Daewoo L520B User manual

DAEWOO ELECTRONICS CO., LTD.
http ://svc.dwe.co.kr
Service Manual
XGA COLOR MONITOR
Model :
L520B/L520BM
L521B/L521BM
L520BAV
October, 2002

CONTENTS
SAFETY PRECAUTIONS 1
GENERAL SAFETY INFORMATION 2
SERVICING PRECAUTIONS 3
TECHNICAL INFORMATION 6
GENERAL INFORMATION 7
PIN CONNECTOR 8
CAUTIONS FOR ADJUSTMENT AND REPAIR 8
OPERATION & ADJUSTMENT 9
ALIGNMENT PROCEDURE 21
TROUBLESHOOTING HINTS (L520B/L520BM/L521B/L521BM) 22
TROUBLESHOOTING HINTS (L520BAV) 29
BLOCK DIAGRAM 39
SCHEMATIC DIAGRAM 40
EXPLODED VIEW & MECHANICAL PARTS LIST 49
INFORMATION OF PART DESCRIPTION 50
ELECTRICAL PARTS LIST (L520B/L520BM/L521B/L521BM) 51
ELECTRICAL PARTS LIST (L520BAV) 60

1
SAFETY PRECAUTIONS
◆Safety Check
Care should be taken while servicing the inverter that generates the high voltage to lighten CCFL of the
LCD panel.
◆Fire & Shock Hazard
• Insert an isolation transformer between the analog color display and AC power line before servicing the
chassis.
• When servicing, pay close attention to the original lead dress especially in the high voltage circuit area;
if a short circuit is found, replace all parts which have been overheated as a result of the short circuit.
• All the protective devices must be reinstalled per original design.
• Soldering must be inspected for possible cold solder points, frayed leads, damaged insulation, solder
splashes or sharp solder points. Be certain to remove all foreign materials.
CAUTION: No modifications of any circuits should be attempted. Service work should be performed
only after you are thoroughly familiar with all of the following safety checks and servicing
guidelines.

2
GENERAL SAFETY INFORMATION
◆Terms in the manual
CAUTION Statements identify conditions or practices that could result in damage to the equipment or
other property.
WARNING Statements identify conditions or practices that could result in personal injury or loss of
life.
◆Terms as marked on equipment
CAUTION Statements indicate a personal injury hazard not immediately accessible as one reads the
marking or a hazard which is properly included on the equipment itself.
WARNING Statements are clearly concerning indicated personal injury hazards.
◆Symbols in the manual
The symbols indicate where applicable cautionary or other information is to be found.
◆Symbols as marked on equipment
Protective GROUND terminal
◆High Voltage Warning And Critical Component Warning Label
The following warning label is on the inverter isolation case.

3
SERVICING PRECAUTIONS
◆General Servicing Precautions
1. Always unplug the AC power cord from the AC power source before:
a. Removing or reinstalling any component, circuit board, module, or any other instrument assembly.
b. Disconnecting or reconnecting any electrical plug or other electrical connection.
c. Connecting a test substitute in parallel with an electrolytic capacitor in the instrument.
2. Test high voltage only by measuring it with an appropriate high voltage meter or other voltage
measuring device (DVM, FETVOM. etc.) equipped with a suitable high voltage probe. Do not test high
voltage by “drawing an arc”.
3. Do not any spray chemicals on or near this instrument, or any of its assemblies.
4. Unless otherwise specified in this service manual, only clean electrical contacts by applying the
following mixture to the contacts with a pipe cleaner, cotton-tipped stick, or comparable nonabrasive
applicator: 10% (by volume) Aceton and 90% (by volume) isopropyl alchohol (90%-99% strength).
5. Do not apply AC power to this instrument and/or any other of its electrical assemblies unless all the
solid-state device heat sinks are correctly installed.
6. Always connect the test instrument ground lead to the appropriate instrument chassis ground before
connecting the test instrument positive lead. Always remove the test instrument ground lead last.
7. Only use the test fixtures specified in this service manual with this instrument.
CAUTION: Before servicing instruments covered by this service manual, its supplements, and
addendum, please read and follow the SAFETY PRECAUTIONS of this manual.
NOTE: If unforeseen circumstances create conflict between the following servicing precautions and any
of the safety precautions on page 1 of this manual, always follow the safety precautions.
Remember: Safety First.
CAUTION: A wrong part substitution or incorrect polarity installation of electrolytic capacitors
may result in a explosion.
CAUTION: This is a flammable mixture. Unless specified in this service manual, lubrication of
contacts is not required.

4
◆ Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by static electricity.
Such components are commonly called Electrostatically Sensitive (ES) Devices.
The typical examples of ES devices are integrated circuits, some field-effect transistors, and
semiconductor “chip” components. The following techniques should be used to help reduce the incidence
of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly,
wipe off any electrostatic charge on your body by touching any known earth ground. Alternatively,
obtain and wear a commercially available discharging wrist strap device which should be removed for
potential shock reasons prior to applying power to the unit under testing conditions.
2. After removing the electrical assembly equipped with ES devices, place the assembly on a conductive
surface such as aluminum foil to prevent electrostatic charge buildup or exposure to the assembly.
3. Only use a grounded-tip soldering iron to solder or unsolder ES devices.
4. Only use an anti-static type solder removal device. Some solder removal devices not classified as “anti-
static” can generate enough electrical charges to damage ES devices.
5.
Do not use freon-propelled chemicals. These can generate enough electrical charges to damage ES devices.
6. Do not remove a replacement ES device from its protective package until immediately before you are
ready to install it. (Most replacement ES devices are packaged with leads electrically shorted together
by conductive foam, aluminum foil, or comparable conductive material).
7. Immediately before removing the protective material from the leads of replacement ES devices, touch
the protective material to the chassis or circuit assembly into which the device will be installed.
8. Minimize bodily movements when handling unpackaged replacement ES devices. (Otherwise harmful
motion such as the brushing together clothes fabric or the lifting your foot from a carpeted floor can
generate enough static electricity to damage ES devices).
◆ General Soldering Guidelines
1. Use a grounded-tip, low-wattage soldering iron with appropriate tip size and shape that will maintain
tip temperature between a 550°F-660°F (288°C-316°C) range.
2. Use an appropriate gauge of RMA resin-core solder composed of 60 parts tin/40 parts lead.
3. Keep the soldering iron tip clean.
4. Throughly clean the surface to be soldered. Use a small wire-bristle (0.5 inch or 1.25cm) brush with a
metal handle. Do not use freon-propelled spray-on cleaners.
5. Use the following soldering technique:
a. Allow the soldering iron tip to reach normal temperature (550°F to 660°F or 288°C to 316°C)
b. Hold the soldering iron tip and solder strand against the component lead until the solder melts.
c. Quickly move the soldering iron tip to the junction of the component lead and the printed circuit foil,
and hold it there until the solder flows onto and around both the component lead and the foil.
d.
Closely inspect the solder area and remove any excess or splashed solder with a small wire-bristle brush.
CAUTION: Be sure that no power is applied to the chassis or circuit, and observe all other safety
precautions.
CAUTION: Work quickly to avoid overheating the circuit board printed foil.

5
FIGURE 1. USE SOLDERING IRON TO PRY LEADS
◆ IC Removal/Replacement
Some utilized chassis circuit boards have slotted (oblong) holes through which the IC leads are inserted
and then bent flat against the circuit foil. When holes are slotted, the following technique should be used
to remove and replace the IC. When working with boards using the familiar round hole, use the standard
technique as outlined in paragraphs 5 on the page under the title of general soldering guidelines.
◆ Removal
1. Desolder and straighten each IC lead in one operation by gently prying up on the lead with the
soldering iron tip as the solder melts.
2. Draw away the melted solder with an anti-static suction-type solder removal device (or with
desoldering braid before removing the IC.
◆ Replacement
1. Carefully insert the replacement IC in the circuit board.
2. Carefully bend each IC lead against the circuit foil pad and solder it.
3. Clean the soldered areas with a small wire-bristle brush. (lt is not necessary to reapply acrylic coating
to the area).
◆ “Small-Signal” Discrete Transistor Removal/Replacement
1. Remove the defective transistor by clipping its leads as close as possible to the component body.
2. Bend the ends of each of three leads remaining on the circuit board into a “U” shape.
3. Bend the replacement transistor leads into a “U” shape.
4. Connect the replacement transistor leads to the corresponding leads extending from the circuit board
and crimp the “U” with long nose pliers to ensure metal-to-metal contact, then solder each connection.
◆ Power IC, Transistor or Devices Removal/Replacement
1. Heat and remove all solders from the device leads.
2. Remove the heatsink mounting screw (if applicable).
3. Carefully remove the device from the circuit board.
4. Insert new device in circuit board.
5. Solder each device lead and then clip off excess lead.
6. Replace heatsink.

6
◆ Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as possible to diode body.
2. Bend the two remaining leads perpendicularly to the circuit board.
3. Observing diode polarity, wrap each lead out of the new diode around the corresponding lead on the
circuit board.
4. Securely crimp each connection and solder it.
5. Inspect the solder joints of the two “original” leads on the circuit board copper side. If they are not
shiny, reheat them and apply additional solder if necessary.
TECHNICAL INFORMATION
Panel Size 15-inch (38cm) diagonal
Pixel Pitch 0.297 x 0.297 mm
Viewing Angle 60°(Right/Left)
40°(up), 60°(down)
Contrast Ratio 350:1 contrast ratio (typ)
Brightness 250cd/m2brightness(typ)
Color Filter RGB vertical stripe
Synchronization Horizontal 30 - 62 KHz
Vertical 50 - 75 Hz
Video Bandwidth 80 MHz
Max Resolution 1024 x 768 75Hz
Optimal Resolution 1024 x 768 60Hz
Colors 6bit (16.7M Colors)
Display Area 304.1 mm x 228.1 mm
PC Input Signal Sync H/V separate (TTL)
Video 15 pin mini D-sub(Analog RGB)
DVI-D(Option)
AV Input Signal Video CVBS(RCA), S-Video(Mini-DIN)
(L520BAV only) Audio RCA Left+Right Input
Stereo Mini Jack Input & Output
TV Receiving Signal TV Tuner NTSC, PAL
(Option)
External Speaker Output 4W(Left 2W+Right 2W)
(L520BM/L521BM/L520BAV only)
Plug and Play VESA DDC Compatible
Power Source 100-240Vac, 50/60Hz (Free Voltage)
Power Consumption 26 W(without speaker)
Dimension-W x H x D 370 x 352 x 205 mm(with stand)
(without speaker) 370 x 312 x 60 mm(without stand)
Weight-net/gross 4.2 / 5.5 Kg (9.2 / 12.1 lbs)
Power Saving EPA, VESA DPMS, Nutek Compliant
Tilt Range 5° forward, 30° backward
Operating Temperature 10 ~ 40°C /50 ~ 104°F
a
a

7
This TFT LCD monitor automatically scans all horizontal frequencies from 30KHz to 62KHz, and all
vertical frequencies from 50Hz to 75Hz. This TFT LCD monitor supports IBM PC, PC/XT, PC/AT, personal
System/2 (PS/2), Apple Macintosh, and compatible users crisp text and vivid color graphics display when
using the following graphics adapters : (VGA, Super VGA, VESA and XGA and Apple Macintosh Video
Card). And so, this TFT LCD monitor has a maximum horizontal resolution of 1024 dots and a maximum
vertical resolution of 768 lines for superior clarity of display.
By accepting analog signal inputs which level is zero to 0.7 Volts. This TFT LCD monitor can display and
262, 144 colors depending on the graphics adapter and software being used. (available used to 8 bit panel is
16.7M colors)
◆ Abbreviations
ADJ Adjustment
AFC Automatic Frequency Control
TFT-LCD Thin Film Transistor Liquid Crystal Diplay
CCFL Cold Cathode Fluorescent Lamp
H.SYNC Horizontal Synchronization
OSC Oscillator
P.S.U Power Supply Unit
PWA Printed Circuit Board Wiring Assembly
R.G.B Red, Green, Blue
V.Sync Vertical Synchronization
ADC Analog Digital Converter
GENERAL INFORMATION

8
Arrangement of 15-pin D-sub connector
Pin Signal
1 Red
2 Green
3 Blue
4 GND
5 GND
6 GND - Red
7 GND - Green
8 GND - Blue
9+5Vdc
10 GND - H.Sync
11 GND - V.Sync
12 Bi-directional Data (SDA)
13 Horizontal Sync
14 Vertical Sync (VCLK)
15 Data Clock (SCL)
1
610
15
PIN CONNECTOR
• The white balance adjustment has been done by a color analyzer in factroy. The adjustment procedure,
described in the service manual is made by a visual check.
• Allow 20 minutes warm-up time for the display before checking or adjusting only electrical
specification or function.
• Reform the leadwire after any repair work.
◆ Caution For Servicing
• In case of servicing or replacing inverter, high voltage sometimes remains in the output of the inverter.
Completely discharge high voltage before servicing or replacing inverter to prevent a shock to the
serviceman.
CAUTIONS FOR ADJUSTMENT AND REPAIR

9
Control Panel
<< L520B/L520BM >>
OPERATION AND ADJUSTMENT
moves cursor to the right or low
window in the OSD window and
increases the value of any selected
function.
MENU EXIT
AUTO
swithes the monitor on and off. shows both normal operation and power
management status with power indicator
light.
POWER Indicator
POWER
1
1
3
3
4
4
5
5
6
6
7
7
2
2
moves cursor to the left or high window
in the OSD window and decreases
value of any selected function.
turns the OSD window on and moves
from top menu to sub menu in the OSD
window.
turns the OSD (On-Screen Display)
window off and moves from sub menu
to top menu in the OSD window.
launches the AUTO
TRACKING function
directly.
*
( ) *
( )
*
( )
*
( ) : Hot Key

10
Key Process
HOT KEY
OSD OFF
MENU
EXIT
EXIT EXIT
OSD
OSD
SHARPNESS SHARPNESS
UT L TY
UT L TY UT L TY
1024X768 60K 75
MENU MENU
AUTO TRACKING
BRIGHTNESS
When there is no OSD, if you press this AUTO button, you can
use the best display performance fit for a current mode.
When there is no OSD, if you press this BRIGHTNESS button,
you can adjust the brightness directly.
: decreases brightness
: increases brightness

11
AUTO EXIT MENU BRIGHTNESS
1
76 453
2
Control Panel
<< L521B/L521BM >>
moves cursor to the right or low
window in the OSD window and
increases the value of any selected
function.
MENU EXIT
AUTO
swithes the monitor on and off. shows both normal operation and power
management status with power indicator
light.
POWER Indicator
POWER
1
34
56
7
2
moves cursor to the left or high window
in the OSD window and decreases
value of any selected function.
turns the OSD window on and moves
from top menu to sub menu in the OSD
window.
turns the OSD (On-Screen Display)
window off and moves from sub menu
to top menu in the OSD window.
launches the AUTO
TRACKING function
directly.
*
( ) *
( )
*
( )
*
( ) : Hot Key

12
OSD OFF
OSD
OSD
SHARPNESS SHARPNESS
UT L TY
UT L TY UT L TY
1024X768 60K 75
MENU
MENU MENU
EXIT
EXIT
EXIT
When there is no OSD, if you press this AUTO button, you can
use the best display performance fit for a current mode.
When there is no OSD, if you press this BRIGHTNESS button,
you can adjust the brightness directly.
: decreases brightness
: increases brightness
AUTO TRACKING
AUTO
BRIGHTNESS
Key Process
HOT KEY

/
13
Control Panel
<< L520BAV >>
swithes the monitor on and off. shows both normal operation and power
management status with power indicator
light.
POWER Indicator
POWER
12
34567
21
MENU
34
5
moves cursor to the right or low window
in the OSD window and increases the
value of any selected function.
moves cursor to the left or high window
in the OSD window and decreases value
of any selected function.
turns the OSD window on and moves
from top menu to sub menu in the OSD
window.
EXIT
6
AUTO
7launches the AUTO TRACKING
function directly.
turns the OSD (On-Screen Display)
window off and moves from sub menu
to top menu in the OSD window.
*
( )
*
( )
*
( )
*
( ) : Hot Key
SOURCE
selects input signal
(PC/SVIDEO/VIDEO/SOUND).

14
When there is no OSD, if you press this AUTO button, you can
use the best display performance fit for a current mode.
When there is no OSD, if you press this BRIGHTNESS button,
you can adjust the brightness directly.
: decreases brightness
: increases brightness
Key Process
HOT KEY
AUTO TRACKING
AUTO
BRIGHTNESS
OSD OFF
MENU
EXIT
EXIT EXIT
OSD
OSD
SHARPNESS SHARPNESS
UT L TY
UT L TY UT L TY
1024X768 60K 75
MENU MENU

15
Adjustment Procedure
Adjust the CLOCK
control.
Perform the AUTO
POSITION.
Is the H.Size
proper?
Is the
noise displayed on
the screen?
Perform the AUTO
TRACKING.
Is the
noise displayed on
the screen yet?
Is the
noise displayed on
the screen yet?
Adjust the CLOCK FINE
until the screen is
cleared.
Yes
Yes
Yes
Yes
No
No
No
No End

16
Display horizontal & vertical frequency and polarity.
STATUS
Reset the screen to the Factory Preset Display Settings.
RECALL
AUTO POSITION Choose automatically the proper horizontal position and vertical
position & size of the screen image.
CONTRAST Adjust the contrast of image, the difference between light and dark
areas on the screen.
Adjust the display OSD Menu.
OSD
TIME OUT
AUTO TRACKING Adjust the horizontal & vertical picture image quality and size.
Select language for OSD (6 languages).
LANGUAGE
Adjust the position of the display horizontally(left or right) and
vertically (up or down).
H. CENTER &
V. CENTER
Choose different preset color temperatures or set your own customized
color parameters.
Adjust the width (horizontal size) of the screen image.
Sharpen the focus by aligning the illuminated pixels and adjust until the
screen image looks focused, crisp and sharp. Adjusting the CLOCK
FINE after the CLOCK adjustment will produce a clear screen.
Adjust the red color.
COLOR
TEMPERATURE
CLOCK
CLOCK FINE
RED CONTROL
Adjust the green color.
Adjust the blue color.
GREEN CONTROL
BLUE CONTROL
ICON CONTROL FUNCTIONS
R
G
B
Adjust the display image quality (if the screen proceed to scaling up).
SHARPNESS
Adjust the OSD position horizontally (left or right) and vertically (up or
down).
OSD POSITION
OSD
OSD Functions (L520B/L520BM/L521B/L521BM)

17
Adjust the red color.
CLOCK
Increase or decrease audio volume.
VOLUME
Balance audio sound.
BALANCE
Adjust high frequency response.
Adjust low frequency response.
TREBLE
BASS
AUTO TRACKING Adjust the horizontal & vertical picture image quality and size.
Adjust the width (horizontal size) of the screen image.
CLOCK
R
G
Sharpen the focus by aligning the illuminated pixels and adjust until the screen
image looks focused, crisp and sharp. Adjusting the CLOCK FINE after the
CLOCK adjustment will produce a clear screen.
Adjust the green color.
CLOCK FINE
RED CONTROL
GREEN
CONTROL
COLOR
;
OSD Functions (L520BAV)
<< OSD FUNCTIONS WITH USING PC >>
INPUT
Select PC mode.
PC
Select S-VIDEO mode.
SVIDEO
Select Video(CVBS) mode.
VIDEO
Adjust sound.
SOUND

18
CONTRAST
Adjust the display image quality (if the screen proceed to scaling up).
SHARPNESS
Select language for OSD (6 languages).
LANGUAGE
Adjust the OSD position horizontally (left or right) and vertically (up or down).
OSD POSITION
OSD
Reset the screen to the Factory Preset Display Settings.
RECALL
Choose automatically the proper horizontal position and vertical position & size
of the screen image.
AUTO POSITION
Display horizontal & vertical frequency and polarity.
STATUS
OSD TIME OUT Adjust the display OSD Menu.
UTILITY
Adjust the contrast of image, the difference between light and dark areas on the
screen.
CONTRAST
Adjust the blue color.
B
Choose different preset color temperatures or set your own customized color
parameters.
COLOR
TEMPERATURE
Adjust the position of the display horizontally (left or right) and vertically (up or
down).
BLUE CONTROL
H. CENTER &
V. CENTER
CENTER