Daewoo L500B User manual

Service Manual
TFT LCD MONITOR
Model : L500B
DAEWOO ELECTRONICS CO., LTD
OVERSEAS SERVICE DEPT.

1
TABLE OF CONTENTS
SAFETY PRECAUTIONS ................................................................................................. 2
GENERAL SAFETY INFORMATION.................................................................................. 3
SERVICING PRECAUTIONS........................................................................................... 4
GENERAL INFORMATION............................................................................................. 8
PIN CONNECTOR ....................................................................................................... 9
OPERATION & ADJUSTMENT ........................................................................................ 10
ALIGNMENT PROCEDURE............................................................................................ 14
TROUBLE SHOOTING HINTS.......................................................................................... 15
BLOCK DIAGRAM ....................................................................................................... 22
PCB LAYOUT ............................................................................................................... 23
SCHEMATIC DIAGRAM................................................................................................ 25
EXPLODED VIEW & MECHANICAL PARTS LIST................................................................ 33
INFORMATION OF PART DESCRIPTION ......................................................................... 34
ELECTRICAL PARTS LIST................................................................................................ 35

2
CAUTION
No modifications of any circuit should be attempted. Service work should only be performed after you
are thoroughly familiar with all of the following safety check and servicing guidelines.
u Fire & Shock Hazard
wIn servicing, pay attention to original lead dress especially in the high voltage circuit. if a short circuit
is found, replace all parts which have been overheated as a result of the short circuit.
wAll the protective devices must be reinstalled per original design.
wSoldering 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.
u Implosion Protection
TFT LCD in this monitor employs integral implosion protection system, but care should be taken to avoid
damage and scratching during installation.
Use only same type replacement TFT panel.
IMPORTANT SAFETY NOTICE
There are special components used in analog TFT LCD color display, which are important for safety.
These parts are shaded on the schematic diagram and on the replacement parts list. It is essential
that these critical parts should be replaced with manufacturer’s specified parts to prevent X-radiation,
shock, fire or other hazards. Do not modify the original design without getting a written permission
from DAEWOO ELECTRONICS CO. or this will void the original parts and labor warranty.
SAFETY PRECAUTIONS

3
GENERAL SAFETY INFORMATION
u 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.
u Terms as marked on equipment
CAUTION Statements indicate a personal injury hazard not immediately accessible as one reads the
marking, or a hazard to properly including the equipment itself.
WARNING Statementsindicatea personalinjury hazardimmediatelyaccessible asonereads themarking
u Symbols in the manual
This symbol indicates where applicable cautionary or other information is to be found.
u Symbols as marked on equipment
Protective GROUND terminal
u High Voltage Warning And Critical Component Warning Label
Following warning label is on the backlight outside.
WARNING
This product includes critical mechanical and electrical parts. For continued safety, replace critical
components indicated in the service manual only with exact replacement parts given in the parts list.
Refer to service manual for measurement procedures and proper service adjustments.

4
SERVICING PRECAUTIONS
CAUTION
Before servicing instruments covered by this service manual, its supplements and addendum, 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.
u 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.
CAUTION
A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result in a
explosion hazard.
2. Do not any spray chemicals on or near this instrument or any or its assemblies.
3. Unless specified otherwise in this service manual, 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).
CAUTION
This is a flammable mixture. Unless specified otherwise in this service manual, lubrication of contacts
is not required.
4. Do not apply AC power to this instrument and/or any of its electrical assemblies unless all solid-state
device heat sinks are correctly installed.
5. 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.
6. Use only the test fixtures specified in this service manual with this instrument.
CAUTION
Do not connect the test fixture ground strap to any heatsink in this instrument.

5
SERVICING PRECAUTIONS
u Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by static electricity.
Such components commonly are called Electrostatically Sensitive (ES) Devices.
The examples of typical 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,
drain off any electrostatic charge on your body by touching a 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 test.
2. After removing an electrical assembly equipped with ES devices, place the assembly on a conductive
surface such as aluminum foil to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.
4. Use only 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 a replacement ES device,
touch the protective material to the chassis or circuit assembly into which the device will be installed.
CAUTION
Be sure that no power is applied to the chassis or circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged replacement ES devices. (Otherwise harmful
motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted
floor can generate enough static electricity to damage an ES devices).
u General Soldering Guidelines
1. Use a grounded-tip, low-wattage soldering iron with appropriate tip size and shape that will maintain
tip temperature within 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 only 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
Work quickly to avoid overheating the circuit board printed foil.

6
SERVICING PRECAUTIONS
FIGURE1. USE SOLDERING IRON TO PRY LEADS
u 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.
u Removal
1. Desolder and straighten each IC lead in one operation by gently prying up on the lead with the solder-
ing iron tip as the solder melts.
2. Draw away the melted solder with an anti-static suction-type solder removal device (or with desolder-
ing braid before removing the IC.
u 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).
u “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 end 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 insoure metal-to-metal contact, then solder each
connection.

7
SERVICING PRECAUTIONS
u 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 clip off excess lead.
6. Replace heatsink.
u 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.
uTECHNICAL INFORMATION
Electrical
Pixel pitch 0.3mm X 0.3mm
Horizontal frequency 30KHz to 62KHz (Automatically)
Vertical frequency 50Hz to 85Hz (Automatically)
Operating temperature 10-40°C / 50-104°F
Operating humidity 8-80%
Mechanical
Cabinet Molded Plastic Cabinet with attachable tilt & swivel base
Dimension (set with packing) 502(H) X 502(W) X 242(D) mm
Weight(net) 4.5 Kg
Controls Power Switch
OSD control

8
GENERAL INFORMATION
This TFT LCD monitor automatically scans all horizontal frequencies from 30KHz to 62KHz, and all verti-
cal frequencies from 50Hz to 85Hz. 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)
u Abbreviations
ADJ
AFC
H.sync
OSC
P.S.U
PWA
R.G.B
V.sync
Adjustment
Automatic Frequency Control
Horizontal Synchronization
Oscillator
Power Supply Unit
Printed Circuit Board Wiring Assembly
Red, Green, Blue
Vertical Synchronization

9
PIN CONNECTOR
u CAUTION FOR ADJUSTMENT AND REPAIR
wThe white balance adjustment has been done by a color analyzer in factroy. The adjustment proce-
dure, described in the service manual is made by a visual check.
wAllow 20 minutes warm-up time for the display before checking or adjusting only electrical specifica-
tion or function.
wReform the leadwire after any repair work.
Pin Signal
1Red
2Green
3Blue
4GND
5GND
6GND - Red
7GND - Green
8GND - 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)
Arrangement of 15-pin D-sub connector
1
6
15
10

10
OPERATION & ADJUSTMENT
u Control Panel
wMove cursor to the right window on the OSD window.
wIncrease the value of any selected function.
wMove cursor to the left window on the OSD window.
wDecrease the value of any selected function.
wLaunch OSD(On-Screen Display) MENU window.
wMove cursor to the high window on the OSD window.
wIncrease the value of V.center.
wMove cursor to the low window on the OSD window.
wDecrease the value of V.center.

11
OPERATION & ADJUSTMENT
u Key Process
wWhen you choose the icon on the OSD window, you can exit the OSD screen.
u Hot Key
R
G
B
Start

12
OPERATION & ADJUSTMENT
u Adjustment procedure
Is the mode
1024x768?
Is the H.Size
proper?
Is the
noise displayed on
the screen?
Is the
noise displayed on
the screen?
Is the
noise displayed on
the screen yet? End
Adjust the FIT SCREEN.
Perform the
Adjust the
until the screen is cleared.
AUTO TRACKING.
Perform the
AUTO POSITION.
Adjust the control.
CLOCK
CLOCK FINE
Yes
No
No
No
NoYes

13
OPERATION & ADJUSTMENT
u OSD Functions
ICON CONTROL FUNCTIONS
LANGUAGE Select language for OSD (5 languages).
CLOCK Adjust the width (horizontal size) of the screen image.
CLOCK FINE
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.
COLOR TEMP
Choose different preset color temperatures or set your own customized
color parameters.
RED CONTROL Adjust the red color.
GREEN
CONTROL
Adjust the green color.
BLUE CONTROL Adjust the blue color.
H.CENTER &
V.CENTER
Adjust the position of the display horizontally (left or right) and vertically
(up or down).
FIT SCREEN
Make characters of displayed text easier to read (only for resolutions
lower than 1024x768).
SMART
SCALING
Adjust the display image quality (if the screen proceed to scaling up).
AUTO
TRACKING
Adjust the horizontal & vertical picture image quality and size.
OSD
TIME OUT
Adjust the display OSD Menu.
STATUS Display horizontal & vertical frequency and polarity.
RECALL
Reset the screen to the Factory Preset
Display Settings.
AUTO
POSITION
Choose automatically the proper horizontal position and vertical position
& size of the screen image.

14
ALIGNMENT PROCEDURE
u Standard Check point
1. Power source : 100-240Vac 50/60Hz
2. Aging: Take at least 20 minutes warm up time.
3. Signal
Video input :Analog 0.7Vpp 75Ωterminal positive polarity
Synchronizing : acceptable negative or positive at TTL level
Resolution
Horizontal : 1024 max.
Vertical : 768 max.
Frequency
Horizontal :30KHz - 62KHz
Vertical : 50Hz - 85Hz (available only non interlace mode)
u Adjustment
1. Smart scaling set to 50%.
2. Contrast set to 100%.
3. Brightness set to 50%.
4. Switching to factory alignment mode
Press power key with down menu key( t) at the power off status.
5. Video level adjustment
Receive stair pattern of 16 step (doesn’t care any mode).
Readjust coarse R, G, B in TDA8752 menu before saturation point.
6. Set up the tracking
See the user’s manual at page 8 th.
7. Switching to user’s mode
If turn-off and turn-on then switched to user’s mode.
* All of adjusted data stores by fade out of OSD.

15
TROUBLE SHOOTING HINTS
1. Abnormal mode detect
YES
Abnormal
mode detect
Troublevideo input
circuit.
Check input H. Sync
of TDA8752. NO
YES
Trouble in the TDA8752.
Check
waveformsof #84 pin
of TDA8752
correct?
YES
Troublein the
MX88281.
NO

16
TROUBLESHOOTING HINTS
2. Trouble in Power on
Trouble in power on.
Referto No video
or No raster.
PowerLED. ON
OFF
Troubleinadapter.
Check output
voltage of adapter.
YES
Isthe5VS line
normal?
NO
Troublein SQ8 and its
ambient circuit.
NO
YES
YES
Is the pulse of pin9
of the IC1? Trouble in Q7 or its
ambient circuit.
Trouble in IC2 or its
ambientcircuit.
NO

17
TROUBLESHOOTING HINTS
3. No raster
Noraster.
Trouble in the Q10 or
MX88281 (If it's trouble
inthe MX88282, change
the main B'D)
Check the output
ofthe Q10 or #3pin
of CN1.
< 2.5V
> 2.5V
Check the 12V of the
main power.
CN1 #1 pin
12V check.
YES
Check the DC/AC
output.
NO
Troublein DC/AC
inverter.
NO
YES
Replace LCD panel.

18
TROUBLESHOOTING HINTS
4. One color is missing
YES
One color is missing.
Checkthe output signal
of the MX88281
and 74act573.
IsOSD color
normal? NO
YES
Replace the main B'D.
Arethe R, G,
B digital (8 bit) output
of the U17
(TDA8752)?
YES
Checkvideosignal cable
or video card.
Isinput signal
normal? NO
YES
Troubleinthe
soldering.
NO

19
TROUBLESHOOTING HINTS
5. Pre check
Precheck
Check reset signal
(#9 pin of micom) and
itsambient circuit.
Check output
voltage
(5V/3.3V/12V).
NO
Trouble in the Q9 and
itsambient circuit.
NO
YES
Trouble each trouble item.
Check on/off
signal of micom.
YES
Check output
ofQ9.
YES
Trouble in the SU1.
NO