AOC LM520i User manual

SERVICE MANUAL
LM520iMonitor
(With CPTXG08 PANEL)
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 OFTHIS INFORMATION AFTER THE DATE OF
PUBLICATION AND DISCLAIMS RELIABILITY FOR CHANGES, ERRORS OR OMISSIONS.
MANUFACTURE DATA ：Feb-22-04

2
TABLE OF CONTENTS
PAGE
1. SPECIFICATIONS .................................................................................................... 3
1-1 GENERAL SPECIFICATIONS ...................................................….............. 3
1-2 LCD MONITOR DESCRIPTION .................................................................. 4
1-3 INTERFACE CONNECTOR .................................................................……. 4
2. PRECAUTION AND NOTICES ................................................................................ 5
2-1 ASSEMBLY PRECAUTION ......................................................................... 5
2-2 OPERATIONG PRECAUTION ..................................................................... 5
2-3 STORAGE PRECAUTION …........................................................................ 5
2-4 HIGH VOLTAGE WARNING ....................................................................... 5
3. OPERATING INSTRUCTIONS ................................................................................ 6
4. ADJUSTMENT .......................................................................................................... 7
4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS ............................... 7
4-2 ADJUSTMENTS METHOD .& DESCRIPTION........................................... 7
4-3 FRONT PANEL CONTROL KNOBS ............................................................ 8
5. CIRCUIT & SOFTWARE DESCRIPTION ................ 9
5-1 THE DIFFERENT BETWEEN EACH PANEL ……………………………. 9
5-2 SPECIAL FUNCTION WITH PRESS KEY ……………………………….. 10
5-3 SIMPLE INTRODUCTION ABOUT LM500 CHIPSET …………………... 11
5-4 SOFTWARE FLOW-CHART 13
6. TROUBLE SHOOTING............................................................................................. 15
A).MAIN BOARD TROUBLE SHOOTING CHART .. .................................... 15
B). INVERTER - MODULE TROUBLE SHOOTING CHART ........................... 19
7. MECHANICAL OF CABINET FRONT DIS-ASSEMBLY...................................... 21
8. PARTS LISTING .........................................................................................………... 22
9. SCHEMATIC.............…………………………………............................................ 34
10. PCB LAYOUT .....................................................................………………………... 37

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1. SPECIFICATIONS FOR LCD MONITOR
1-1 General specifications
1. LCD-PANEL :
Active display area 15 inches or 15.1 inches diagonal
Pixel pitch 0.297 mm x0.297 mm
Pixel format 1024 x768 RGB vertical stripe arrangement
2. Display Color :
6-bit, 262144 colors or 8-bit, 16.7 million colors
3. ●External Controls :
a).Power On/Off, Auto key, Rotary-knob ( for shuttle)
b).Power On/Off, Auto key, Left key, Right key ( for 4-key )
●OSD menu Controls
Contrast, Brightness, Focus, Clock,H-position, V-position, Language, Recall-C2(warm color), Recall-C1 (Cool
color), Reset, Exit-OSD, Red, Green, Blue
4. Input Video Signal :
Analog-signal 0.7Vpp
Video signal termination impedance 75 OHM
5. Scanning Frequencies :
Horizontal: 29 KHz - 63 KHz
Vertical: 55 Hz – 75 Hz
Pixel clock: 80 MHz
6. Factory Preset Timing : 18
User Timings : 19
Input signal tolerance : H tolerance ±1 K, V tolerance ±1 Hz
7. Power Source :
Switching Mode Power Supply
AC 100 – 240 V, 50/60 Hz Universal Type
8. Operating Temperature : 5℃- 35℃Ambient
Non-operating Temperature : -20℃- 60℃
9. Humidity :
Operating : 20% to 80% RH (non-condensing)
Non Operating : 5% to 95%RH (38.7℃maximum wet bulb temperature)
10. Weight : 3.0 kg
11. External Connection : 15Pin D-type Connector, AC power-Cord
12. View Angle : x-axis right/left = 60, y-axis up/down = 45 ,45
13. Outside dimension : Width x Height xThickness = 356mm x358mm x160mm
14. Plug and Play : VESA DDC1/DDC2B
15. Power saving : VESA DPMS

4
1-2 LCD MONITOR DESCRIPTION
The LCD MONITOR will contain an main board, an inverter/power board, keypad board and internal
adapter which house the flat panel control logic, brightness control logic and DDC.
The power board will provide AC to DC Inverter voltage to drive the backlight of panel and the main board
chips each voltage.
1-3 Interface Connectors
(A) AC-Power Cable
(B) Video Signal Connectors and Cable
(C) Audio Cable
Power board
(include: adapter, inverter)
Flat Panel and
CCFL backlight
Main Board
Keyboard
RS232 Connector
For white balance
adjustment in factory
mode
HOST Computer
CCFL Drive.
AC-IN
100V-240V Video signal, DDC
Monitor Block Diagram

5
2. PRECAUTIONS AND NOTICES
2-1 ASSEMBLY PRECAUTION
(1) Please do not press or scratch LCD panel surface with anything hard. And do not soil LCD panel surface by
touching with bare hands (Polarizer film, surface of LCD panel is easy to be flawed)
In the LCD panel, the gap between two glass plates is kept perfectly even to maintain display characteristic and
reliability. If this panel is subject to hard pressing, the following occurs :
(a) Uniform color (b) Orientation of liquid crystal becomes disorder
(2) Please wipe out LCD panel surface with absorbent cotton or soft cloth in case of it being soiled.
(3) Please wipe out drops of adhesive like saliva and water in LCD panel surface immediately.
They might damage to cause panel surface variation and color change.
(4) Do not apply any strong mechanical shock to the LCD panel.
2-2 OPERATING PRECAUTIONS
(1) Please be sure to unplug the power cord before remove the back-cover. (be sure the power is turn-off)
(2) Please do not change variable resistance settings in MAIN-BOARD, they are adjusted to the most suitable value. If
they are changed, it might happen LUMINANCE does not satisfy the white balance spec.
(3) Please consider that LCD backlight takes longer time to become stable of radiation characteristic in low
temperature than in room temperature.
(4) Please pay attention to displaying the same pattern for very long-time. Image might stick on LCD.
2-3 STORAGE PRECAUTIONS
(1) When you store LCD for a long time, it is recommended to keep the temperature between 5℃-35℃ without the
exposure of sunlight and to keep the humidity less than 80% RH.
(2) Please do not leave the LCD in the environment of high humidity and high temperature such as 60℃90%RH.
(3) Please do not leave the LCD in the environment of low temperature; below -15℃.
2-4 HIGH VOLTAGE WARNING
The high voltage was only generated by INVERTER module, if carelessly contacted the transformer on this module,
can cause a serious shock. (the lamp voltage after stable around 600V, with lamp current around 8mA, and the lamp
starting voltage was around 1500V, at Ta=25℃)

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3. OPERATING INSTRUCTIONS
This procedure gives you instructions for installing and using the LM520 LCD monitor display.
1. Position the display on the desired operation and plug–in the power cord into External Adapter 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
PIN NO. DESCRIPTION PIN NO. DESCRIPTION
1. RED 9. 5V power from VGA-card
2. GREEN 10. GND
3. BLUE 11. SYNC. GND
4. GND 12. SDA
5. GND 13. HORIZ. SYNC
6. GND-R 14. VERT. SYNC
7. GND-G 15. SCL
8. GND-B
3. Apply power to the display by turning the power switch to the "ON" position and allow about thirty seconds for
Panel warm-up. The Power-On indicator lights 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-key to get the best picture-quality.
5. This monitor has power saving function following the VESA DPMS. Be sure to connect the signal cable to the PC.
6. If your LCD monitor requires service, it must be returned with the power cord & Adapter.
1
6
11 15
5
10

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4. ADJUSTMENT
4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS
Adjustments should be undertaken only on following function : contrast, brightness focus, clock, H-position, V-
position, red, green, blue since C1 color & C2 color.
No volume adjust description
4-2 ADJUSTMENT METHOD
Press MENU button to activate OSD Menu or make a confirmation on desired function, Press Left/Right button to select
the function or done the adjustment.
1. White-Balance, Luminance adjustment
Approximately 30 minutes should be allowed for warm up before proceeding white balance adjustment.
2. Clock adjustment
Set the Chroma at pattern 63 (cross-talk pattern) or WIN98/95 shut-down mode (dot-pattern).
Adjust until the vertical-shadow as wide as possible or no visible.
This function is adjust the PLL divider of ADC to generate an accurate pixel clock
Example : Hsyn = 31.5KHz Pixel freq. = 25.175MHz (from VESA spec)
The Divider number is (N) = (Pixel freq. x 1000)/Hsyn
From this formula, we get the Divider number, if we fill this number in ADC register (divider register), the PLL of
ADC will generate a clock which have same period with above Pixel freq.(25.175MHz) the accuracy of this clock
will effect the size of screen.(this clock was called PIXEL-CLOCK)
3. Focus adjustment
Set the Chroma at pattern 63 (cross talk pattern) or WIN98/95 shut down mode (dot-pattern).
Adjust the horizontal interference as less as possible
This function is adjust the phase shift of PIXEL-CLOCK to acquire the right pixel data .
If the relationship of pixel data and pixel clock not so match, we can see the horizontal interference at screen only
at crosstalk pattern and dot pattern we can find this phenomena, other pattern the affect is very light
4. H/V-Position adjustment
Set the Chroma at pattern 1 (crosshatch pattern) or WIN98/95 full-white pattern confirm above item 2 & 3
functions (clock & focus) was done well, if that 2 functions failed, the H/V position will be failed too. Adjust the
four edge until all four-edges are visible at the edge of screen.
5. MULTI-LANGUAGE function
There have 6language for selection, press “MENU” to selected and confirm , press “ LEFT” or “ RIGHT” to
change the kind of language ( English , Deutch , Francais, Espanol, Italian,Chinese)
6. Reset function
Clear each old status of auto-configuration and re-do auto-configuration ( for all mode)
This function also recall C2 color-temperature , if the monitor status was in “ Factory-mode” this reset function
will clear Power-on counter ( backlight counter) too.
7. View Power-on counter and reset the Power-on counter( if not necessary , not suggest to entry factory mode)
The Power-on counter was used to record how long the backlight of panel already working, the backlight life time
was guarantee minimal 25000 hours, the maintainer can check the record only in factory mode.

8
Press MENU button for 2 seconds along with plug-in AC power cord will be in factory mode, and the OSD screen
will located at left top of panel but take cautions don’t press icon “C2” & “C1”, if you press C2/C1 , your
white-balance data will overlap with the new-one, and you must perform the white-balance process again.
The result of counter was place at top of OSD, the maximal of record memory was 65000 hours, if exceed 65000
hours the counter will keep in 65000 hours until press “ RESET” at osd-menu in factory mode.
The “ RESET” function in factory mode will execute following function:
1. clear the Power-on counter to zero hours
2. clear old auto-configuration status for all mode , so the monitor will automatically re-do auto-config when
change to next mode or power on-off
4-3 FRONT PANEL CONTROL KNOBS
Power button : Press to switch on or switch off the monitor.
Auto button : to perform the automatic adjustment from CLOCK, FOCUS, H/V POSITION, but no affect the color-
temperature, and to exit the OSD
Left/Right button : select function or do an adjustment. Or adjust volume
MENU button : to activate the OSD window or to confirm the desired function

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5. CIRCUIT-DESCRIPTION
5-1 PANEL SPECIFICATION (CPT XG08)
5-1-1Panel Feature
－15” XGA TFT LCD Panel
－2 CCFLS Backlight System
－Supported (H1024Pixel ×V768Lines) resolution
－By applying 6 bit digital data
5-1-2 Display Characteristics
Items Specification Unit
Display Area 304.128(H) x 228.096 (V) mm
Driver element a-Si TFT active matrix
Display color Over 16 million Colors
Number of pixels 1024 x 768 pixel
Pixel Arrangement RGB vertical stripe
Pixel pitch 0.297(H) x 0.297(V) mm
Display Mode Normally White
5-1-3 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 300 400 -
Rising Tr
Response
Time Falling Tf Tf+Tr =35 Msec
Luminance of White
(Center of screen) YL 200 250 - Cd/m2
Rx 0.623
Ry 0.335
Gx 0.293
Gy 0.599
Bx 0.144
By 0.113
Wx 0.310
Color
Chromaticity
(CIE 1931)
Coordinates (CIE)
Wy
Normal
ψ=0
θ=0
Viewing
Angle
Typ.
-0.03
0.330
TYP.
+0.03
Brightness Uniformity [%] 70 75 -
5-1-4 Parameter guide line for CCFL Inverter
INVERTER MAX BRINGTHNESS (Vadj:5.0v), LOAD=120KΩX4
(ROOM TEMPERATURE 25℃±4℃)

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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
5-2 SPECIAL FUNCTION with PRESS-KEY
press Menu button during 2 seconds along with plug-in the AC Power cord:
That operation will set the monitor into “Factory- mode”, in Factory mode we can do the White balance adjustment
with RS232 , and view the Backlight counter (this counter is use to record the panel activate hours ,for convenient
the maintainer to check the panel backlight life time)
In Factory mode, OSD-screen will locate in left top of screen.
Press POWER-button off to on once will quit from factory mode and back to user-mode.
OSD-INDEX EXPLANATION
1. CABLE NOT CONNECTED: Signal-cable not connected.
2. INPUT NOT SUPPORT:
a. INPUT frequency out of range: H > 63kHz,v > 75Hz or H < 28kHz, v < 55Hz

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b. INPUT frequency out of VESA-spec. (out of tolerance too far)
3. UNSUPPORT mode, try different Video-card Setting:
Input frequency out of tolerance, but still can catch-up by our system (if this message show, that means, this is new-
user mode, AUTO-CONFIG will disable)
5-3 SIMPLE-INTRODUCTION about LM520A chipset
MODULE-TPYE COMPONENT : Inverter/Power Board
OSD
Control
Interface
(CN
5
03
)
Scalar
gm5115/gm2115
(Include MCU,ADC,OSD)
(U203)
Flash
Memory
A290011TL-70
(U202)
EEP
ROM
24C16
D-Sub
Connector
(CN1)
EEPROM
24C02
(U104)
RGB
RXD
TXD
DB15_SDA,
DB15_SCL
EPR_SDA
EPR_SCL
LCD
Interface
(
CN501/CN502
))
DVI-I only
Connector
(CN101)
EEPROM(D-I
only)
24C02

12
Inverter Block Diagram

13
5-4 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

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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.
Scaler 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 after 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 ?

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6. Trouble Shooting
6-1.MAIN BOARD
1.NO SCREEN APPEAR
Note:1. if Replace “MAIN-BOARD” , Please re-do “DDC-content” programmed & “WHITE-Balance”.
2. if Replace “Power Board” only, Please re-do “ WHITE-Balance”
Led orange
NG
OK ,Panel Power OK
OK, input Normal
Check U203 Data-output Block
Replace Power board and Check
Inverter control relative circuit
Re-do White balance adjust
Measured Crystal X201(14.318MHz)
OK, clock
normal
Replace U203 (GM5115/2115)
OK
Check CN504 pin 10 = 2.5 V?
Check CN504 pin 8 = 3.3 V?
Check CN504 pin 4 = 5 V?
Measured CN402 pin 1/2 = 5V?
Measured CN402 pin 3/4
=
Check Correspondent component.
Is there any shortage or cold solder?
Check Power Board.
Yes .there have OSD showYes, all DC level exist
Disconnected the Signal cable( Loose the
Signal cable ),Is the screen show “Cable Not
Connected” ?
Connected the Signal cable again,
Check LED status.
Led Green
Replace U202
Flash Rom
No, nothing is show
Connected the Signal cable
again, Check LED status.
Check Power switch is in Power-on
status and check if Power switch had
been stuck ?
Led Orange
OK, Keyboard no stuck
Led Green
Check the Wire-Harness from CN501 or CN502
was tight enough?,
check the Wire connection to panel side too
Measured RGB (R136,R138,R140)
H,V Input at U106 pin 4,2 ,was there
have signal ?
Check digital signal from CN1
Check Correspondent
component
short/open
( Protection Diode )
and Signal cable
bad ?
OK,Wire tight enough
Check Panel-Power Circuit Block
OK, U203 data OK

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PANEL-POWER CIRCUIT
INVERTER Control Relative Circuit
SCILLATOR BLOCK
U200-DATA OUTPUT
OK,R225 have
check R824 should have response from 14V
t
0V
When
we
switch
the
power
switch
from
on
t
Check the PPWR panel power relative circuit,
R223、Q200、Q201(pin2)
In normal operation, when LED =green, R223
should =0 v,
If PPWR no-response when the power switch
Turn
on
and
turn
off,
replace
the
U501
-
GMZAN1
NG
Measured the Q201 pin 2= 3.3 V? Replace Q201 ( Nmos)
NG, no Voltage
OK,
Replace INVERTER-module
& Re-do white balance
Replace INVERTER to new-one, and
Check the screen is normal ??
Measured the inveter connector CN30
3
Pin 1=14V, pin 3 on/off control=5V
(on)
NG, still no screen
Check the Bklt-On relative circuit, R315, Q304,
R311,
In normal operation, when LED =green,
R315 Bklt-On should =0 v,
If Bklt-On no-res
p
onse when the
p
ower switch tur
n
NG
NG
OK
OK
Measured U201 Oscillator output R215= 50mhZ ? Replace Oscillator U201
NG , no
transition
OK, has
transitio
Measured X300 Crystal output = 20mhZ ? Replace Crystal X300
NG ,no
transition
OK
Check Q201 pin 3= 3.3V
Yes
Measured PCLK(L207)
PVS,PHS (pin 73,74 from U200 )
Is there have any transition?
Pclk around 28MHz to 40 MHZ , PVS=60.09Hz ,
PHS around 50KHz-52 KHz ??(refer to input
signal
=
640x480@60
Hz
31k,
and
LED
is
green)
Replace GMZAN1 (U200) or replace
MAINBOARD.
NG , no
transition
If Main Board being replace , please
do the EDID programming
OK

17
2.PANEL POWER CIRCUIT
3.INVERTER Control Relative Circuit
check R507 should have response
from 0V to 3.3V
When we switch the power switch fro
m
on to off
NG Check the PPWR panel power relative circuit, Q501, Q502
In normal operation, when LED =green, R507 should =0 v,
If PPWR no-response when the power switch
Turn on and turn off, replace the U203-GM5120/2120
OK NG, no Voltage
Measured the Q501 pin 3= 3.3 V? Check U202 pin 2= 3.3V
OK
OK,
Replace Q501 ( AO3401)
Yes
NG Check the Bklt-On relative circuit, R357, R358,
In normal operation, when LED =green,
R357 Bklt-On should =5 v,
If Bklt-On no-response when the power switch
turn on-off, Replace U203 GM5115/2115
NG, still no screen
OK
NG Replace Power board
& Re-do white balance
Measured the inverter connector
CN504
pin1 on/off control=3.3V (on)
pin2 PWM signal control dim 0V-5V
Replace power board to new-one
and check the screen is normal?

18
4.U203-DATA OUTPUT
Measured DCLK DVS, DHS (pin 117,116
from U203 ) Is the waveform ok?
DCLK around 40 MHz , DVS=60.09Hz , DHS
around 80 KHz ?(refer to input signal=
640x480@60 Hz 31k, and LED is Green)
NG , no transition
OK
Replace GM5115 /2115
(U203) or replace Main
board.
Check U203 GM5115 /2115
Signal output ER0~7,EG0~7,EB0~7
OR0~7,OG0~7,OB0~7
Is the waveform ok ?
Check CP501—CP511 or LP501—
LP509 or RP201 or RP202 or Q501
or Q502
Signal output Is the waveform ok ?
OK
If Main Board being replace ,
please do the DDC – content
reprogrammed
Replace CP501—CP511 or
LP501—LP509 or RP201 or
RP202 or Q501 or Q502
replace MAINBOARD.
OK

19
6-2.Power/Inverter Board
1.) No power

20
2.) W / LED , No Backlight