Daewoo CMC-518X User manual

Service Manual
XGA COLOR MONITOR
Model :CMC-518X
DAEWOO ELECTRONICS CO., LTD.
OVERSEAS SERVICE DEPT.
Serv
i
ce Manual
DAEWOO ELECTRONICS CO., LTD.

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
ALIGNMENT PROCEDURE 9
TROUBLESHOOTING HINTS 11
OPERATION & ADJUSTMENT 25
BLOCK DIAGRAM 28
PCB LAYOUT 29
SCHEMATIC DIAGRAM 33
EXPLODED VIEW DIAGRAM 35
REPLACEMENT PARTS LIST 36
PARTS LIST 37

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 chassis.
¡In 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.
¡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 integral implosion protection system, but care should be taken to avoid damage
and scratching during installation.
Use only same type replacement picture tubes.
X-Radiation
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.
IMPORTANT SAFETY NOTICE : There are special components used in 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-
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.
WARNING : The only potential source of X-Radiation is the picture tube. However when the high voltage circuitry
is operating properly, there is no possibility of an X-Radiation 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 re-
commended level.
¡If the upper meter indication exceeds the maximum level, immediate service is required to
prevent the possibility of premature component failure.
¡To prevent X-Radiation possibility, it is essential to use the specified picture tube.
¡The nominal high voltage is 25.5KV or below, and must not exceed 29KV at zero beam current
at rated voltage.
SAFETY PRECAUTIONS
1

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 to properly including the equipment itself.
WARNING Statements indicate a personal injury hazard immediately accessible as one reads the marking
Symbols in the manual
This symbol indicates 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
Following warning label is on the CRT PWB shield case inside the unit.
GENERAL SAFETY INFORMATION
2
Warning : This product includes critical
mechanical and electrical parts which are
essential for X radiation safety. For continued
safety, replace critical components indicated
in the service manual only with exact
replacement parts given in the parts list.
Operating high voltage for this product is
25KV at minimum brightness. Refer to
service manual for measurement procedures
and proper service adjustments.

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 or its assemblies.
5. 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 alcohol (90% - 99% strength).
6. Do not defeat 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 of its electrical assemblies unless all 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. Use only the test fixtures specified in this service manual with this instrument.
CAUTION: Before servicing instruments covered by this service manual, its supplements and addenda, 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 hazard.
CAUTION: This is a flammable mixture. Unless specified otherwise 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.
SERVICING PRECAUTIONS
3

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.
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).
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¢-600¢(288¡-316¡) 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. Thoroughly 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¢to 600¢or 288¡to 316¡)
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 :Be sure that no power is applied to the chassis or circuit, and observe all other safety
precautions.
4
CAUTION: Work quickly to avoid overheating the circuit board printed foil.

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. (It 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 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 insure metal-to-metal contact, then solder each connection.
FIGURE 1. USE SOLDERING IRON TO PRY LEADS
5

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.
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.
Electrical
CRT dot pitch 0.28mm dot pitch
Horizontal frequency 30KHz to 54KHz (Automatically)
Vertical frequency 50Hz to 120Hz (Automatically)
Operating temperature 10-40¡/50-104¢
Operating humidity 8-80%
Mechanical
Cabinet Molded Plastic Cabinet with detachable tilt & swivel base
Dimension (set with stand) 381.5(H)x368(W)x394(D) mm
Weight (net) 12.5 Kg
Controls Power Switch
OSD Key
Contrast
Brightness
Horizontal Position
Horizontal Size
Vertical Position
Vertical Size
Pincushion
Trapezoid
R Gain, B Gain
Color Temp
Recall
Degauss
System Spec
6
TECHNICAL INFORMATION
EXIT MENUADJUST SELECT
–+

This color monitor automatically scans all horizontal frequencies from 30KHz to 64KHz, and all vertical frequencies
from 50Hz to 120Hz. This color monitor adopted the OSD (On Screen Display), it shows the sync polarity and
frequency and it provides that easily adjust control. This color monitor supports IBM PC, PC/XT, PC/AT, personal
System/2 (PS/2), Apple Macintosh, and compatible users crisp text and vivid color graphics diaplay when using the
following graphics adapters : (VGA, 8514/A, Supper VGA, VESA and XGA and Apple Macintosh Video Card). And
so, this color 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 color monitor can display an unlimited palette
of colors depending on the graphics adapter and software being used.
Abbreviations
ADJ Adjustment
AFC Automatic Frequency Control
CRT Cathode Ray Tube
Def Deflection
D.Y Deflection Yoke
FBT Flyback Transformer
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
GENERAL INFORMATION
7

Arrangement of 15-pin D-sub connector
¡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.
PIN CONNECTOR
CAUTIONS FOR ADJUSTMENT AND REPAIR
8
Pin Signal
1 Red
2 Green
3 Blue
4 GND
5 GND(Self-Test)
6 GND-Red
7 GND-Green
8 GND-Blue
- No Pin
10 GND-H.Sync
11 GND
12 Bi-directional Data (SDA)
13 Horizontal Sync
14 Vertical Sync (VCLK)
15 Data clock (SCL)
1
610
15

Standard Adjustment Conditions
1. Power source voltage : 100~240Vac 50/60Hz
2. Aging : Takeat least 20 minutes warm-up time.
3. Signals
Video : Analog 0.7Vpp 75Ωterminal positive polarity
Synchronizing : TTL level Negative/Positive Separate/Composite
Deflection frequency
Horizontal Frequency : 30 KHz - 54KHz
Vertical Frequency : 50Hz - 120Hz
Pre-Adjustment
1. B+ Adjustment
Adjust 27.3Vdc¡0.2Vdc between TP1 and ground at 31.5KHz mode, varying VR501.
Main Adjustment
1. Setting the Controls
Set the value of items as following.
Contrast : Max. (OSD value up to MAX)
Brightness : Center (Set the OSD value to center)
2. H.size, V.size, H.phase, V.position, Pincushion, Trapezoid
Receive the cross hatch pattern of Factory preset mode.
H.Size, V.size, H.phase, V.position, Pincushion, Trapezoid are adjusted at each mode.
In Factory, Auto Alignment was done at each mode. Therefore, Factory preset mode has it's
own value according to each control.
3. Focus
(a) Set brightness control to center and contrast control to MAX.
(b) Receive all "H" character pattern of 54KHz mode signal.
(c) Adjust the Focus control of FBT to obtain best Focus (static focus and Dynamic focus).
4. Geometric Distortion Adjustment.
(a) Receive the cross hatch pattern of 54KHz mode signal.
(b) Pin balance, Pin center, Pin corner, Parallelogram are adjusted the best geometric status.
5. White Balance Adjustment
(a) Select 9300¡£K on the OSD Menu.
(b) Receive a cross hatch pattern of 54KHz mode signal by using the signal generator.
(c) Set the brightness control to the center, the contrast control to the maximum and sub contrast
control VR to the center.
(d) Cut off the FBT screen VR.
(e) Set the brightness control to the maximum and receive all the black patterms.
(f) Select the R-BIAS, G-BIAS and B-BIAS on the OSD menu and adjust the DATA +/- key to
get the color coordinates in x=0.281, y=0.311.
(g) Receive al full white pattern.
(h) Select the R-GAIN, G-GAIN and B-GAIN and adjust Data +/- key to get the color coordinates in
x=0.281¡0.05, y=0.311¡0.05
(i) Set the brightness control to the center and adjust the sub contrast control to get the screen
luminosity to 30t/L(a full white pattern over 30Ft/l).
(j) Check if the x,y coordinates of color analyzer is in X=0.281¡0.05, Y=0.311¡0.05.
If the color coordinates is out of range, adjust the R. G. B BIAS & GAIN to get the coorinates in
X=0.281, Y=0.311. Make sure that the coordinates is in range by using contrast control.
ALIGNMENT PROCEDURE
9

(k) Select 6550¡£K on the OSD Menu and set the color coordinates in X=0.313, Y=0.329 at the maximum
contrast control and center brightness control.
(l) Check if the a full white pattern is over 30Ft/L. If you satisfied with the result, readjust the internal sub contrast
VR.
6. Static Convergence Adjustment
(a) Apply a magenta cross hatch pattern on display
(b) Adjust the focus from the best over all focus on the display.
Also adjust the brightness to the desired condition
(c) Vertical red and blue lines are converged by varying the angle between the two tabs of the 4-pole magnets.
(d) Horizontal red and blue lines are converged by varing the tabs together, keeping the angle between them
constant.
(e) Apply a white cross hatch pattern on display.
(f) Vertical green and magenta lines are converged by varing the the angle between the two tabs of the 6-pole
magnets.
(g)
Horizontal green and magenta lines are converged by varing the tabs together, keeping the angle between them
constant.
10

11
1. No Character
TROUBLESHOOTING HINTS
Yes
Yes
No About 45Vpp
Yes
No
No
No Character
Are the
Contrast &
Brightness Controls
maximum ?
Is
whole screen
bright?
Is CRT
Cathode (Rk, Gk, Bk)
signal level
normal?
Is
8Vdc line
normal?
Is the
output signal of the
(pin 15, 19, 22) pre-amp
IC801,
normal?
Rk, Gk, Bk
Change the Contrast &
Brightness control value
to maximum
No Raster
Check the peripheral
circuit of CRT
Check the Video output
circuit and IC801
(pin 2, 4, 6) and
their ambient circuit
Refer to
No Raster
Yes
No
No
Trouble in 8Vdc line
of the Main PWB
Check the clamping
pulse circuit
Is
clamping pulse
(pin 23 of IC801)
normal?
No Check the
signal cable
Is
input signal
normal?
Trouble in IC801 and
its ambient circuit
No
Yes
Yes
Yes
12Vpp

12
2. No Raster
No
No
Refer to trouble in
power supply unit.
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Refer to trouble
in P.S.U
Is
Heater Voltage
(CRT PWB)
about
6V?
Is
CRT heater
red-hot?
Is
whole screen
bright?
Check
G1 voltage about
-70V?
Is CRT
G2 (screen) voltage
about 560V?
Is
65Vdc line
normal?
Yes
Does
increasing of the
Brightness control level
make screen
bright?
No
No
No Raster
Increase the Brightness
& Contrast control level
fully Maxium Trouble in
power supply
circuit
Trouble in
video
circuit
Trouble in
CRT
Trouble in G1
line of Main
PWB
Trouble in FBT
Trouble in 65Vdc
line of power
supply unit
No High Voltage
trouble in FBT
Raster OK

3. A Missing Color
13
No
No
No
No
RK, GK, BK
About 45V p-p
No
Yes
Yes
Yes Yes
0.7Vpp
Check video signal
cable or video card.
Trouble in
IC801 or its
ambient circuit
Trouble in G1 line
and G2 line
One color is
missing
Is
input signal
normal?
Is the
output of pre-amp
IC801,
pin 15, 19, 22
all normal?
CRT
Cathode (Rk, Gk, Bk)
is normal?
Each
grid (G1, G2)
voltage
normal?
Is
video output
Q801, Q831, Q861
waveform
normal?
Trouble in
video output
circuit,
Q803, Q804
Q813, Q814
Q823, Q824
or ambient
Trouble in
65/8 Vdc line
Replace CRT
Yes

4. Abnormal OSD Font
14
No
Yes
Yes
Trouble in IC801
and its ambient
circuit
Trouble in IC204
and its ambient
circuit
Trouble in
IC204 or its
ambient circuit
Abnormal OSD Font
Is menu
key selected?
Is OSD Font
exist?
No
Is
the Fast
Blanking signal
(IC204 pin12)
normal?
No
Yes
Is the
output of IC204
(pin 13, 14, 15)
normal?
Yes
One color is
missing
Refer to Missing Color
* If menu key selected.

5. Horizontal Output Circuit
15
11Vp-p
14.5Vp-p
4Vp-p
Yes
Yes
Yes
Yes
Is
B+ line voltage
normal?
Is
Q502 base
waveform
normal?
MODE
VGA
S.VGA
54KHz
No
No
No
Trouble in FBT
No Refer to trouble
in power supply
unit
Trouble in power
supply circuit
Yes
No
Trouble in Q501, T501
Q501 and its
ambient cirucit
Check the circuit of
P.S.U
No
Trouble in IC501.
Trouble in H.sync line
If the holddown circuit stops the
horizontal oscillator during the check,
turn off the power then turn on again
about 10 seconds later
Trouble in Horizontal
output circuit
(No Raster)
Is
Q501 Gate
waveform
normal?
Is
IC501 7pin
H.DRV waveform
normal?
Is
IC501 pin 9
voltage about
12V?
Yes
Is
the input H.Sync
correct?
B+ Voltage
72Vdc
89Vdc
121Vdc

6. Unstable Picture
6.1 Horizontal
16
Yes
No
Trouble in IC501
or its ambient
circuit
Unstable
picture
Is the
pulse of pin 15 of
the IC501
correct?
Yes
No
Check IC201 and
its ambient circuit
Is the
pulse of pin 33 of
the IC201
correct?
Yes
No
Check the IC201 and
its ambient circuit
Is the
input H.Sync
correct?
Trouble in Signal Cable
or 15P D-Sub Connector
5Vpp

6-2.Vertical
17
Yes
No
Refer to P.S.V
Unstable
picture
Is the
12Vdc
line voltage is
correct?
Yes
No
Trouble in
vertical D.Y
Is the
pulse of pin 4, 6 of
the IC401
correct?
Yes
No
Check the IC401 and
its ambient circuit
Is the output of
pin 12, 13 of IC501
all normal?
Check the IC501 and its
ambient circuit

7. Focus
18
Yes OK
Check
Focus VR in
FBT
Is
Focus
acceptable?
Monitor remains
unfocused
Trouble in Focus
circuit (FBT)
No