DAEWOO CMC-518X Service Manual

Service Manual

XGA COLOR MONITOR

Model :CMC-518X

DAEWOOELECTRONICSCO., LTD.

D AEWOO ELECTRONICS CO., LTD. O VERSEAS SER VICE DEPT.

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 OPERA TION & ADJUSTMENT 25 BLOCK DIAGRAM 28 PCB LA YOUT 29 SCHEMA TIC DIAGRAM 33 EXPLODED VIEW DIAGRAM 35 REPLACEMENT PARTS LIST 36 P AR TS LIST 37

SAFETY PRECAUTIONS

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.

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.

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 Xradiation, 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.

X-Radiation

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 recommended 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.

GENERAL SAFETY INFORMATION

T erms 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.

T erms 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 V oltage Warning And Critical Component Warning Label

Following warning label is on the CRT PWB shield case inside the unit.

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.

SERVICING PRECAUTIONS

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.

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.

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).

CAUTION: This is a flammable mixture. Unless specified otherwise in this service manual, lubrication of

contacts is not required.

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: Do not connect the test fixture ground strap to any heatsink in this instrument.

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).

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: Work quickly to avoid overheating the circuit board printed foil.

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. (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.

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.

TECHNICAL INFORMATION

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

–+

EXIT MENUADJUST SELECT

GENERAL INFORMATION

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

PIN CONNECTOR

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 1 1 GND 12 Bi-directional Data (SDA) 13 Horizontal Sync 14 Vertical Sync (VCLK) 15 Data clock (SCL)

Arrangement of 15-pin D-sub 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.

ALIGNMENT PROCEDURE

Standard Adjustment Conditions

1. Power source voltage : 100~240Vac 50/60Hz

2. Aging : Take at least 20 minutes warm-up time.

3. Signals Video : Analog 0.7Vpp 75Ω terminal 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.

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=0.31 1¡ 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.

(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.

Horizontal green and magenta lines are converged by varing the tabs together, keeping the angle between them

(g)

constant.

TROUBLESHOOTING HINTS

Yes

About 45Vpp

Yes

No Character

Are the

Contrast &

Brightness Controls

maximum ?

whole screen

bright?

Is CRT

Cathode (Rk, Gk, Bk)

signal level

normal?

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

Trouble in 8Vdc line of the Main PWB

Check the clamping pulse circuit

clamping pulse

(pin 23 of IC801)

normal?

Check the signal cable

input signal

normal?

Trouble in IC801 and its ambient circuit

Yes

12Vpp

1. No Character

2. No Raster

Refer to trouble in power supply unit.

Yes

Refer to trouble in P.S.U

Heater Voltage

(CRT PWB)

about

6V?

CRT heater

red-hot?

whole screen

bright?

Check

G1 voltage about

-70V?

Is CRT

G2 (screen) voltage

about 560V?

65Vdc line

normal?

Yes

Does

increasing of the

Brightness control level

make screen

bright?

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

RK, GK, BK About 45V p-p

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

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?

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

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?

the Fast

Blanking signal

(IC204 pin12)

normal?

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

11Vp-p

14.5Vp-p

4Vp-p

Yes

B+ line voltage

normal?

Q502 base

waveform

normal?

MODE

VGA S.VGA 54KHz

Trouble in FBT

Refer to trouble in power supply unit

Trouble in power supply circuit

Yes

Trouble in Q501, T501

Q501 and its ambient cirucit

Check the circuit of P.S.U

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)

Q501 Gate

waveform

normal?

IC501 7pin

H.DRV waveform

normal?

IC501 pin 9

voltage about

12V?

Yes

the input H.Sync

correct?

B+ Voltage

72Vdc 89Vdc

121Vdc

6. Unstable Picture

Yes

Trouble in IC501 or its ambient circuit

Unstable

picture

Is the

pulse of pin 15 of

the IC501

correct?

Yes

Check IC201 and its ambient circuit

Is the

pulse of pin 33 of

the IC201

correct?

Yes

Check the IC201 and its ambient circuit

Is the

input H.Sync

correct?

Trouble in Signal Cable or 15P D-Sub Connector

5Vpp

6.1 Horizontal

6-2.Vertical

Yes

Refer to P.S.V

Unstable

picture

Is the

12Vdc

line voltage is

correct?

Yes

Trouble in vertical D.Y

Is the

pulse of pin 4, 6 of

the IC401

correct?

Yes

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

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