Goldstar FB774GЮ, FB774FT Service Manual

COLOR MONIT OR

SER VICE MANUAL

Website:http://biz.LGservice.com

E-mail:http://www.LGEservice.com/techsup.html

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CHASSIS NO. : CA-1 13

MODEL: 774FT

ID LABEL: FB774G-EL

Same looking with New Chassis

Issue Date: MAY 2002

1. PICTURE TUBE

Size : 17 inch (Flat Slot Mask) DefIection Angle : 90° Neck Diameter : 29.1mm Stripe Pitch : 0.24mm Face Treatment : W-ARAS(Anti-Reflection and

Anti-Static Coating)

Internal : Anti-Glare

2. SIGNAL

2-1. Horizontal & Vertical Sync

1) Input Voltage Level: Low=0~1.2V, High=2.5~5.5V

2) Sync Polarity : Positive or Negative

2-2. Video Input Signal

1) Voltage Level : 0 ~ 0.7 Vp-p a) Color 0, 0 : 0 Vp-p b) Color 7, 0 : 0.467 Vp-p c) Color 15, 0 : 0.7 Vp-p

2) Input Impedance : 75Ω

3) Video Color : R, G, B Analog

4) Signal Format : Refer to the Timing Chart

2-3. Signal Connector

15-pin Attached Connector

2-4. Scanning Frequency

Horizontal : 30 ~ 70 kHz Vertical : 50 ~ 160 Hz

3. POWER SUPPLY

3-1. Power Range

AC 100~240V (Free Voltage), 50/60Hz, 2.0A

3-2. Power Consumption

4. DISPLAY AREA

4-1. Active Video Area :

• Max Image Size - 325.4 x 244.1mm (12.91" x 9.61")

• Preset Image Size - 310 x 230 mm (12.20" x 9.06") 4-2. Display Color : Full Colors 4-3. Display Resolution : 1280 x 1024 / 60Hz

(Non-Interlace)

4-4. Video Bandwidth : 110MHz

5. ENVIRONMENT

5-1. Operating Temperature: 10°C ~ 35°C(Ambient) 5-2. Relative Humidity : 10% ~ 90%

(Non-condensing)

5-3. Altitude : 5,000m

6. DIMENSIONS (with TILT/SWIVEL)

Width : 415.0mm (16.34 inch) Depth : 439.0mm (17.28 inch) Height : 435.0mm (17.13 inch)

7. WEIGHT (with TILT/SWIVEL)

Net Weight : 19.2kg (42.34 lbs.) Gross Weight : 22.5kg (49.61 lbs.)

CONTENTS

- 2 -

SPECIFICATIONS ................................................... 2

SAFETY PRECAUTIONS ........................................ 3

TIMING CHART ....................................................... 4

OPERATING INSTRUCTIONS ................................ 5

BLOCK DIAGRAM ................................................... 8

DESCRIPTION OF BLOCK DIAGRAM.....................9

ADJUSTMENT ....................................................... 11

TROUBLESHOOTING GUIDE .............................. 13

PRINTED CIRCUIT BOARD................................... 23

EXPLODED VIEW...................................................26

REPLACEMENT PARTS LIST ............................... 28

PIN CONFIGURATION........................................... 35

SCHEMATIC DIAGRAM......................................... 36

MODE

NORMAL (ON)

STAND-BY

SUSPEND

OFF

H/V SYNC

ON/ON OFF/ON ON/OFF

OFF/OFF

POWER CONSUMPTION

less than 95W less than 15W less than 15W

less than 3W

LED COLOR

GREEN

ORANGE

SPECIFICATIONS

SAFETY-RELATED COMPONENT WARNING!

There are special components used in this color monitor which are important for safety. These parts are marked

on the schematic diagram and the replacement parts list. It is essential that these critical parts should be replaced with the manufacturer's specified parts to prevent X-radiation, shock, fire, or other hazards. Do not modify the original design without obtaining written permission from LG or you will void the original parts and labor guarantee.

CAUTION:

No modification of any circuit should be attempted. Service work should be performed only after you are thoroughly familiar with all of the following safety checks and servicing guidelines.

SAFETY CHECK

Care should be taken while servicing this color monitor because of the high voltage used in the deflection circuits. These voltages are exposed in such areas as the associated flyback and yoke circuits.

FIRE & SHOCK HAZARD

An isolation transformer must be inserted between the

color monitor and AC power line before servicing the chassis.

• In servicing, attention must be paid to the original lead

dress specially 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 the

original design.

• Soldering must be inspected for the cold solder joints,

frayed leads, damaged insulation, solder splashes, or the sharp points. Be sure to remove all foreign materials.

IMPLOSION PROTECTION

All used display tubes are equipped with an integral implosion protection system, but care should be taken to avoid damage and scratching during installation. Use only same type display tubes.

X-RADIATION

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 keep the high voltage at the factory recommended level; the normal high voltage is about 27kV. The following steps describe how to measure the high voltage and how to prevent Xradiation.

Note : It is important to use an accurate high voltage

meter calibrated periodically.

• To measure the high voltage, use a high impedance high voltage meter, connect (–) to chassis and (+) to the CDT anode cap.

• Set the brightness control to maximum point at full white pattern.

• Measure the high voltage. The high voltage meter should be indicated at the factory recommended level.

• If the 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.

CAUTION:

Please use only a plastic screwdriver to protect yourself from shock hazard during service operation.

SAFETY PRECAUTIONS

- 3 -

TIMING CHART

VIDEO

SYNC

MODE

H/V

Sort

H V H V H V H V

Sync

Polarity

+ + + + + +

Frequency

37.50

74.99

46.88

75.01

53.68

85.07

68.677

85.00

Total

Period(E)

26.67

13.335

21.33

13.331

18.63

11.755

14.561

11.764

Video Active

Time(A)

20.32

12.802

16.16

12.798

14.22

11.178

10.836

11.182

Blanking

Time(B)

6.35

0.533

5.17

0.533

4.41

0.577

3.725

0.582

Sync

Duration(D)

2.03

0.080

1.62

0.064

1.14

0.056

1.016

0.044

Back

Porch(C)

0.51

0.026

0.32

0.021

0.57

0.018

0.508

0.014

Front

Porch(F)

3.81

0.427

3.23

0.448

2.70

0.503

2.201

0.524

Resolution

640 X 480

75Hz

800 X 600

75Hz

800X 600

85Hz

1024 X 768

85Hz

- 4 -

- 5 -

REAR VIEW FRONT VIEW

Front Control Panel

OPERATING INSTRUCTIONS

1. Power ON/OFF Button

This button is used to turn the monitor on and off.

2. Power Indicator

This indicator lights up green when the monitor operates normally; in DPMS (Energy Saving) mode, stand-by, suspend, or power off mode - its color changes to orange, and if abnormal or damaging circuit turns out orange blink.

3. SET Button

This button to enter a selection in the on screen display.

4. OSD Select/Adjustment

Use for selecting (highlighting) an OSD icon and adjusting level of the selected menu.

5. OSD Button

This button to enter or exit the on screen display.

See Front Control Panel

Signal Cable

AC Power Socket

Buttons

OSD Button

Power Button Power Indicator

• Brightness and Contrast can be adjusted directly without entering the On Screen Display (OSD) system. Press the buttons to display the menu and then the buttons to adjust the settings. To save all changes, press the OSD button. The Brightness and Contrast functions are also available in the On Screen Display (OSD) menu.

100

SET Button

On-Screen-Display (OSD) Control

To adjust an image size, position, and operating parameters are quick and easy with the On-ScreenDisplay control system, using the OSD button and the Adjustment control button. A quick example is given below to familiarize you with use of the controls.

Example;

Note: (Monitor and PC’s power switch should be ON, with an image or prompt on the screen).

1. Press the OSD Button, then the Main menu of the OSD appears. Display will look like as below:

2. To access a control, use the or Buttons. When the icon you want becomes highlighted, Press the OSD SET Button.

3. Use the Buttons to adjust the item to the desired level.

4. Accept the changes by pressing the SET button.

5. Exit the OSD by pressing the OSD Button.

- 6 -

BRIGHTNESS CONTRAST

100

BRIGHTNESS CONTRAST

100

OSD

SET

OSD

Birghtness

To adjust the screen brightness level.

Contrast

To adjust the image contrast level.

6500K 9300K

To appear the display’s color temperature.

• 6500K : Slightly reddish white

• 9300K : Slightly Bluish white

TEMP

User easily color set without adjustment Red, Green, Blue (R/ G/ B).

RED To set your own color levels. GREEN To set your own color levels. BLUE To set your own color levels.

BRIGHTNESS CONTRAST

COLOR

POSITION

Vertical Position

To move the image up or down.

Horizontal Position

To move the image left or right.

POSITION

Listed below are icons, icon names, and icon descriptions of the OSD menu.

BRIGHTNESS CONTRAST

100

TEMP

RED

GREEN

BLUE

COLOR

6500K 9300K

PRESET

Degaussing

Used to demagnetize the picture to give a more accurate image and color.

Recall

You can use this function to reload the modified parameters for screen display operation,as specified by the user after purhased;Position, Size, Side Pincushion,Side Pincushion Balance, Parallelogram,Trapezoid (These recalled options may differ depending on the mode selected:Preset, User, or New). If you don’t want to recall the monitor to these modified settings, use the ( ) button to select CANCEL and then press the SELECT (or SET) button.

RESET

Return to all factory default settings except "LANGUAGE": Brightness, Contrast, Tilt,Color 9300K, Video Level, OSD Time,Moire (These reset options may differ depending on the mode selected: Preset,User, or New). If you don’t want to reset the monitor, use the ( ) button to select CANCEL and then press the SELECT (or SET) button.

Moire

This item allows you to reduce the moire (Moire is caused by interference Horizontal Scan Line with the periodical dot screen), It is normally OFF (H:0/V:0) The moire adjustments may affect the focus of the screen.. Moire adjustments may shake slightly while the moire reduction function is on.

Purity

Use to adjust the overall purity of the image if the appears uneven.

Tilt

To correct the image rotation.

Side Pincushion

To correct bowing in or out of the image.

Side Pincushion Balance

To correct the balance of both sides bowling.

Parallelogram

To correct the geometric distortion.

Trapezoid

To correct the geometric distortion.

Corner Top

To correct the irregular distortion of the displayed image.

Corner Bottom

To correct the irregular distortion of the displayed image.

- 7 -

SIZE

Vertical Size

To adjust the image height.

Horizontal Size

To adjust the image width.

SIZE

SHAPE

SPECIAL

Video Level

To select voltage level of the video card output - It is

input level of the monitor. Most video cards are 0.7V.

Language

To choose the language in which the control names are displayed. OSD Menus are available in five languages.

OSD TIME

This item lets you adjust the OSD display time.

SETUP

BLOCK DIAGRAM

- 8 -

POWER INPUT

100~240VAC

(50/60Hz)

Line

Filter

Degaussing

Circuit

[ OSD Control ]

SMPS

TRANS

(T901)

SMPS

CONTROL

(IC901)

DPM

CONTROL

CIRCUIT

80V

50V

15V

6.3V

Purity

Control

Circuit

6.3V

15V

PROM

(IC402)

OSD IC

(IC301)

H-Sync Sig

V-Sync Sig

C DATA(SDA)

C CLOCK(SCL)

VIDEO

PRE-AMP

(IC302)

Signal

Cable

VIDEO

MAIN AMP

(IC303)

CUT OFF IC

H/V Sync Processor

( IC701 )

TDA4841

V-OUT

(IC601)

TDA4866J

H-OUT

(Q706)

H-Linearity

Correction

DC/DC Converter

X-RAY

Protection

Circuit

FBT

( T701 )

Dynamic

Focus

Circuit

Auto

Beam

Limit

Vertical Blanking,

Brightness Control

- 160V

40V

15V

D/D Feed Back

15V

MICOM

(IC401)

SCL / SDA

H/V Sync,

PWM Control

12V

15V

175V

DY CDT

Heater ( 6.3V )

H/V

Sync

Screen

Dynamic Focus

Static Focus

H.V

R/G/B

Bias

R/G/B

Contrast

H-DRV

B-DRV

B+

15V

COIL

DEGAUSSING

COIL

Brightness/Contrast

H/V Position

H/V Size

Tilt

SPCC

Pin Balance

Parallelogram

Trapezoid

Corner Top

Corner Bottom

Color

Video Level

Language

OSD Time

Degaussing

Recall

Reset

Moire

Purity

LM1269 LM2469

MTV038-15

(IC 304)

LM2480

TILT

Control

Circuit

6.3V

TILT

COIL

15V

Purity

400V

Voltage

Regulating

Circuit

SET UP

DESCRIPTION OF BLOCK DIAGRAM

- 9 -

1. Line Filter & Associated Circuit

This is used for suppressing noise of power input line flowing into the monitor and/or some noise generated in the monitor flowing out through the power input line. That is to say,this circuit prevents interference between the monitor and other electric appliance.

2. Degaussing Circuit Coil.

The degaussing circuit consists of the degaussing coil,the PTC(Positive Temperature Coefficient) thermistr(TH901),and the relay(RL901).This circuit eliminate abnormal color of the screen automatically by degaussing the shadow mask in the CRT during turning on the power switch.When you need to degaussing in using the monitor,select DEGAUSS on the OSD menu.

3. SMPS(Switching Mode Power Supply).

This circuit is working of 90~264V AC(50/60Hz). The operation procecedure is as below:

1)AC input voltage is rectified and smoothed by the

bridge diodes(D900) and the capacitor.

2)The rectified voltage(DC) is applied to the primary coil of the transform(T901).

3)The control IC(IC901) generates switching pulse to turn on and off the primary coil of the transformer(T901) repeatedly.

4)Depending on turn ration of the transformer,the secondary voltage appear at the secondary coils of the

transformer(T901).

5)These secondary voltage are rectified by each diode (D941,D951,D961,D962,D9710 and operate other circuit.(horizontal and vertical deflection,video amplifer,...etc.)

4. X-ray Protection Circuit

When the high voltage reaches to 29kV in an abnormal case, tIC401(MICOM) pin 35 sensing from FBT directly. Then MICOM control IC701 (Deflection controller)to stophorizontal drive pulse and stop horizontal deflection.

5. Microprocessor Control Circuit

The operating procedure of MICOM(Microprocessor) and its associating circuit is as fallow:is as follows :

1) Horizontal and Vertical sync signals are supplied from the signabl cable.

2)Microprocessor(IC401) discriminates the operating mode from the sync polarity and resolution.

3) The Micom sets operating mode and offers the controlled data.(H-Size,H-Position,V-Size,...)

4) The controlled data of each mode is stored in itself.

5)User can adjust screen condition by each OSD

functio.tHhe data of the adjusted condition is stored in EEPROM(IC402).

6. Horizontal and Vertical Oscillation

This circuit generates the horizontal pulse and the

vertical pulse by takijg the H and V sync signal. This circuit consists pof the TDA4841(IC701) and the associate circuit.

7. D/D(DC to DC) Converter

This circuit supplies DC voltage to the horizontal deflection output circuit by increasing DC 50V which is the secdonary voltage of the SMPS in accordance with the input horizontal sync signal.

8. Side-Pincushion & Trapezoid Correction Circuit

This circuit improve the side-pincushion and the trapezoid distortion of the screen by mixing parabola and saw-tooth wave to output of the horizontal deflection D/D converter which is used for the supply voltage (B+) of the deflection circuit.

9. Horizontal Deflection Output Circuit

This circuit makes the horizontal deflection by supplying the saw-tooth current to the horizontal deflection yoke.

10. High Voltage Output & FBT(Flyback Transformer)

The high voltage output circuit is used for generating pulse to the primry coil of the FBT(Flyback Transformer )secondary of the FBT and it is supplied to the anode,focus,and screen voltage of the CRT.

11. H-Linearity Correction Circuit

This circuit corrects the horizontal linearity for each horizontal sync frequency.

12. Vertical Output Circuit

This circuit takes the vertical ramp wave from the TDA4841(IC701) and performs the vertical deflection by supplying the saw-tooth current to the vertical deflection yoke.

13. Dynamic Focus Output Circuit

This circuit takes the horizontal and the vertical parabola waves from the TDA4841(IC7010 and amplifies it to maintain constant focus on center and corners in the screen.

14. H & V Blanking and Brightness Control

Blanking circuit eliminate retrace line by supplying negatinve pulse to the G1 of the CRT.And Brightness circuit is used for control of the screen brightness by changeing DC level of the G1.

- 10 -

15.Image Rotation(Tilt)Circuit

This circuit corrects the tilts of the screen by supplying the image rotation signal to the tilt which is attached near the deflection yoke of the CRT.

16. Video Pre-AMP Circuit

This circuit amplifies the analog vdeo signal from 0-0.7V to 0-4V. It is operated by taking the clamp,R,G,B drive and contrast signal from the MICOM(IC401).

17.Video Output AMP Circuit

This circuit amplifies the video signal which comes from

tehe video pre-amp circuit and amplifies it to applied the CRT cathode.

- 11 -

ADJUSTMENT

GENERAL INFORMATION

All adjustment are thoroughly checked and corrected when the monitor leaves the factory, but sometimes several adjustments may be required. Adjustment should be following procedure and after warming up for a minimum of 30 minutes.

• Alignment appliances and tools.

- IBM compatible PC.

- Programmable Signal Generator. (eg. VG-819 made by Astrodesign Co.)

- EPROM or EEPROM with saved each mode data.

- Alignment Adaptor and Software.

- Digital Voltmeter.

- White Balance Meter.

- Luminance Meter.

- High-voltage Meter.

AUTOMATIC AND MANUAL DEGAUSSING

The degaussing coil is mounted around the CDT so that automatic degaussing when turn on the monitor. But a monitor is moved or faced in a different direction, become poor color purity cause of CDT magnetized, then

press

DEGAUSS on the OSD menu.

ADJUSTMENT PROCEDURE & METHOD

-Install the cable for adjustment such as Figure 1and run

the alignment program on the DOS for IBM compatible PC.

-Set external Brightness and Contrast volume to max position.

1. Adjustment for High-Voltage.

1) Display cross hatch pattern at MOde 4.

2) DIST.ADJ→CTRL PWM →High Voltage Command.

3) Adjust High Voltage to 25.8kV

0.1kVdc.

3) Press Enter Key.

2. Adjustment for Factory Mode (Preset Mode).

1) Display cross hatch pattern at Mode 1.

2) Run alignment program for FB774G on the IBM compatible PC.

3) EEPROM →ALL CLEARÆY(YES) command.

<Caution> Do not run this procedure unless the

EEPROM is changed.All data in EEPROM

(mode data and color data) will be erased.

4) Power button of the monitor turn off→turn on.

5) COMMAND → START Æ Y(Yes) command.

6) DIST. ADJ. → CTRL PWMÆTILT command.

7) Adjust tilt as arrow keys to be the best condition.

DIST. ADJ. → BALANCE command.

Adjust parallelogram as arrow keys to be the best

condition.

10)

Adjust balance of pin-balance as arrow keys to be

the best condition.

11)

DIST.ADJ Æ FOS.ADJ command.

12)

Adjust V-SIZE as arrow keys to 200±4mm.

13)

Adjust V-POSITION as arrow keys to center of the screen.

14)

Adjust H-SIZE as arrow keys to 270±4mm.

15)

Adjust H-POSITION as arrow keys to center of the screen.

16)

Adjust S-PCC (Side-Pincushion) as arrow keys to be the best condition.

17)

Adjust TRAPEZOID as arrow keys to be the best condition.

18) Save of the Mode 1.

19)

Display from Mode 2 to Mode 4 and repeat above from number

12)

19)

18)

PRESET EXIT → Y (Yes) command.

3. Adjustment for White Balance and Luminance.

1) Set the White Balance Meter.

Press the DEGAUSS on the OSD menu for demagnetization of the CDT.

3) COLOR ADJ. → LUMINANCE command of the alignment program.

4) Set Brightness and Contrast to Max position.

5) Display color 0,0 pattern at Mode 4.

6) COLOR ADJ. → BIAS ADJ.→COLOR No.→1 command of the alignment program.

7) Check whether green color or not at R-BIAS and G-BIAS to min position and B-BIAS to 127(7F) position.Set Sub-Brightness to 177(B1) position.Adjust G2(Screen) command to 0.4

±0.05FL

of the raster luminance.

8) Adjust R-BIAS and G-BIAS command to x=0.283

0.005 and y=0.298±0.005 on the White Balance Meter with PC arrow keys.

9) Adjust SUB-Brightness command to 0.4

0.1FL of the

raster luminance.

10)

Adjust repeat number 8).

11)

After push the ENTER key.

11-1

)

COMMAND→PRESET START→Y(Yes) command.

) Display color 15,0 full white pattern at Mode 4.

13)

DRIVE ADJ.→No 1. command.

14)

Set Brightness and Contrast to Max position.

15)

Set SUB-CONTRAST Max 127(7F)(decimal) position.

16)

Set B-DRIVE to 100(64) at DRIVE of the alignment

program.

17-1)

Adjust R-DRIVE and G-DRIVE command to white

balance x=0.283

0.003 and y=0.298±0.003 on the

- 12 -

White Balance Meter with PC arrow keys.

17-2)

Display color 15,0 window pattern (70x70mm) at

mode 4.

18)

Adjust SUB-CONTRAST command to 50±1FL .

19)

Display color 15,0 full white patten at Mode 4.

20)

Set Brightness and Contrast to Max position.

21)

COLOR ADJ. → LUMINANCE → ABL command.

22)

Adjust ABL to 32±1FL of the luminance.

23)

After push the ENTER key,and COMMAND→ PRESET EXIT

→Y(Yes) command.

24)

Exit the program.

4. Input EDID Data.

1) Display color 15,0 cross hatch pattern at Mode 4.

2) EEPROM

Write EDID command and confirm

"EDID Write OK "message of monitor.

3) Exit from the alignment program.

4) Power switch OFF/ON for EDID data save.

5.Adjustment for Focus.

1) Set the Brighteness and Contrast to max position.

2) Display H character in full screen at MOde 4.

3) Adjust two Focus contro on the FBT that focus should be the best condition.

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