LG FB775H Service Manual

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COLOR MONITOR

SERVICE MANUAL

CHASSIS NO. : CA-124

FACTORY MODEL: FB775H

MODEL: F775FT(FB775H-EL)

*( ) ID LABEL Model No.

CAUTION

BEFORE SERVICING THE UNIT,

READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CONTENTS

SPECIFICATIONS ...................................................	2
SAFETY PRECAUTIONS ........................................	3
TIMING CHART .......................................................	4
OPERATING INSTRUCTIONS ................................	5
CONTROL LOCATION ............................................	6
WIRING DIAGRAM .................................................	7
BLOCK DIAGRAM ...................................................	8

DESCRIPTION OF BLOCK DIAGRAM...................	. 9
ADJUSTMENT .......................................................	11
TROUBLESHOOTING GUIDE ..............................	13
EXPLODED VIEW...................................................	23
REPLACEMENT PARTS LIST ...............................	25
PIN CONFIGURATION...........................................	31
SCHEMATIC DIAGRAM.........................................	36

SPECIFICATIONS

1. PICTURE TUBE
Size	: 17 inch
DefIection Angle	: 90°
Neck Diameter	: 29.1 mm
Stripe Pitch	: 0.24 mm
Face Treatment	: W-ARASC (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	: 75 Ω
	3)	Video Color	: R, G, B Analog
	4)	Signal Format	: Refer to the Timing Chart
2-3.	Signal Connector
	3 row 15-pin Connector (Attached)
2-4.	Scanning Frequency
	Horizontal		: 30 ~ 70 kHz
	Vertical		: 50 ~ 160 Hz

3.POWER SUPPLY

3-1. Power Range

AC 110~220V (Free Voltage), 60Hz, 2.0A Max.

3-2. Power Consumption

	MODE	POWER CONSUMPTION		LED COLOR
	NORMAL (ON)	73 W		GREEN
	STAND-BY	less than 15	W	AMBER
	SUSPEND	less than 15	W
	OFF	less than 5	W	AMBER

4. DISPLAY AREA

4-1. Active Video Area :

•Max Image Size - 325.4 x 244.1 mm (12.81" 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(Max)
		(Non-Interlace)
4-4.	Video Bandwidth	: 110 MHz

5.ENVIRONMENT

5-1. Operating Temperature: 0°C ~ 40°C

		(Ambient)
5-2. Relative Humidity		: 10%~ 90%
		(Non-condensing)
5-3. Altitude		: 5,000 m
6. DIMENSIONS (with TILT/SWIVEL)
Width	: 415.0 mm (16.34 inch)
Depth	: 439.0 mm (17.28 inch)
Height	: 435.0 mm (17.13 inch)
7. WEIGHT (with TILT/SWIVEL)
Net Weight	: 17.8 kg (39.24 lbs.)
Gross Weight	: 21.0 kg (46.30 lbs.)

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SAFETY PRECAUTIONS

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 manufacturer 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 25.8kV. The following steps describe how to measure the high voltage and how to prevent X- radiation.

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.

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TIMING CHART

VIDEO

C B

SYNC

D E F

A

<< Dot Clock (MHz), Horizontal Frequency (kHz), Vertical Frequency (Hz), Horizontal etc... (µs) , Vertical etc... (ms) >>

	Mode	H/V	Sync	Frequency	Total Period	Video Active	Blanking Time	Sync Duration	Back Porch	Front Porch	Resolution
		Sort	Polarity		(A)	Time (B)	(C)	(E)	(F)	(D)
	1	H	–	37.50	26.67	20.32	6.35	2.03	3.81	0.51	640x480
		V	–	74.99	13.335	12.802	0.533	0.080	0.427	0.026	75Hz
	2	H	+	46.88	21.33	16.16	5.17	1.62	3.23	0.32	800x600
		V	+	75.01	13.331	12.798	0.533	0.064	0.448	0.021	75Hz
	3	H	+	53.68	18.63	14.22	4.41	1.14	2.70	0.57	800x600
		V	+	85.07	11.755	11.178	0.577	0.056	0.503	0.018	85Hz
	4	H	+	68.677	14.561	10.836	3.725	1.016	2.201	0.508	1024x768
		V	+	85.00	11.764	11.182	0.582	0.044	0.524	0.014	85Hz

* Mode 1~Mode 4: Basic Mode

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OPERATING INSTRUCTIONS

	FRONT VIEW			REAR VIEW
	Power Button	AC Power Socket
	See Front Control Panel				Signal Cable
	Front Control Panel
	OSD		SET
	5	4	3	2	1
1.	Power ON/OFF Button	3.	SET Button

This button is used to turn the monitor ON and OFF.

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

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.

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.

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CONTROL LOCATIONS

VR901: B+ Adjustment

(50V Line)

- 6 -

WIRING DIAGRAM

	Anode Cap
	DY-Pin
	Degaussibg Coil
	P801	P902
		P702
	P201-
	(Control PCB)	P502
	P405
		P501
	P402
	- 7 -

OSD CONTROL

105V

H.V

Heater ( 6.3V )

Signal

BRIGHTNESS

H-Sync Sig

R

Cable

VIDEO

CONTRAST

VIDEO

V-Sync Sig

G

H/V POSITION

PRE-AMP

DY

CDT

H/V SIZE

I2C DATA(SDA)

B

MAIN AMP

(IC302)

(IC303)

SPCC

I2C CLOCK(SCL)

STV9211

TRAPEZOID

STV9556

1G

PIN BALANCE

13VScreen(G2)

PARALLELOGRAM

MICOM

OSD IC

5V

13V

ROTATION

5V

RECALL

5V

(IC401)

SCL / SDA

(IC301)

I2C

Focus Static

FocusDynamic

DEGAUSS

H/V Sync,

WT6805

R/G/B

OSD TIME

PWM Control

I2C

Drive/Contrast

COLOR CURVE

MOIRE

Cut-Off

LANGUAGE

RESET

VIDEO LEVEL

X-RAY

DIAGRAM BLOCK

E2PROM

I2C

12V

Protection

Vertical Blanking,

6.3V

(IC402)

Circuit

Brightness Control

DEGAUSSING TILT Purity

Purity

13V

-10V

13V

Control

H/V Sync Processor

- 160V

Circuit

6.3V

( IC701 )

Vout 1

TILT

13V

Vout 2

V-OUT

I2C

STV6888

40V

( IC601)

Control

Circuit

H/V

STV9302

Degaussing

Sync

FBT

Circuit

13V

105V

( T701 )

8--

COILCOILCOIL

50V

H-OUT

SMPS

13V

H-DRV

( Q706)

B+

13V

TRANS

Line

(T901)

6.3V

400V

H-Linearity

Filter

Correction

Dynamic

Auto

5V

Focus

Beam

SMPS

DPM

Voltage

DC/DC Converter

Circuit

Limit

STEP UP

CONTROL

-10V

Regulating

B-DRV

CONTROL

Circuit

50V

POWER INPUT

(IC901)

CIRCUIT

100~240VAC

(50/60Hz)

D/D Feed Back

DESCRIPTION OF BLOCK DIAGRAM

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 this monitor flowing out through the power input line.

That is to say, this circuit prevents interference between the monitor and other electric appliances.

2. Degauss Circuit & Coil.

The degauss circuit consists of the degaussing coil, the PTC(Positive Temperature Coefficient) thermistor(TH901), and the relay(RL901). This circuit eliminates abnormal color of the screen automatically by degaussing the shadow mask in the CRT during turning on the power switch. When you need to degauss 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 procedure is as follows:

1) AC input voltage is rectified and smoothed by the bridge diodes (D900) and the capacitor (C908).

2) The rectified voltage(DC) is applied to the primary coil of the transformer(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 ratio of the transformer, the secondary voltages appear at the secondary coils of the transformer(T901).

5) These secondary voltages are rectified by each diode(D941, D942, D951, D961, D971) and operate other circuit. (horizontal and vertical deflection, video amplifier,

...etc.)

4.X-ray Protection.

If the high voltage of the FBT reaches up to 29kV (abnormal state), IC401(MICOM) pin 35 Sensing from FBT directly. Then MICOM control IC701 (Deflection controller) to stop Horizontal drive pulse and stop Horizontal Deflection.

5. Micom(Microprocessor) Circuit.

The operating procedure of Micom(Microprocessor) and its associated circuit is as follows:

1)H and V sync signal is supplied from the signal cable.

2)The Micom(IC401) distinguishes polarity and frequency of H and V sync.

3)The Micom sets operating mode and offers the controlled data. (H-size, H-position, V-size, ... etc.)

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

5)User can adjust screen condition by each OSD function. The 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 taking the H and V sync signal.

This circuit consists of the STV9302(IC601) and the associated 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 secondary voltage of the SMPS in accordance with the input horizontal sync signal.

8.Side-Pincushion & Trapezoid Correction Cirucit.

This circuit improves 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 primary 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 STV6888(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 STV6888(IC701) and amplifies it to maintain constant focus on center and corners in the screen.

14. H & V Blanking and Brightness Control.

Blanking circuit eliminates retrace line by supplying negative pulse to the G1 of the CRT. And Brightness circuit is used for control of the screen brightness by changing DC level of the G1.

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15. Image Rotation (Tilt) Circuit.

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

16. Video Pre-Amp Circuit.

This circuit amplifies the analog video 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 the video pre-amp circuit and amplified it to applied the CRT cathode.

- 10 -

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±0.1 kVdc.

4)Press Enter Key.

2.Adjustment for Factory Mode (Preset Mode).

1)Display cross hatch pattern at Mode 1.

2)Run alignment program for FB775H on the IBM compatible PC.

3)	EEPROM →	ALL CLEAR → Y(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→	PRESET START→ Y(Yes) command.
6)	DIST. ADJ. →	CTRL PWM → TILT command.

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

8)DIST. ADJ. → BALANCE command.

9)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. → FOS. ADJ command.

12)Adjust V-SIZE as arrow keys to 230±2mm.

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

14)Adjust H-SIZE as arrow keys to 310±2mm.

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 4 and repeat above from number 12) to 19)

20)PRESET EXIT → Y (Yes) command.

3.Adjustment for White Balance and Luminance.

1)Set the White Balance Meter.

2)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 250(CD) and Sub-Brightness to 127(2F) 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.

12)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 220(CD) (decimal) position.

16)Set B-DRIVE to 150(96) at DRIVE of the alignment program.

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