Daewoo L500B1 User manual

DAEWOO ELECTRONICS CO., LTD.
http ://svc.dwe.co.kr
Service Manual
XGA COLOR MONITOR
Model : L500B1
November, 2000

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 14
TROUBLESHOOTING HINTS 15
BLOCK DIAGRAM 22
PCB LAYOUT 23
SCHEMATIC DIAGRAM 27
EXPLODED VIEW & MECHANICAL PARTS LIST 28
INFORMATION OF PART DESCRIPTION 29
ELECTRICAL PARTS LIST 30

SAFETY PRECAUTIONS
1
◆Safety Check
Care should be taken while servicing this analog color display because of the high voltages used in the
deflection circuits. These voltages are exposed in such areas as the associated flyback and yoke circuits.
◆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.
◆Implosion Protection
Picture tube in this monitor employs intergral implosion protection system, but care should be taken to
avoid damage and scratching during installation.
Only use same type replacement picture tubes.
◆X-Ray
IMPORTANT SAFETY NOTICE: There are special components used in this analog 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-Ray, shock, fire or other hazards. Do
not modify the original design without getting written permission
from DAEWOO ELECTRONICS CO. or this will void the original
parts and labor warranty.
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.
WARNING: The only potential source of X-Ray is the picture tube. However when the high voltage
circuitry is operating properly, there is no possibility of an X-Ray problem. The basic
precaution which must be exercised is to keep the high voltage at the following factory
recommended level.
NOTE: It is important to use an accurate, periodically, calibrated high voltage meter.
• To measure the high voltage, use a high-impedance high-voltage meter.
Connect(-) to chassis and (+) to the CRT anode button.
• Turn the Contrast & Brightness Control fully counterclockwise.
• Measure the high voltage. The high voltage meter should indicate the following factory
recommended levels.
• If the upper meter indication exceeds the maximum level, immediate service is required to
prevent the possibility of premature component failure.
• To prevent X-Ray possibility, it is essential to use the specified picture tube.
• The normal high voltage is 25.5KV or below and must not exceed 29KV at zero beam current
at rated voltage.

GENERAL SAFETY INFORMATION
2
Warning: This product includes critical mechanical and electrical parts which are essential for x ray
protection. For continued safety, replace critical components that are indicated in the service
manual with exact replacement parts given in the parts list.
Operating high voltage with this product is 29Kv at minimum brightness. Refer to service
manual for measurement procedures and proper service adjustments.
◆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 CRT PWB shield case inside the unit.

SERVICING PRECAUTIONS
3
◆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.
d. Discharging the picture tube anode.
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. Discharge the picture tube anode only by: (a) first connecting one end of an insulated clip lead to the
degaussing or line grounding system shield at the point where the picture tube socket ground lead is
connected, and then (b) touching the other end of the insulated clip lead to the picture tube anode
button, using an insulating handle to avoid personal contact with high voltage.
4. Do not any spray chemicals on or near this instrument, or any of its assemblies.
5. 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).
6. Do not damage any plug/socket B+ voltage interlocks with which instruments covered by this service
manual might be equipped.
7. 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.
8. 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.
9. 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.
CAUTION: Do not connect the test fixture ground strap to any heatsink in this instrument.

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.

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 15.1-inch (38cm) diagonol
Pixel Pitch 0.3 x 0.3 mm
Synchronization Horizontal 30 - 62 KHz
Vertical 50 - 85 Hz
Plug and Play DDC1/2B/CI
Power Saving EPA, VESA DPMS, Nutek Compliant
Power Source 100-240 Vac, 50/60Hz (Free Voltage)
DC12V, 3A
Power Consumption 21W(without adapter)/26W(with adapter)
Dimension-W x H x D(net/gross) 390 x 401.5 x 73.5mm /502 x 502 x 242mm
Weight(net/gross ) 4.5/6.4 Kg
9.9/14.1lbs
Tilt/Swivel Range Tilt 5° forward, 30° backward
Swivel ± 90° leftward, rightward
Operating Temperature 10 ~ 40°C /50 ~ 104°F

GENERAL INFORMATION
7
This TFT LCD monitor automatically scans all horizontal frequencies from 30KHz to 62KHz, and all
vertical 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)
◆ Abbreviations
ADJ Adjustment
AFC Automatic Frequency Control
CRT Cathode Ray Tube
Def Deflection
D.Y Deflection Yoke
HVG High Voltage Generator
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

PIN CONNECTOR
CAUTIONS FOR ADJUSTMENT AND REPAIR
• Degaussing is always required when adjusting purity or convergence.
• 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 CRT, high voltage sometimes remains in the anode of the CRT.
Completely discharge high voltage before servicing or replacing CRT to prevent a shock to the
serviceman.
Arrangement of 15-pin D-sub connector
8
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

OPERATION & ADJUSTMENT
9
Control Panel
Hot Key
EXIT
AUTO MENU BRIGHTNESS
•The AUTO button launches the AUTO TRACKING function directly.
•The EXIT button turns the OSD (On-Screen Display) window off.
•This button moves from sub menu to top menu in the OSD window.
•The MENU button turns the OSD window on.
•This button moves from top menu to sub menu in the OSD window.
•The button moves cursor to the left or high window in the OSD window.
•This button decreases the value of any selected function.
•The button moves cursor to the right or low window in the OSD window.
•This button increases the value of any selected function.
AUTO
EXIT
MENU
BRIGHTNESS
BRIGHTNESS
AUTO TRACKING
AUTO BRIGHTNESS

10
Key Process
OSD OFF
MENU
EXIT
EXIT
MENU
EXIT
MENU

11
Adjustment Procedure
Is the mode
1024x768?
Adjust the FIT
SCREEN.
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
Yes
No
No
No
No
No End

12
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.
Make characters of displayed text easier to read (only for resolutions
lower than 1024x768).
FIT SCREEN
Adjust the display OSD Menu.
OSD
TIME OUT
SMART SCALING
AUTO TRACKING
Adjust the display image quality (if the screen proceed to scaling up).
Adjust the horizontal & vertical picture image quality and size.
Select language for OSD (5 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 TEMP
CLOCK
CLOCK FINE
RED CONTROL
Adjust the green color.
Adjust the blue color.
GREEN CONTROL
BLUE CONTROL
ICON CONTROL FUNCTIONS
OSD Functions
R
G
B

13
Self Diagnosis
When the monitor doesn’t display, if you press any key, Self Diagnosis screen is displayed. Self Diagnosis
function checks if the status of the monitor is No Signal or Out of range.
No Signal screen is displayed when the D-Sub signal connector is not connected or
the status of the monitor is on DPMS mode.
Out of Range screen is displayed when the applied frequency is under or over
normal range.
Normal range
(Non-interlaced mode only)
H : 30 - 62 KHz (1024 dot Max)
V : 50 - 85 Hz (768 dot Max)

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)
Adjustment
1. Smart scaling set to 69%.
2. Contrast set to 100%
3. Brightness set to 50%
4. Switching to factory alignment mode
Press power key with Auto key 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 saturaton point.
6. Set up the tracking
See the user’s manual at page 8th.
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.
14
ALIGNMENT PROCEDURE

15
TROUBLESHOOTING HINTS
1. Abnormal mode detect
Is a input
H-sync of ADC
correct?
Abnormal mode
detect
No
No
Yes
Yes
Is waveform
of pin 84 of ADC
correct?
Trouble in the H-sync
input circuit.
Trouble
in ADC.
Trouble
in Scalier.
Yes

16
2. Trouble in Power on
No
No
Yes
Yes
Is 5VS line
normal?
Trouble in U3 & Q1
and its ambient circuit.
Trouble in SQ1 and
its ambient circuit.
Check on U1(scalier)
Is Power LED
on or off?
Off
No
Yes
On
Check the output
voltage
of adapter.
Refer to No video
or No raster.
Trouble
in the adapter.
Is the pulse
of pin 7
of -com.

17
3. No Raster
Is 12V
plugged in pin 1
of CN2?
No
No
Yes
Yes
Is the output of
inverter correct?
Check 12V
line of CN3.
Replace the inverter.
Replace a LCD panal.
< 2.5
> 2.5
Check the
output of Q6 or
pin 3 of CN2. Trouble in Q6 or
pin 3 of -com.

18
4. One color is missing
Is the OSD color
normal?
One color is missing
No
Yes
Check the output
signal of Scalier.
No
Yes
Is the input
signal normal? Check the video signal cable or R,G,B
con-ass’y.
Trouble in the soldering
of R,G,B data lines
from output of ADC
to pin 41 wafer.
Yes
No
Yes
Are the
R,G,B Digital values
(every eight bits) correct
on ADC output
stage?
Check the ambient
circuit of ADC.