Daewoo MON712B Service Manual

Service Manual

XGA COLOR MONITOR Model : 712B

DAEWOO ELECTRONICS CO., LTD OVERSEAS SERVICE 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 OPERATION AND ADJUSTMENT 9 ALIGNMENT PROCEDURE 13 TROUBLESHOOTING HINTS 15 BLOCK DIAGRAM 31 PCB LAYOUT 32 SCHEMATIC DIAGRAM 36 EXPLODED VIEW & MECHANICAL PARTS LIST 39 INFORMATION OF PART DESCRIPTION 40 ELECTRICAL PARTS LIST 41

SAFETY PRECAUTIONS

◆ 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.

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.

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 CRT PWB shield case inside the unit.

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.

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.

◆ 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 “antistatic” can generate enough electrical charges to damage ES devices.

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.

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.

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.

◆ 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

CDT Size 17-inch Diagonal visible image area 16.2-inch Dot Pitch 0.28 mm Synchronization Horizontal 30 - 70 KHz

Vertical 50 - 160 Hz Plug and Play DDC1/2B/CI Power Saving EPA, VESA DPMS, Nutek Compliant Power Source 100-240 Vac, 50/60Hz (Free Voltage) Power Consumption 100W Dimension-W x H x D 420 x 440 x 440mm (set with stand) Weight-unpacked(lbs/Kg) 41.1/16.2 Operating Temperature 10 ~ 40°C /50 ~ 104°F

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

This color monitor automatically scans all horizontal frequencies from 30KHz to 70KHz, and all vertical frequencies from 50Hz to 160Hz. 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 display when using the following graphics adapters : (VGA, 8514/A, Super VGA, VESA and XGA and Apple Macintosh Video Card). And so, this color monitor has a maximum horizontal resolution of 1280 dots and a maximum vertical resolution of 1024 lines for superior clarity of display. By accepting analog signal inputs which level is zero to 0.7 Volts. This color monitor can display and unlimited palette of colors depending on the graphics adapter and software being used.

◆ Abbreviations

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)

• 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 CR T, 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

PIN CONNECTOR

CAUTIONS FOR ADJUSTMENT AND REP AIR

OPERATION AND ADJUSTMENT

Control Panel

• Move cursor to the right window on the OSD window.

• Increase the value of any selected function.

• Move cursor to the left window on the OSD window.

• Decrease the value of any selected function.

• Launch OSD(On-Screen Display) MENU window.

• Move cursor to the high window on the OSD window.

• Increase the value of V.size or V.center.

• Move cursor to the low window on the OSD window.

• Decrease the value of V.size or V.center.

Key Process

•

When you choose the icon on the OSD window, you can exit the OSD screen.

Hot Key

BRIGHTNESS CONTRAST

Start

OSD Functions

Adjust the parallelogram when the screen is leaning left or right.

Adjust the rotation when the screen is tilted left or right (optional).

Adjust the left and right margins of the each corner.

ROTATION

PIN CORNER

PARALLELOGRAM

Adjust the trapezoid of the screen by moving the lines inward or outward.

Adjust the side balance when the sides of the screen are bowed towards left or right.

PIN BALANCE

TRAPEZOID

Degauss the display and restore image quality.

DEGAUSS

Display horizontal & vertical frequency and polarity.

STATUS

ICON CONTROL FUNCTIONS

Adjust the left and right margins for more convex or more concave margins.PINCUSHION

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 red gain.

Adjust the green gain.

Adjust the blue gain.

COLOR TEMP

RED GAIN

GREEN GAIN

BLUE GAIN

Adjust the width (horizontal size) and the height (vertical size) of the display.

H. SIZE &

V. SIZE

Select language for OSD (5 languages).

LANGUAGE

ICON CONTROL FUNCTIONS

Reset the screen to the Factory Preset Display Settings.

RECALL

Adjust the vertical picture moire cancellation.

V. MOIRE

Adjust the horizontal picture moire cancellation.

H. MOIRE

◆

Standard Adjustment Conditions

1. Power source voltage : AC 120V, 60Hz/AC 220V, 50Hz.

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 : 30KHz - 70KHz Vertical Frequency : 50Hz - 160Hz

◆ Pre-Adjustment

1. High Voltage Adjustment Adjust 26K Vdc between Anode cap and ground at a cross hatch pattern of 31.5KHz by using VR 602.

2. H.Size Adjustment

(a) Receive a cross hatch pattern of 60KHz (b) Set the H-Size control to the maximum on OSD menu. (c) Adjust H-Size to oversize by using VR501.

◆ Method to launch the factory mode

Step 1. Push the menu button. Step 2. Push the menu button and contrast plus control button ( ) for 5 times in same time.

◆ Main Adjustment

1. Setting the Controls

Set the value of items as following.

Contrast : Max. (OSD value up to 100) Brightness : Center (Set the OSD value to 50)

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 60KHz 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 VGA mode signal by using the signal generator. (b) Pin balance, Parallelogram are adjusted the best geometric status. (c) Repeat the adjustment at each mode.

5. White Balance Adjustment

(a) Receive a full white pattern of 60KHz mode. (b) Set the bright control and contrast control to the maximum and receive the all black pattern. (c) Adjust the FBT screen VR to get the screen luminosity to 0.8 Ft/L. (d) Select the R, G, B Bias on the OSD menu and adjust the ADJUST +/– key to get the color coordinates in

X=0.281, Y=0.311.

(e) If the screen luminosity is changed, adjust the sub brightness control to get the 0.8 Ft/L screen luminosity.

ALIGNMENT PROCEDURE

(f) Set the brightness control to the center and contrast control to the maximum. (g) Receive a full white pattern. (h) Select the R, G, B gain on the OSD menu and adjust the ADJUST +/– key to get the color coordinates in

X=0.281±0.02, Y=0.311±0.02.

(i) Adjust the sub contrast control to get the screen luminosity to 34 Ft/L.

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.

magnets.

(d) Horizontal red and blue lines are converged by varying the tabs together keeping the angle between

them constant. (e) Apply a yellow cross hatch pattern on the display. (f) Vertical green and red lines are converged by varying the angle between the two tabs of the 6-pole

magnets.

(g) Horizontal green and red lines are converged by varying the tabs together and keeping the angle

between them constant.

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