LG 786LS Schematic

SERVICE MANUAL

17" LCD Monitor

786LS

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 D ISCLAIMS RE LIABILITY FO R CHANGES, ERRORS OR OMISSIONS,

MANUFACTURE DATA : Aug 28 2002 REVISE: Mar 17 2003

TABLE OF CONTENTS

PAGE

1. SPECIFICATIONS .................................................................................................... 3

1-1 GENERAL SPECIFICATIONS ...................................................….............. 3

1-2 LCD MONITOR DESCRIPTION .................................................................. 3

1-3 INTERFACE CONNECTOR .................................................................……. 3

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.....................…………….. 7-8

4-3 FRONT PANEL CONTROL KNOBS ............................................................ 9

5. CIRCUIT & SOFTWARE DESCRIPTION .............,…………………………….... 10

5-1 SPECIAL FUNCTION WITH PRESS KEY ………………………………. 10 5-2 CIRCUIT FUNCTION DESCRIPTION………………………….……….. 10-11 5-3 SOFTWARE FLOW CHART……………………………………………… 12

6. A). INTERFACE-BOARD TROUBLE-SHOOTING CHART .......…………..... 14-21

B). INVERTER –MODULE SPEC &TROUBLE SHOOTING CHART………. 22-25

7. MECHANICAL OF CABINET FRONT DIS-ASSEMBLY...................................... 26

8. SVC_BOM LISTING FOR LGE PART NO ………………………………............. 27-28

9. POWER SYSTEM AND CONSUMPTION CURRENT............................................ 29

10. PCB LAYOUT .....................................................................………………………... 30

11. MAINBOARD SCHEMATIC DIAGRAM ….............................….......…......... 31-36

1. SPECIFICATIONS FOR LCD MONITOR

1-1 General specifications

1. LCD-Panel : Active display area 17 inches diagonal Pixel pitch 0.264 mm x 0.264 mm Pixel format 1280 x 1024 RGB vertical stripe arrangement

2. Display Color : 6-bit, 16.2 million colors

3. External Controls : Power On/Off, Menu-key, Auto key, Left key, Right key OSD menu Controls Contras , Brightness, Auto Center, Focus, Clock , H/V-position , DOS mode select, R/G/B, Color-(7200K,6500K), Languages, Reset

4. Input Video Signal : Analog-signal 0.7Vpp Video signal termination impedance 75 OHM

5. Scanning Frequencies : Horizontal: 30 KHz - 83 KHz Vertical: 55 Hz – 75 Hz Pixel clock: 135 MHz

6. Factory Preset Timing : 17 User Timings : 13 Input signal tolerance : H tolerance ± 1 K, V tolerance ± 0.5 Hz

7. Input Power Source : Switching Mode Power Supply AC 100 – 240 V, 50/60 Hz Universal Type

8. Operating Temperature : 5°C - 40°C Ambient Non-operating Temperature : 5°C - 40°C

9. Humidity : Operating : 10% to 85% RH (non-condensing) Non Operating : 5% to 85%RH (38.7℃ maximum wet bulb temperature)

10. Weight : 7.6 kg

11. External Connection : 15Pin D-type Connector, AC power-Cord

12. View Angle : x-axis right/left = 70, y-axis up/down = 45 ,65

13. Outside dimension : Width x H eight x Thickness = 407x 434 x 173 mm

14. Plug and Play : VESA DDC1/DDC2B

15. Power saving : VESA DPMS

LCD MONITOR DESCRIPTION

The LCD MONITOR will contain an main board, an Inverter module, keyboard, External Adapter which house the flat panel control logic, brightness co ntrol logic, DDC and DC-DC conve rsion The Inverter module will drive the backlight of panel . The Adapter will provides the 12V DC-power 4.16 Amp to Main-board,and Inverter module .

Inverter

AC-IN 100v-240v

1-2 Interface Connectors

(A) AC-Power Cable (B) Video Signal Connectors and Cable (C) External Adapter

Main Board or Interface Board

ADAPTER

Monitor Block Diagram

CCFT Drive.

Keyboard

Flat Panel and CCFL backlight

HOST Computer

RS232 Connector For white balance adjustment in factory mode

Video signal, DDC

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 betwee n two glass plates is kept perfectly even to mai ntain 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) P lease consider t hat 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℃-40℃

without the exposure of sunlight and to keep the humidity less than 85% 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 6.5mA, and the lamp starting voltage was around 1650V, at Ta=25℃)

3. OPERATING INSTRUCTIONS

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

1. Position the display on the desired operation and plug–in t he 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:

11 15

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 signal s 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 follo wing 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.

4. ADJUSTMENT

4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS

Adjustments should be undertaken only on following function : Contras , Bri ght ness, Black level,

Phase, Clock , H/V-po sition , Languages, Color-(7200,6500,User), Auto level, OSD-position, Languages, Reset

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 w arm up before proceeding white balance adjustment.

Before started adjust white balance ,please setting the Chroma-7120 MEM. Channel 1 to 7200 color and MEM. channel 2 to 6500 color, ( our 7200 parameter is x = 302 ±20, y = 319 ±20, Y = 200 ±20cd/m2

and 6500 parameter is x = 313 ±20, y = 329 ±20, Y = 200 ±20 cd/m

How to setting MEM.channel you can reference to chroma 7120 user guide or simple use “ SC” key and “ NEXT” key to modify x,yY value a nd use “ID” key to modify the TEXT description

)

Following is the procedure to do white-balance adjust

Press MENU button during 1 seconds along with plug in the DC-power cord will activate the factory mode, and the OSD screen will located at

I. Bias (Low luminance) adjustment :

1. Press “ AUTO” button , and wait for message “ Pass”

2. Set the contrast on OSD window to the value=45 , color (user )R,G,B set to “50”

3. adjust the brightness on OSD until chroma 7120 measurement reach the value Y=240 cd/m

cd/m

left top of panel.

±10

II. Gain adjustment :

a. adjust 7200 color-temperature

1. Set the Contrast of OSD function to 45 and Adj ust Brightness to chroma 7120 Y=240 ±5 cd/m

2. Switch the chroma-7120 to RGB-mode (with press “MODE” button )

3. Switch the MEM.channel to Channel 01 ( with up or down arrow on chroma 7120 )

4. The lcd-indicator on chroma 7120 will show x = 302 ±10, y = 319 ±10, Y = 200 ±5 cd/m

5. Adjust the Color(user)Mode: RED on OSD window, until chroma 7120 indicator reached the value

R=100

6. Adjust the Color(user)Mode: GREEN on OSD window, until chro ma 7120 indicator reached the value

G=100

7. Adjust the Color(user)Mode: BLUE on OSD window, until chroma 7120 indicator reached the value

B=100

8. repeat above procedure ( item 5,6,7) until chroma 7120 RGB value meet the torlence =100±2

9. switch the chroma-7120 to xyY mode With press “MODE” button

10. Press Color (7800) on OSD window to save the adjustment result

b. adjust 6500 color-temperature

1 Set the Contrast of OSD function to 45 and Adjust Brightness to chroma 7120 Y=240 ±5 cd/m

2 Switch the chroma-7120 to RGB-mode (with press “MODE” button ) 3 switch the MEM.channel to Channel 02 ( with up or down arrow on chroma 7120 ) 4 The lcd-indicator on chroma 7120 will show x = 313 ±10, y = 329 ±10, Y = 200 ±5 cd/m

5 Adjust the Color(user)Mode: RED on OSD window, until chroma 7120 indicator reached the value

R=100

6 Adjust the Color(user)Mode: GREEN on OSD window, until chroma 7120 indicator reached the

value G=100

7 Adjust the Color(user)Mode: BLUE on OSD window, until chroma 7120 indicator reached the value

B=100

8 repeat above procedure ( item 5,6,7) until chroma 7120 RGB value meet the tolence =100±2 9 switch the chroma-7120 to xyY mode W ith press “MODE” button

10 Press Color(6500) on OSD window to save the adjustment result

Turn the POWER-button off to on to quit from factory mode ( in USER-mode, the OSD window location was placed at middle of screen)

2. Clock adjustment Set the Chroma at pattern 63 (cross-talk pattern) or WIN98/95 shut-down mode (dot-pattern). Adjust until the vertical-Stripe-shadow as wide as possib le 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 will see the horizontal interference on screen ,we only find this phenomena in crosstalk pattern or dot pattern , other pattern the affect is very light

4. H/V-Position adjustment Set the Chroma to 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. LANGUAGE function There have 5 language for sel ection, pre ss “MENU” to selected and confirm , press “ LEFT” or “ RIGHT” to change the kind of language ( English , Deutch , Francais, Espanol, It alian)

6. Reset function Clear each old status of auto-configuration and re-do auto-configuration ( for all mode)

This function also recall 7200 color-temperature , if the monitor status was in “ Factory-mode” this reset function will clear Power-on counter ( backlight counter) too.

7. OSD-LOCK function Press Left & Right key during switching on the monitor, the access to the OSD is locked, user only has access to “ Contrast, Brightness, Auto-key “. If the opera tor pressed the Left & Right during switching on the monitor agai n , the OSD is unlocke d.

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 Left/Right button : select function or do an adjustment. MENU button : to activate the OSD window or to confirm the desired function

5. CIRCUIT-DESCRIPTION

5-1 SPECIAL FUNCTION WITH PRESS-KEY

A). press Menu button during 2 seconds al ong with plug-in the DC Power cord:

That operation will set the monitor into “Factory- mode”, in Factory mode we can do the White balance adjustment with RS232 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.

B). Press both Left & Right button along with Power button off to on once will activate the OSD-LOCK

function, repeat this procedure will disable OSD-LOCK

In OSD-LOCK function, all OSD function will be lock , except Contrast and Brightness

OSD-INDEX EXPLANATION

1. CABLE NOT CONNECTED: Signal-cable not connected.

2. INPUT NOT SUPPORT:

a. INPUT frequency out of range: H > 83kHz, v > 75Hz or H < 28kHz, v < 55Hz b. INPUT frequency out of VESA-spec. (out of tolerance too far)

5-2 CIRCUIT FUNCTION DESCRIPTION

USE for computer graphics images to convert analog RGB data to digital data with interpolation process, zooming, generated the OSD font , perfor m overlay function and generate drive-timing for LCD-PANEL.

Use for calculate frequency, pixel-dot , detect change mode, rs232-communication, power-consumption control, O S D-index warning , …etc.

EEPROM type, 1K ROM-SIZE, for saving DDC-CONTENT.

EEPROM type, 16K ROM-SIZE, for saving AUTO-config data, White-balance data, and Power-key status and Backlight-counter data.

7. U905,RT9164(Linear regulator 5V to 2.5V)

8. U600,U601,LVDS ( use NOVATEK NT7181F)

Convert the TT L signal to L VDS signal , the advantage o f LVDS signal is : the wire c an be lengthe n and eliminate wire number , low EMI .LVDS signal is high frequency but low voltage, only 0.35 VPP ,the frequency is seven times hi gher than TT L

9. U401, 74F14D(Schmitt triggger) The 74F14 contains six logic inverters which accept standard TTL input signals and provide standard TTL Output levels

1. U200,GMZAN2 ( all-in-one chip solution for ADC, OSD, scalar and interpolation) :

2. U302,89C51RD2 (PHILIPS- MCU, type 8052 series with 64k Rom-size and 512 byte ram) :

3. U203,24LC21 (MicroChip IC) :

4. U300,24C16 (ATMEL IC) :

5. U304,LM2569S( NS brand switching regulator 12V to 5V with 3A load current) .

6. U305,AIC 1084-33CM (AIC brand linear regulator 5V to 3.3V)

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