LG T730SH Schematic

COLOR MONITOR

SERVICE 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.

MODEL:

T730SH

(T730SHMKQ-K***V*)

CHASSIS NO. : CM54A

( ) **Same model for Service

*Same looking with new chassis.

CONTENTS

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

SAFETY PRECAUTIONS ........................................

SERVICE PRECAUTION.......................................... 4

TIMING CHART ....................................................... 7

WIRING DIAGRAM ................................................. 9

DISASSEMBLY ....................................................... 8

BLOCK DIAGRAM ...................................................

SPECIFICATIONS

1. PICTURE TUBE Size : 17 inch DefIection Angle : 90¡ Neck Diameter : 29.1 mm Stripe Pitch : 0.25 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 

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 ~ 71 kHz Vertical : 50 ~ 160 Hz

3. POWER SUPPLY 3-1. Power Range

AC 100-240V~ 50/ 60Hz, 1.0A

DESCRIPTION OF BLOCK DIAGRAM................... 11

ADJUSTMENT ....................................................... 13

TROUBLESHOOTING GUIDE .............................. 19

EXPLODED VIEW...................................................35

SCHEMATIC DIAGRAM ......................................... 37

PRINTED CIRCUIT BOARD................................... 39

3-2. Power Consumption

MODE

NORMAL (ON)

DPMS OFF

POWER OFF

VIDEO

YES

4. DISPLAY AREA 4-1. Active Video Area :

Max Image Size - 325.1 x 243.8 mm (12.80" x 9.60")

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)

4-4. Video Bandwidth : 110 MHz

5. ENVIRONMENT 5-1. Operating Temperature: 0¡C ~ 40¡C

5-2. Relative Humidity : 10%~ 80%

5-3. Altitude : 5,000 m

6. DIMENSIONS (with TILT/SWIVEL) Width : 400 mm (15.75 inch) Depth : 411 mm (16.18 inch) Height : 401 mm (15.79 inch)

7. WEIGHT (with TILT/SWIVEL)

Net Weight : 13.3 kg Gross Weight : 16.2 kg

POWER CONSUMPTION

less than 63 W

less than 3 W less than 3 W

(Non-Interlace)

(Ambient)

(Non-condensing)

LED COLOR

BLUE

FLICKER

OFF

- 2 -

SAFETY PRECAUTIONS

- 3 -

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 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.

Leakage Current Hot Check Circuit

CAUTION:

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

1.5 Kohm/10W

To Instrument's exposed METALLIC PARTS

Good Earth Ground such as WATER PIPE, CONDUIT etc.

AC Volt-meter

- 4 -

SERVICING PRECAUTIONS

CAUTION: Before servicing receivers covered by this

service manual and its supplements and addenda, read and follow the SAFETY PRECAUTIONS on page 3 of this publication. NOTE: If unforeseen circumstances create conflict between the following servicing precautions and any of the safety precautions on page 3 of this publication, always follow the safety precautions. Remember: Safety First.

General Servicing Precautions

1. Always unplug the receiver AC power cord from the AC power source before; a. Removing or reinstalling any component, circuit

board module or any other receiver assembly.

b. Disconnecting or reconnecting any receiver electrical

plug or other electrical connection.

c. Connecting a test substitute in parallel with an

electrolytic capacitor in the receiver. CAUTION: A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result in an 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 kine aquadag grounding system shield at the point where the picture tube socket ground lead is connected, and then (b) touch 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 spray chemicals on or near this receiver or any of its assemblies.

5. Unless specified otherwise in this service manual, clean electrical contacts only by applying the following mixture to the contacts with a pipe cleaner, cottontipped stick or comparable non-abrasive applicator; 10% (by volume) Acetone 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 in not required.

6. Do not defeat any plug/socket B+ voltage interlocks with which receivers 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 receiver ground lead to the receiver chassis ground before connecting the test receiver positive lead. Always remove the test receiver ground lead last.

9. Use with this receiver only the test fixtures specified in

this service manual.

CAUTION: Do not connect the test fixture ground strap to any heat sink in this receiver.

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. Examples of typical ES devices are integrated circuits and 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 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 to prevent 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 "antistatic" can generate electrical charges sufficient to damage ES devices.

5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient 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 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 harmless motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity sufficient to damage an ES device.)

- 5 -

General Soldering Guidelines

1. Use a grounded-tip, low-wattage soldering iron and appropriate tip size and shape that will maintain tip

temperature within the range or 500

F to 600 F.

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 and well tinned.

4. Thoroughly clean the surfaces to be soldered. Use a mall 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 unsoldering technique a. Allow the soldering iron tip to reach normal

temperature. (500

F to 600 F) b. Heat the component lead until the solder melts. c. Quickly draw the melted solder with an anti-static,

suction-type solder removal device or with solder braid. CAUTION: Work quickly to avoid overheating the circuitboard printed foil.

6. Use the following soldering technique. a. Allow the soldering iron tip to reach a normal

temperature (500

F to 600 F)

b. First, hold the soldering iron tip and solder the 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. CAUTION: Work quickly to avoid overheating the circuit board printed foil.

d. Closely inspect the solder area and remove any

excess or splashed solder with a small wire-bristle brush.

IC Remove/Replacement

Some chassis circuit boards have slotted holes (oblong) through which the IC leads are inserted and then bent flat against the circuit foil. When holes are the slotted type, 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 and 6 above.

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 solder 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 areas).

"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 into a "U" shape the end of each of three leads remaining on the circuit board.

3. Bend into a "U" shape the replacement transistor leads.

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 Output, Transistor Device Removal/Replacement

1. Heat and remove all solder from around the transistor leads.

2. Remove the heat sink mounting screw (if so equipped).

3. Carefully remove the transistor from the heat sink of the circuit board.

4. Insert new transistor in the circuit board.

5. Solder each transistor lead, and clip off excess lead.

6. Replace heat sink.

Diode Removal/Replacement

1. Remove defective diode by clipping its leads as close as possible to diode body.

2. Bend the two remaining leads perpendicular y to the circuit board.

3. Observing diode polarity, wrap each lead of the new diode around the corresponding lead on the circuit board.

4. Securely crimp each connection and solder it.

5. Inspect (on the circuit board copper side) the solder joints of the two "original" leads. If they are not shiny, reheat them and if necessary, apply additional solder.

Fuse and Conventional Resistor Removal/Replacement

1. Clip each fuse or resistor lead at top of the circuit board hollow stake.

2. Securely crimp the leads of replacement component around notch at stake top.

3. Solder the connections. CAUTION: Maintain original spacing between the replaced component and adjacent components and the circuit board to prevent excessive component temperatures.

- 6 -

Circuit Board Foil Repair

Excessive heat applied to the copper foil of any printed circuit board will weaken the adhesive that bonds the foil to the circuit board causing the foil to separate from or "lift-off" the board. The following guidelines and procedures should be followed whenever this condition is encountered.

At IC Connections

To repair a defective copper pattern at IC connections use the following procedure to install a jumper wire on the copper pattern side of the circuit board. (Use this technique only on IC connections).

1. Carefully remove the damaged copper pattern with a sharp knife. (Remove only as much copper as absolutely necessary).

2. carefully scratch away the solder resist and acrylic coating (if used) from the end of the remaining copper pattern.

3. Bend a small "U" in one end of a small gauge jumper wire and carefully crimp it around the IC pin. Solder the IC connection.

4. Route the jumper wire along the path of the out-away copper pattern and let it overlap the previously scraped end of the good copper pattern. Solder the overlapped area and clip off any excess jumper wire.

At Other Connections

Use the following technique to repair the defective copper pattern at connections other than IC Pins. This technique involves the installation of a jumper wire on the component side of the circuit board.

1. Remove the defective copper pattern with a sharp knife. Remove at least 1/4 inch of copper, to ensure that a hazardous condition will not exist if the jumper wire opens.

2. Trace along the copper pattern from both sides of the pattern break and locate the nearest component that is directly connected to the affected copper pattern.

3. Connect insulated 20-gauge jumper wire from the lead of the nearest component on one side of the pattern break to the lead of the nearest component on the other side. Carefully crimp and solder the connections. CAUTION: Be sure the insulated jumper wire is dressed so the it does not touch components or sharp edges.

- 7 -

TIMING CHART

* No Composite Mode.

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

Video

Sync

MODE

1 2 3 4

Polarity

- + + +

H H-Frequency KHz

37.500 46.880 53.680 68.677

O H-Active (A) uS

26.670 21.330 18.630 14.561

R H-Video(B) uS

20.320 16.160 14.220 10.836

I H-blanking(C) uS

6.350 5.170 4.410 3.725

Z H-front porch(D) uS

0.510 0.320 0.570 0.508

H-sync time(E) uS

2.030 1.620 1.140 1.016

H-back porch(F) us

3.810 3.223 2.700 2.201

Polarity

- + + +

V-Frequency Hz

74.990 75.010 85.070 85.000

V-Active (A) mS

13.335 13.331 11.755 11.764

V V -Video(B) mS

12.802 12.798 11.178 11.182

E V-blanking(C) mS

0.533 0.533 0.577 0.582

R V-front porch(D) mS

0.026 0.021 0.018 0.014

T V-sync time(E) mS

0.080 0.064 0.056 0.044

V-back porch(F) mS

0.427 0.448 0.503 0.524

Resolution

640* 800* 800* 1024*

480 600 600 768

VESA

- 8 -

DIS A S S E MB LY

1. T IL T /S WIV E L & B A C K C OV ER R E MOV AL

1) S et the monitor fac e downward.

2) C arefully remove the T ilt/S wivel by pulling it upward.

3) Remove the screw (b), Back cover by pushing it upward.

4) R eleas e the latch (c). (S ee T ip S pec.)

5) S lide the B ack C over a wa y from the F ront C abinet of the monitor.

Tip S pec . A(W idth) : 5.0~15. 0mm B (Depth) : 0.6~0.9mm C (Height) : 12.0mm

B a

C ov e

(c )

C abin et

(b)

(a )

T ip

WIRING DIAGRAM

- 9 -

P501

P201

P405

P301

P302

P702

P701

P402

P902

Signal Cable

AC Socket

FBT

P220

P203

P202

P904

BLOCK DIAGRAM

- 1 0 -

Dynamic Focus

Static Focus

H.V

DY CDT

Screen

Heater ( 6.3V )

VIDEO

8V 80V

G/B

(IC303)

Main AM P

15V

- 160V

Brightness Control

FBT

( T701 )

40V

15V

Auto

Beam

LimitDC/DC Converter

D/D

Feed Back

Circuit

FOCUS

Dynamic

B+

Circuit

Regulation

X-R AY

Circuit

Protection

OSD

VIDEO

Video

H-Sync

Pre- AMP /

RGB

Signal

V-Sync

(IC302)

SCL / SDA

H-Sync/V-Sync

PWM Control Signal

( IC 401 )

C CLOCK(SCL)

C DATA(SD A)

SAA4849

MICOM & H/V Sync Processor

V-Out

( IC 601)

15V

PROM

(IC402)

6.3V

H-Out

TDA4867J

( Q706)

15V

H-Linearity

Correction

50V

H - Drive

B-Drive

DPM

Control

Circuit

15V

50V

80V

SMPS

(T901)

V 15

6.3V

Voltage

feedback

SMPS

Control

(IC901)

BRIGHTNESS

TILT

Control

Circuit

MOIRE

CONTRAST

SPCC

H / V SI ZE

TRAPEZOID

DEG AUSSING

H / V POSI TION

PIN BAL ANC E

COLOR

OSD TIME

LANGU AGE

VIDEO LEVEL

INFORMATION

ROTATION (Tilt)

RECALL / RESET

PAR ALL ELOGR AM

TOP/BOTTOM CORNER

OSD CONTROL LOCK

[ OSD Control ]

TILT

Coil

Degaussing

Line

Filter

(50/60Hz)

Power Input

100~240V AC

Degaussing

Coil

DESCRIPTION OF BLOCK DIAGRAM

- 11 -

1. SMPS(Switching Mode Power Supply) When you turn on the power switch, the operating fprocedure is as follows:

6. X-RAY Protection Circuit When the high Voltage reaches to 29kV in an abnormal case, the high voltage detector circuit, R818,D721,C739-1 R416, C409 start operation to shut down high voltage circuit.

7. Horizontal S-correction Circuit. This circuit corrects the horizontal linearity for each horizontal sync frequency.

8. Horizontal drive and Output Circuit. This circuit is a horizontal deflection amplifier for raster scan.

9. ABL Circuit This circuit limits the beam-current for the reliability of CDT

10. Vertical Output Circuit This circuit takes the vertical ramp wave from the TDA4867J (IC601) and perform the vertical deflection by supplying the saw-tooth wave current to the vertical deflection yoke.

11. Blanking and Brightness Control Circuit. Blanking circuit eliminates the retrace line by supplying a negative pulse wave to the G1 of the CDT. Brightness control circuit is used for control of the screen brightness by changing the DC level G1.

12. 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 CDT.

13. OSD (On Screen Display) Circuit. This circuit displays information of the monitor`s status on the screen.

14. Video Processor Circuit. Video processor circuit consists of the video drive output block. The video drive IC(IC302) receives the video signal from PC. The gain of each channel is controlled by MICOM through IIC. The cut-off circuit compensate different voltage of each channel between the cathode and the G1 of the CDT.

1) The AC line voltage is rectified by the bridge diode D900.

2) The control IC(IC901) starts switching and generates

switch pulse in the primary turn of the SMPS transformer(T901)

3) The switching pulses of the primary turns are induced

to the secondary turns of the transformer by the turn ratio. This pulses are rectified by each diode(D971,

D961(D962),D951,D942,D941)

4) Each rectified DC voltage(80V, 50V, 15V,6.3V and 5V)

2. Over Voltage Protection Circuit When the input of IC901 Vin (pin 4) is more than 22V, all the secondary voltages of the SMPS transformer (T901) down to low value

3. Display Power Management Circuit(DPM)

1) DPM OFF When no input of horizontal or vertical sync Q951, Q941 are turned off .Then input power consumption is below 4 watts.

4. Microprocessor Control & Horizontal and Vertical Sync

Processor Circuit

The operating procedure is as follows ;

1) There is Horizontal & Vertical process function in

Microprocessor.(IC401)

2) Microprocessor (IC401) discriminates the operating mode

from the sync polarity and resolution.

3) After microprocessor reads these adjusted mode data stored at EEPROM, it controls operating mode data through

IIC

4) Users can control screen condition by the OSD Select,Up, Down, Left, Right, Exit.

5. D/D Converter Circuit.

To obtain constant high voltage, this circuit supplies

controlled DC voltage for FBT and horizontal deflection

circuit according to the horizontal sync frequency.

- 12 -

15. Video Pre-Amp Circuit. This circuit amplifies the analog video signal from 0~0.7 V to 0~4 V. It is operated by taking the clamp, R,G,B drive and contrast signal from the MICOM (IC401)

16. Video Output Amp Circuit. This circuit amplifies the video signal which comes from the video pre-amp circuit and amplified it to applied the CDT cathode

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