modes are preset;
you can set Bass, Treble and Equalizer in sound output mode according to your preference.
7. Equalizer: You can select and adjust 100, 300, 1K, 3K and 8K respectively (the figures represent the sound
frequency range).
8. Reset to default: Reset the sound setting to the factory default value.
Picture Setting

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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 options of Auto Softest, Soft, Normal, Sharp and Sharpest. You may adjust the above
options according to your preference.
5. Auto Adjust: Automatically adjust PC input to the optimal screeen 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 - Warm, Normal, Cool and User.
You can select the three Color temperatures of Warm, Normal, and Cool, or manually adjust red, green or blue
in the User 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/AV/S-Video mode, you can select Brightness, Contrast, Color, Sharpness, Tint,
Dyn. skin tone, Color Temp., Zoom and Reset to default respectively; shown in the figure below:
When the input source is in Component mode, you can select Brightness, Contrast, Video noice, Color,
Sharpness, Tint, Color Temp, Zoom and Reset to default respectively; shown in the figure below:

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1. Brightness and Contrast: The range can be adjusted from 0~100; use Brightness and Contrast options to adjust
the brightness and contrast of picture.
2. Video noise: There are two options, Phase and Clock, which can be adjusted from -50 to +50.
3. Color: The range can be adjusted from 0~100; use this option to adjust the Color saturation of picture.
4. Sharpness: Select from options of Auto, Softest, Soft, Normal, Sharp and Sharpest. You can adjust the
sharpness of picture using any option above.
5. Tint: The range can be adjusted from -50~+50; use this option to adjust the Color tone of picture.
6. Color Temp.: There are three options of Color temperature provided for users - warm, normal and cool.
7. Zoom: There are various functions provided for zoom in/zoom out.
8. Reset: It is used to reset the picture settings to the factory default mode.
Function Setup
When the input source is in TV, AV or S-Video mode, you can select Source OSD, Language, Child lock, Timers, CC
Mode 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 six language options provided - English, French, German, Spanish,
Portuguese and Traditional Chinese.
3. Child Lock Setup;
(1). You can enter the V-Chip level setting only when the Child Lock is ON, and the V-Chip will be enabled; you can
not enter V-Chip level setting when the Child Lock Setup is OFF, and the V-Chip is disabled.
(2). Lock code: V-Chip password can be set up when the code is locked. Enter the 4-digit password which you
choose! The factory default password is 0000.
4. Sleep Timer: Set the sleeping timer and the alert function which indicates the time left.
5. Closed Caption (CC) setting: Select CC1~CC4, TXT1~TXT4 or OFF.
6. Reset: It is used to reset the OSD settings.

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When the input source is in PC or Component mode, you can select Source OSD, Language, Sleep Timer and
Reset to default; shown in the figure below:
Source OSD, Language, Sleep timer and Reset to default options are operated similarly as the above instructions!
Child Lock
When the input source is in TV, AV or S-Video mode, V-Chip level can be set. You can enter the Child Lock setting
only when the Child Lock is ON. When you enter the Child Lock setting, a message on the display will prompt you to
enter password:
You can enter the Child Lock setting to set up the V-Chip level when you enter the correct password:
1. Age: it may be set to Child, Youth, Young adult, Adult, Custom or OFF; when you select Custom, it can be set
according to you preference.
2. MPAA Rating: Select the movie ratings from low to high (alert) - G, PG, PG-13, R, NC-17, X and off.
3. PG Rating: Shown in the figure below:
The empty box refers to unlocked; the solid box refers to locked.
TV Setting
The following menu appears only in the TV mode.

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1. Channel nr: Shows the current channel number.
2. Tuning mode: Select the mode of TV signal - Cable\HRC Cable\IRC Cable\ Broadcast.
3. System standard: NTSC-M , Auto
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 MENU button.
5. Fine tune: NTSC-M is seldom used.
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 positon.
7. Skip can be set to ON or OFF. When it is set to ON, a channel can be skipped when pressing the CH button on
the remote control or on the front panel.
8. Reset to default: Reset to the factory default value.

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2.4 How To Connect
2. Connect another RF cable from the output RF of your VCR to the Antenna input of your TV. Better quality
when playing from your VCR can be obtained if you also connect the Video, Audio LEFT AND RIGHT (only for
stereo equipment) cables to the VIDEO, AUDIO L and Rinputs AV.
If you are using only mono equipment, connect only the VIDEO and the AUDIO L (Mono) ports.
If your VCR has an S-VHS video jack:
For improved picture quality, connect an S-Video cable to the S-VIDEO input on the TV instead of connecting the
VCR to the VIDEO port of AV.
S-Video does not provide audio, audio cables must still be connected to provide sound. (S-Video and AV share the
same audio input port)
Watching VCR
1. If you use connection , select the TV channel 3 or 4.
2. If you use connection , select VIDEO or S-VIDEO, (see P7 TV/ VIDEO)
3. Insert videotape in the VCR and press the PLAY button.
1. Connect the antenna
cable to the RF IN
port of your VCR.

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1. Connect the three
separate component
video cables to
the DVD player’s.
Y, Pb and Pr ports
and to the Y, Pb and
Pr ports on the TV.
2. S-Video Connection
S-VHS quality with an S-VHS camcorder is obtained by connecting the S-VHS cable to the S-VIDEO input
and AUDIO input .
How to use
1. Select VIDEO or S-VIDEO input source (see P7 TV/ VIDEO)
2. Turn on the external AV equipment.
2. Connect the audio cables to the DVD player’s AUDIO L and Rports and to the L and R AUDIO INPUT ports
on the TV.
How to use
1. Select COMPONENT, (see P7 TV/ VIDEO)
2. Turn on the DVD set.
How to connect component video:
1. Connect the three separate component video cables to the DTV set-top box Y, Pb and Pr ports and to the
Y, Pb and Pr ports on the TV.
2. Connect the audio cables to the DTV set-top box AUDIO L and Rports and to the Land R AUDIO AV ports
on the TV.
1. Composite Video:
Connect your camera,
camcorder, videogame
set… to Audio port
(Audio L for mono) and
Video port .
Connect DTV set top
box RF output to TV
Antenna input (TV
channel set to CH3 or
CH4). If your DTV set
top box has component
(Y, Pb, Pr) video ports,
use them for better
picture.

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How to use
1. Select COMPONENT
2. Turn on the DTV set-top box set.
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.
1. The earphone jack is located at the rear corner of the TV.
2. The
MUTE key on the remote control works on both internal speaker and the earphone.
3. Use volume key to adjust the volume.
Note: When a TV channel or external AV source is blocked because of a rating set via the Parental control menu,
also the headphone is muted.
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 cord 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.

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REGULATORY NOTICES
Federal Communications Commission Notice
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15
of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a
residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instructions, may cause harmful interference to radio communications. However,
there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful
interference to radio or television reception, which can be determined by turning the equipment off and on, the user
is encouraged to try to correct the interference by one or more of the following measures:
˙Reorient or relocate the receiving antenna.
˙Increase the separation between the equipment and the TV.
˙Connect the equipment into wall power outlet on a circuit different from that to which the receiver is connected.
˙Consult the dealer or an experienced radio or television technician for help.
Modifications –
The FCC requires the user to be notified that any changes or modifications made to this device that are not
expressly approved by Norcent Technology Inc. may void the user’s authority to operate the equipment.
Cables –
Connections to this device must be made with shielded cables with metallic RF/EMI connector hoods to maintain
compliance with FCC Rules and Regulations.
Canadian notice –
This Class B digital apparatus meets all requirements of the Canadian Interference-Causing Equipment
Regulations.
Avis Canadian –
Cat apparel numerous de la classed B respected toutes les exigencies du règlement sur le materiel
brouilleur du Canada.

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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
1
6
11 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
3.2 Factory Preset Display Modes
Analog RGB input signal timing
VESA MODES
Horizontal Vertical
Mode Resolution Total
Nominal
Frequency
+/- 0.5kHz
Sync
Polarity
Nominal
Freq.
+/- 1 Hz
Sync
Polarity
Nominal
Pixel
Clock
(MHz)
VGA 640x480@60Hz 800 x 525 31.469 N 59.940 N 25.175
800x600@56Hz 1024 x 625 35.156 N/P 56.250 N/P 36.000
SVGA
800x600@60Hz 1056 x 628 37.879 P 60.317 P 40.000
XGA 1024x768@60Hz 1344x806 48.363 N 60.004 N 65.000
1280x768@60Hz 1664x798 47.396 P 59.995 N 68.250
WXGA 1360x768@60Hz 1792x795 47.712 P 60.015 P 85.500

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4. Mechanical Instructions
Step Figure Description
Preparation
and
remove
the base
Remove the
screws
remarked in red
Remove
back cover
Remove the
screws
remarked in red

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Remove
shield
Remove the
screws
remarked in red
Remove
the boards
Remove
connectors and
the screws
remarked in red

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Remove
main frame
Remove screws
remarked in red
The end N/A