AOC LM721A User manual

LM721A Service Manual Rev: A
Page 1 of 56
17” LCD Monitor
LM721A
THESE DOCUMENTS ARE FOR REPAIR SERVICE INFORMATION ONLY. EVERY REASONABLE
EFFORT HAS BEEN MADE TO ENSURE THE ACCURACY OF THIS MANUAL; WE CANNOT GUARANTEE
THE ACCURACY OF THIS INFORMATION AFTER THE DATE OF PUBLICATION AND DISCLAIMS RE
LIABILITY FOR CHANGES, ERRORS OR OMISSIONS.
Prepared: LiuYongFeng
Date: May-16-04
SERVICE MANUAL

LM721A Service Manual Rev: A
Page 2 of 56
Revision History
Revision Date Page Items Modification
A May-16-04 All First version release;

LM721A Service Manual Rev: A
Page 3 of 56
TABLE OF CONTENTS
TABLE OF CONTENTS---------------------------------------------------------------------------------------------------3
1.MONITOR SPECIFICATIONS---------------------------------------------------------------------------------5
2. LCD MONITOR DESCRIPTION -------------------------------------------------------------------------------6
3. OPERATING INSTRUCTIONS -------------------------------------------------------------------------------7
3.1 GENERAL INSTRUCTIONS ---------------------------------------------------------------------------------------7
3. CONTROL BUTTONS -------------------------------------------------------------------------------------------7
3.3 ADJUSTING THE PICTURE-------------------------------------------------------------------------------------7
4. INPUT/OUTPUT SPECIFICATION-----------------------------------------------------------------------------9
4.1 INPUT SIGNAL CONNECTOR ------------------------------------------------------------------------------9
4.2 FACTORY PRESET DISPLAY MODES -------------------------------------------------------------------- 10
4. POWER SUPPLY REQUIREMENTS ------------------------------------------------------------------------ 11
4.4 PANEL SPECIFICATION (QDI EL07) --------------------------------------------------------------------12
5. BLOCK DIAGRAM ---------------------------------------------------------------------------------------------------14
5.1 MONITOR EXPLODED VIEW --------------------------------------------------------------------------14
5.2 SOFTWARE FLOW CHART-------------------------------------------------------------------------------15
5.3 ELECTRICAL BLOCK DIAGRAM -----------------------------------------------------------------------17
6. SCHEMATIC -------------------------------------------------------------------------------------------------------20
6.1 MAIN BOARD------------------------------------------------------------------------------------------------------20
6.2 INVERTER/POWER BOARD-----------------------------------------------------------------------------23
6.3 KEY BOARD -----------------------------------------------------------------------------------------------26
7. PCB LAYOUT -------------------------------------------------------------------------------------------------27
7.1 MAIN BOARD--------------------------------------------------------------------------------------------------------27
7.2 INVERTER/POWER BOARD------------------------------------------------------------------------------------29

LM721A Service Manual Rev: A
Page 4 of 56
7.3 KEYPAD BOARD AND AUDIO BOARD---------------------------------------------------------------------31
8. MAINTAINABILITY --------------------------------------------------------------------------------------------------32
8.1 EQUIPMENTS AND TOOLS REQUIREMENTS ----------------------------------------------------32
8.2 TROUBLE SHOOTING -----------------------------------------------------------------------------------33
9. WHITE-BALANCE, LUMINANCE ADJUSTMENT -------------------------------------------------39
10. BOM LIST --------------------------------------------------------------------------------------------------------40

LM721A Service Manual Rev: A
Page 5 of 56
1. Monitor Specifications
Driving system TFT Color LCD
LCD Panel Size 43.2cm(17.0")
Pixel pitch 0.264mm( H )x 0.264mm( V )
Viewable angle 150˚(H) 110˚(V)
Response time (typ.) 16 ms
Video Analog /Digital
Input Sync. Type H/V TTL
H-Frequency 30kHz – 80kHz
V-Frequency 55-75Hz
Display Colors Over 16 million Colors
Dot Clock 135MHz
Max. Resolution 1280 x 1024
Plug & Play VESA DDC2BTM
Power Consumption ON Mode <45W
OFF Mode
<3W
Maximum Screen
Size
Horizontal : 13.3”(337.92mm)
Vertical : 10.6”(270.336mm)
Power Source 100~240VAC,47~63Hz
Environmental
Considerations
Operating Temp: 0°C to 40°C
Storage Temp.: -20°C to 60°C
Operating Humidity : 15% to 90%
Weight (N. W.) Packaged 7.0Kg Unit
Unpackaged 5.0Kg Unit

LM721A Service Manual Rev: A
Page 6 of 56
2. Lcd Monitor Description
The LCD MONITOR will contain a main board, an inverter/power board, keypad board , Audio board
and external power adapter which house the flat panel control logic, brightness control logic and
DDC.
The Inverter board will drive the backlight of panel and the DC-DC conversion.
The Adapter will provide the 12V DC-power to inverter/power board.
Inverter/Power board
Flat Panel and
CCFL backlight
Main Board
Keyboard
RS232 Connector
For white balance
adjustment in
factory mode
HOST Computer
CCFT Drive.
DC-IN 12V
Video signal, DDC
Monitor Block Diagram

LM721A Service Manual Rev: A
Page 7 of 56
3. Operating Instructions
3.1 General Instructions
Press the power button to turn the monitor on or off. The other control buttons are located at front panel of the monitor. By
changing these settings, the picture can be adjusted to your personal preferences.
-The power cord should be connected.
-Connect the video cable from the monitor to the video card.
-Press the power button to turn on the monitor, the power indicator will light up.
3.2. Control Buttons
-Power Button:
When pressed, the monitor enters the off mode, and the LED turns blank. Press again to restore normal status.
-Left / Right Button:
When the OSD show on screen, Left/Right Button are used to control the monitor functions. Press to switch functions or adjust
settings. And if the OSD off, Left/Right buttons are used to control the audio volume;
-Auto Adjust Key:
The Auto Adjust Key is used to automatically set the H Position, V Position, Clock and Phase.
-Power Indicator:
Green — Power On mode.
Orange — Power Saving mode.
Blank —Power Off Mode.
A B C D E F
Menu Volume Auto LED Power
A. Menu button
B. Left button/Volume down
C. Right button/Volume up
D. Auto button/Exit
E. Indicator light
F. Power button
3.3 Adjusting the Picture
CONTROL Buttons

LM721A Service Manual Rev: A
Page 8 of 56
OSD Table:
1.
Contrast Adjust the picture contrast.
2. Brightness Adjust the picture brightness.
3. Focus Adjust picture Focus.
4. Clock Adjust picture Clock.
5.
H_Position Adjust the horizontal position of the picture.
6. V.Position Adjust the vertical position of the picture.
7. Input Selected
Input Signal source sleeted (select Analog or Digital input
source).
8. Language Multi-Language selection
9. Dos-mode selected
Dos-mode resolution selection for 720x400 @70Hz and
640x400 @70Hz
10. Red Adjusts Red intensity.
11. Green Adjusts Green intensity.
12. Blue Adjusts Blue intensity.
13. C1 (Warm) Color Set the color temperature to warm white.
14. C2 (Cool) Color Set the color temperature to cool white.
15.
Reset
Clear each old status of Auto-configuration and re-do
auto-configuration .
16. Exit Save user adjustment and OSD disappear.

LM721A Service Manual Rev: A
Page 9 of 56
4. Input/Output Specification
4.1 Input Signal Connector
PIN NO. DESCRIPTION
PI N NO.
DESCRIPTION
1. Red 9. +5V
2. Green 10. Detect Cable
3. Blue 11. NC
4. Ground 12. DDC-Serial Data
5. Ground 13. H-Sync
6. R-Ground 14. V-Sync
7. G-Ground 15. DDC-Serial Clock
8. B-Ground
VGA connector layout
15
610
11 15

LM721A Service Manual Rev: A
Page 10 of 56
4.2 Factory Preset Display Modes
VESA MODES
Horizontal Vertical
Mode Resolution Total
Nominal
Frequency
+/- 0.5kHz
Sync
Polarity
Nominal
Freq.
+/- 1 Hz
Sync
Polarity
Nominal Pixel
Clock
(MHz)
640x480@60Hz 800 x 525 31.469 N 59.940 N 25.175
640x480@72Hz 832 x 520 37.861 N 72.809 N 31.500
VGA
640x480@75Hz 840 x 500 37.500 N 75.00 N 31.500
800x600@56Hz 1024 x 625 35.156 N/P 56.250 N/P 36.000
800x600@60Hz 1056 x 628 37.879 P 60.317 P 40.000
800x600@72Hz 1040 x 666 48.077 P 72.188 P 50.000
SVGA
800x600@75Hz 1056x625 46.875 P 75.000 P 49.500
1024x768@60Hz 1344x806 48.363 N 60.004 N 65.000
1024x768@60Hz 1312x813 48.78 N 60.00 N 64.000
1024x768@70Hz 1328x806 56.476 N 70.069 N 75.000
1024x768@72Hz 1304x798 57.515 P 72.074 P 75.000
1024x768@75Hz 1328x804 60.200 N 74.90 N 80.000
XGA
1024x768@75Hz 1312x800 60.023 P 75.029 P 78.750
XGA 1152x864@75Hz 1600x900 67.50 P 75.000 P 108.000
1280x1024@60Hz 1688x1066 63.981 P 60.020 P 108.000
SXGA 1280x1024@75Hz 1688x1066 79.976 P 75.025 P 135.000
IBM MODES
Horizontal Vertical
Mode Resolution Total
Nominal
Frequency
+/- 0.5kHz
Sync
Polarity
Nominal
Freq.
+/- 1 Hz
Sync
Polarity
Nominal
Pixel
Clock
(MHz)
DOS* 720x400@70Hz 900 x 449 31.469 N 70.087 P 28.322
DOS** 640x400@70Hz 800 x 449 31.469 N 70.087 P 25.175
MAC MODES
VGA 640x480@67Hz 864x525 35.000 N 66.667 N 30.240
SVGA 832x624@75Hz 1152x667 49.725 N 74.551 N 57.2832

LM721A Service Manual Rev: A
Page 11 of 56
4.3 Power Supply Requirements
4.3.1 Input Requirements
PARAMETER RANGE CONDITION
Input AC Voltage 100 to 240VAC RMS Universal input full range
Input Frequency 60Hz @ 100VAC to 50Hz @
240VAC
Input Current Less than 2.0 Amps RMS Input voltage 100 VAC RMS ; 60 Hertz.
Parameter must be reached within 3 seconds of
turn-on.
Less than 1.0 Amps RMS Input voltage 220 VAC RMS ; 50 Hertz.
Parameter must be reached within 3 seconds of
turn-on.
Input Power Less than 75 Watts
Power factor >
0.5
Input voltage 120 VAC RMS ; 60
Hertz
Inrush Current Less than 30 A peak Input voltage 100 VAC RMS ; 60 Hertz at all
Phase(0, 90, 180, 270 degree)
Less than 50 A peak Input voltage 240 VAC RMS ; 50 Hertz at all
Phase(0, 90, 180, 270 degree)
Input Fusing Fuse should be located internal to
the adapter, easily accessible
when the cover is removed
Fuse must be UL/CSA approved. Fuse value
must no have to change for 115 VAC or 230 VAC
operation
Leakage Current Less than 3.5 mA Input voltage 240 Volts RMS ; 50 Hertz
Hi-Pot Primary to secondary 1.5KVAC for 1 Minute(leakage current 10mA)
1.8KVAC for 1 Minute(leakage current 10mA)
3.0KVAC for 1 Minute(leakage current 10mA)
without Y-cap & Coupling cap.
Prima1ry to Safety Ground 1.5KVAC for 1 Minute(leakage current 10mA)
1.8KVAC for 1 Minute(leakage current 10mA)
4.3.2 Output Requirements
PARAMETER RANGE CONDITION
DC Out 12VDC ± 5% Min 0A Max 3.75A
Load Regulation 12.0V(12.12V) ± 5% 11.4 to 12.6VDC
Dynamic Load
Regulation
A
ny frequency up to 250Hz(duty
50%)
±5% for 10% to 100%, 100% to 10% load
change for
+12Vdc
Ripple & noise 170mVpp at 12VDC Input voltage : 100VAC at 60Hz 240VAC at
50Hz
* Ripple and noise are measured.
Output current
protection
less than 7.0A, more than 12.0
A
at 12.0VDC
Current exceeds maximum rateing more than
20%
Leakage Current Less than 0.25 mA Input voltage 100 Volts RMS ; 50 Hertz
Less than 0.5 mA Input voltage 240 Volts RMS ; 50 Hertz

LM721A Service Manual Rev: A
Page 12 of 56
4.4 PANEL SPECIFICATION (Hydis-200)
4.4.1 Panel Feature
-High contrast ratio, high aperture structure
-TN(Twisted Nematic) mode
-Wide viewing angle
-High speed response
-SXGA(1280 x 1024 pixels) resolution
-Low power consumption
-2 dual CCFTs(Cold Cathode Fluorescent Tube)
-DE(Data Enable) mode
-COMPACT SIZE DESIGN
4.4.2 Display Characteristics
Items Specification Unit
Display Area 337.92(H) x 270.336(V) mm
Driver element a-Si TFT active matrix
Display color 16.2M Colors
Number of pixels 1280 x 1024 pixel
Pixel Arrangement RGB vertical stripe
Pixel pitch 0.264(H) x 0.264(W) mm
Display Mode Normally White
4.4.3 Optical Characteristics
The optical characteristics are measured under stable conditions at 25 (Room Temperature)℃:
Item Symbol Conditions Min. Typ. Max. Unit Note
Contrast Ratio
(Center of screen) C/R 250 450 -
Rising Tr - 4 5
Response
Time Falling Tf - 12 20
msec
Luminance of White
(Center of screen) YL 200 260 - Cd/m2
Rx 0.64
Ry 0.34
Gx 0.29
Gy 0.61
Bx 0.14
By 0.07
Wx 0.3
Color
Chromaticity
(CIE 1931)
Coordinates (CIE)
Wy
Normal
ψ=0
θ=0
Viewing
Angle Typ.
-0.03
0.338
TYP.
+0.03
Brightness Uniformity [%] 75 80 -

LM721A Service Manual Rev: A
Page 13 of 56
4.4.4 Parameter guide line for CCFL Inverter
INVERTER MAX BRINGTHNESS (Vadj:5.0v), LOAD=120KΩX4(ROOM TEMPERATURE 25 ±4℃℃)
ITEM SYMBOL MIN. TYP. MAX. UNIT REMARK
Input voltage Vin 10.8 12 13.2 V
Input current Iin 2250 2500 mA FOR 4 LOAD
Output Current Iout 6.0 6.5 7.0 mA FOR 1 LOAD
Frequency F 50.0
55.0 60.0 KHZ
FOR 1 LOAD
H.V open Vopen 1450 1600 1750 Vrms NO LOAD
H.V Load Vload 710 810 910 Vrms RL=120KΩ
Start voltage Vst 1650 1750 1850 Vrms RL=CCFL
Protect delay time PDT 0.4 1 4 Sec
INVERTER MIN BRINGTHNESS (Vadj:0.0v), LOAD=120KΩX4(ROOM TEMPERATURE 25 ±4℃℃)
ITEM SYMBOL MIN. TYP. MAX. UNIT REMARK
input voltage Vin 10.8 12 13.2 V
input current Iin 660 750 mA FOR 4 LOAD
Output Current Iout 3.0 3.5 4.0 mA FOR 1 LOAD
Frequency F
50.0 55.0 60.0 KHZ
FOR 1 LOAD
H.V open Vopen 1450 1600 1750 Vrms NO LOAD
Start voltage Vst 1650 1750 1850 Vrms RL=CCFL
H.V Load Vload 350 450 550 Vrms RL=120KΩ

LM721A Service Manual Rev: A
Page 14 of 56
5. Block Diagram
5.1 Monitor Exploded View

LM721A Service Manual Rev: A
Page 15 of 56
5.2 Software Flow Chart
1
2
N
Y
5
Y
N
10
Y
N
12
Y
N
7
Y
N
6
4
3
8
9
14
11
13
Y
N
1
5
Y
N
16
1
7
19
Y
N
18

LM721A Service Manual Rev: A
Page 16 of 56
Remark:
1) MCU initialize.
2) Is the EEprom blank ?
3) Program the EEprom by default values.
4) Get the PWM value of brightness from EEprom.
5) Is the power key pressed ?
6) Clear all global flags.
7) Are the AUTO and SELECT keys pressed ?
8) Enter factory mode.
9) Save the power key status into EEprom.
Turn on the LED and set it to green color.
Scalar initialize.
10) In standby mode ?
11) Update the life time of back light.
12) Check the analog port, are there any signals coming ?
13) Does the scalar send out a interrupt request ?
14) Wake up the scalar.
15) Are there any signals coming from analog port ?
16) Display "No connection Check Signal Cable" message. And go into standby mode afte
r
the message disappear.
17) Program the scalar to be able to show the coming mode.
18) Process the OSD display.
19) Read the keyboard. Is the power key pressed ?

LM721A Service Manual Rev: A
Page 17 of 56
5.3 Electrical Block Diagram
5.3.1 Main Board
OSD
Control
Interface
(CN403)
Scalar gm5120/gm2120
(Include MCU,ADC,OSD)
(U203)
Flash Memory
W39f010P-70B
(U202)
EEPROM
24C16
(U204)
D-Sub
Connector
(CN102)
EEPROM
24C02
(U104)
Hsync,
Vsync
RGB
RXD
TXD
DB15_SDA,
DB15_SCL
EPR_SDA
EPR_SCL
LVDS
THC63LVDM83R
(U301/U302)
LCD
Interface
(CN301)
DVI-I only
Connector
(CN101)
EEPROM (D-I only)
24C02
(U102)

LM721A Service Manual Rev: A
Page 18 of 56
5.3.2 Inverter/Power Board
Buck Connector Parallet-resonant
Driver Dimming control
(阀菠瓜)
Parallet-resonant
inverter
CCFL
PWM
Dimming control
Driver
Circuit
Vin
Vin inverter
(PW M )
Circuit
Inverter Block Diagram

LM721A Service Manual Rev: A
Page 19 of 56
Power Block Diagram

LM721A Service Manual Rev: A
Page 20 of 56
6. Schematic
6.1 Main Board
VGA_PLUG
U106F
74LVC14
13 12
147
DVI_5V
R101 NC
GND
R163 15 1/16W
R128
NC
CN101
NC (DVI_Connector)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
17
18
19
20
21
23
24
C1
16
22
C2
C3
C4
C5
25
26 T2-
T2+
SGND
T4-
T4+
DDCCLK
DDCDAT
A_VSYNC
T1-
T1+
SGND
T3-
T3+
+5V
GND
T0-
T0+
SGND
T5-
T5+
TC+
TC-
A_RED
HPD
SGND
A_GREEN
A_BLUE
A_HSYNC
A_GND
A_GND
A_GND
R136 120 1/16W
D105
BAV99
6/24
gm5120 E
ANALOG&DIGITAL INPUT
MOZO
C
26Friday, December 06, 2002
Title
Size Document Number Rev
Date: Sheet of
ZD105
MLL5232B 5.6V
R119
NC
C113
0.1uF/16V
USE DVI TX3,4,5 +/- PIN
R160 1M 1/16W
12
NC(1N4148)
D108
R137 47 1/16W
GND
ED108
1 2
C122
NC
GREEN-GPIO4/UART_DI
AGND
R150
0 1/16W
GND
VS_DVI
D104
BAV99
VGA_5V
GREEN+
Connect two grounds at one single point only.
DVI_5V
SCL_IN
ZD103
NC (5.6V)
1 2
R148 100 1/16W
C101
NC
AGND
DVI_5V
GND
FB105
0
R144
4.7K 1/16W
10/16 modify
+A3.3V
C123
NC
U106E
74LVC14
11 10
147
DDC_SCL_A1
ED102
1 2
C108 0.01uF
R120
NC
GND
C109
0.1uF/16V
R140 120 1/16W
GND
C126
0.1uF/16V
DDC_SCL
R121
NC
7-21
DDC_SDA_D
R126
47 1/16W
R130 47 1/16W
R111 NC
AGND
R154
NC
75-ohm terminating resistor
very close to the VGA
conn.
AGND
DDC_SCL_A P.3
R139 47 1/16W
DDC_SDA
ADD1
ZD109
MLL5232B 5.6V
SDA_IN
R149
NC
GND
HOT_PLUG
(8 mil)
GND
R165 15 1/16W
R164 15 1/16W
ED107
1 2
C105 1uF/16V
U106B
3 4
147
FB101
80 OHM
RXC-IN
R147 100 1/16W
GND
VGA_CONN
DDC_5V
DDC_5V
R125 47 1/16W
5/10 change A+3.3V
VGA_5V
HS
VGA_PG
FB103
80 OHM
(10 mil, ┰キ︽ 絬 )
U104
M24C02WMN6
4
81
2
3
7
6
5
GND
VCCA0
A1
A2
WP
SCL
SDA
R155
0 1/16W
DDC_SDA_A P.3
R145 100 1/16W
+A5V
VS
R117
NC
AGND
GPIO5/UART_DO
FB106
0
C111
NC
R122
0 1/16W
Connect two grounds at one single point only.
GND
C106 0.01uF
R138 120 1/16W
RX1-IN
R109
NC
ADD2
ZD108
MLL5232B 5.6V
GND
DDC_SDA_A1
RX2+IN
D103
BAV99
DIGITAL USE
BLUE-
R166
2.2K
AGND
ED103
1 2
AGND
R158
NC
ED106
1 2
+3.3V
D-SUB
AGND
R107
NC
GND
ADC_AGND
VS_DVI
DDCA_5V
+A3.3V
+A5V
R127
NC
R102 筿 叫綼 ANALOG PORT
10/16 modify
GND
AGND
+3.3V
C125
0.1uF/16V
CN102
VGA
1
6
2
7
3
8
4
9
5
11
12
13
14
15
10
S1S2
D101
BAT54C-GS08
C124
NC
FB102
80 OHM
R135
75 1/16W
ZD101
MLL5232B 5.6V
R143 NC
R141 47 1/16W
ED101
1 2
Pins 6/7/8 are R/G/B
return lines resp.
DDC_SDA_A1
ZD106
MLL5232B 5.6V
C110
NC
GND
VGA_5V
R110
NC
ADD D106 4/26
GPIO5/UART_DO
DDC_SCL_D
ZD104
MLL5232B 5.6V
R161 1M 1/16W
RX2- P.3
Bin
DDC_SCL_A1
C107 1uF/16V
C104 0.01uF
GND
R131
2.2K
GND
UART_DO P.3
R102
NC
DGND
C103 1uF/16V
ZD102
NC (5.6V)
1 2
R133
75 1/16W
3
R112 NC
RX0-IN
GND
SCL_IN
RX1+IN
SCL_IN
C102
0.1uF/16V
10/16 modify
ZD107
MLL5232B 5.6V
R132
2.2K
DGND
RED+
RX1+ P.3
RXC- P.3
FB104
0
R116
NC
2
RX2+ P.3
R134
75 1/16W
SDA_IN
UART_DI P.3
SDA_IN
RXC+IN
RED-
DDC_SDA_D
ADD0
DGND
R159
NC
R142
10K 1/16W
ADC_AGND
BLUE+
+A5V
1
SDA_IN
HS_in
ED104
1 2
RX0+ P.3
RX0- P.3
Rin
ED105
1 2
DEL U101&R118 CIRCUIT 4/24
GND
+A5V
RX1- P.3
RX0+IN
D106
BAT54C-GS08
R129 47 1/16W
R123
15K 1/16W
U102
NC (M24CO2)
4
81
2
3
7
6
5
GND
VCCA0
A1
A2
WP
SCL
SDA
R146 100 1/16W
GND
R156
0 1/16W
DDC_SCL_D&DDC_SDA_D CHANGE 4/25
GPIO4/UART_DI
R108
NC
DVI_PLUG P.3
DDC_SCL_D
Gin
R157
NC
GND
RXC+ P.3
AGND
GND
SCL_IN
U106A
1 2
147
R124
15K 1/16W
RX2-IN
R162 1M 1/16W