LG Flatron L1742P, Flatron L1942P Service Manual

COLOR MONITOR

SERVICE MANUAL

CAUTION

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

CHASSIS NO. : LM72A

MODEL:

L1742P (L1742P-*FT.A***QPN)

*To apply the MSTAR Chip .

( ) **Same model for Service

Website:http://biz.LGservice.com

Internal Use Only

L1942P(L1942P-*FT.A***QPN)

AUTO/SET VOLUME

- 2 -

LGE Internal Use Only

CONTENTS

1. LCD CHARACTERISTICS

Type : TFT Color LCD Module Active Display Area : 17 inch - L1742P

: 19 inch - L1942P

Pixel Pitch : 0.264 (H) x 0.264 (V) - L1742P

: 0.294 (H) x 0.294 (V) - L1942P Color Depth : 8bits, 16.7M colors Size :

358.5 (H) x 296.5 (V) x 16.0(D) - L1742P

396 (H) x 324 (V) x 15.5(D) - L1942P Electrical Interface : LVDS Surface Treatment : Hard-coating(3H), Anti-Glare Operating Mode :

Normally White, Transmissive mode Backlight Unit : 4-CCFL

2. OPTICAL CHARACTERISTICS

2-1. Viewing Angle by Contrast Ratio ≥ 10

Left : -60° min., -70°(Typ) Right : +60° min., +70°(Typ) Top :+60° min., +75°(Typ) Bottom : -50° min., -65°(Typ)

2-2. Luminance :

230(min), 300(Typ) (Full White pattern, 0.70V) -6500K

150(min) (Full White pattern, 0.70V) -9300K

75%(min) 2-3. Contrast Ratio : 8000:1 (DFC)

3. SIGNAL (Refer to the Timing Chart)

3-1. Sync Signal

• Type : Separate Sync, Digital, SOG

3-2. Video Input Signal

1) Type : R, G, B Analog

2) Voltage Level : 0~0.71 V a) Color 0, 0 : 0 Vp-p b) Color 7, 0 : 0.467Vp-p c) Color 15, 0 : 0.714Vp-p

3) Input Impedance : 75Ω

3-3. Operating Frequency

Horizontal : 30 ~ 83kHz Vertical : 56 ~ 75Hz

4. Max. Resolution

D-sub Analog : 1280 x 1024@75Hz Digital : 1280 x 1024@60Hz

5. POWER SUPPLY

5-1. Power : AC 100~240V, 50/60Hz , 0.6A 5-2. Power Consumption

6. ENVIRONMENT

6-1. Operating Temperature : 10°C~35°C (50°F~95°F)

(Ambient) 6-2. Relative Humidity : 10%~80% (Non-condensing) 6-3. MTBF : 50,000 HRS with 90% Confidence

Lamp Life : 50,000 Hours(Min)

7. DIMENSIONS (with TILT/SWIVEL) L1742P

Width : 369.6 mm (14.55'') Depth : 241.6 mm (9.51'') Height : 408.3 mm(16.07'')~518.3 mm (20.41'')

L1942P

Width : 406.3 mm (16.00'') Depth : 241.6 mm (9.51'') Height : 422.7 mm (16.64'')~532.7 mm(20.97'')

8. WEIGHT (with TILT/SWIVEL) L1742P

Net. Weight : 3.83 kg ( 8.51 lbs) Gross Weight : 5.37 kg (11.93lbs)

L1942P

Net. Weight : 4.23 kg (9.40 lbs) Gross Weight : 5.94 kg (13.20lbs)

SPECIFICATIONS

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

PRECAUTIONS ....................................................... 3

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

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

BLOCK DIAGRAM...................................................12

DISCRIPTION OF BLOCK DIAGRAM .................. 14

ADJUSTMENT ...................................................... 16

SERVICE OSD........................................................17

TROUBLESHOOTING GUIDE .............................. 18

WIRING DIAGRAM ............................................... 24

EXPLODED VIEW...................................................25

REPLACEMENT PARTS LIST ...............................27

SCHEMATIC DIAGRAM......................................... 32

MODE

POWER ON (NORMAL)

STAND-BY

SUSPEND

DPMS OFF

POWER S/W Off

H/V SYNC

ON/ON

OFF/ON ON/OFF OFF/OFF

POWER CONSUMPTION

less than 30 W -L1742P less than 34 W -L1942P

less than 1 W less than 1 W less than 1 W less than 1 W

LED COLOR

BLUE

or Flicker

Flicker Flicker Flicker

OFF

VIDEO

ACTIVE

OFF OFF OFF

- 3 -

PRECAUTION

LGE Internal Use Only

WARNING FOR THE SAFETY-RELATED COMPONENT.

• There are some special components used in LCD monitor that 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 electric shock, fire or other hazard.

• Do not modify original design without obtaining written permission from manufacturer or you will void the original parts and labor guarantee.

TAKE CARE DURING HANDLING THE LCD MODULE WITH BACKLIGHT UNIT.

• Must mount the module using mounting holes arranged in four corners.

• Do not press on the panel, edge of the frame strongly or electric shock as this will result in damage to the screen.

• Do not scratch or press on the panel with any sharp objects, such as pencil or pen as this may result in damage to the panel.

• Protect the module from the ESD as it may damage the electronic circuit (C-MOS).

• Make certain that treatment person’s body are grounded through wrist band.

• Do not leave the module in high temperature and in areas of high humidity for a long time.

• The module not be exposed to the direct sunlight.

• Avoid contact with water as it may a short circuit within the module.

• If the surface of panel become dirty, please wipe it off with a softmaterial. (Cleaning with a dirty or rough cloth may damage the panel.)

WARNING

BE CAREFUL ELECTRIC SHOCK !

• If you want to replace with the new backlight (CCFL) or inverter circuit, must disconnect the AC adapter because high voltage appears at inverter circuit about 650Vrms.

• Handle with care wires or connectors of the inverter circuit. If the wires are pressed cause short and may burn or take fire.

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

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: I f unforeseen circums ta nces cre ate conf li ct between the following servicing precautions and any of the safety p

recautions 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 paralle l 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. Te st

hig h vo lta ge only b y mea sur ing it wi th an

appro pri

ate hi gh vol tage m eter or oth er vol tage

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 connecti

ng one end of an insulated clip lead to the

degaussi

ng or kine aquadag grounding system shield

at the point where the picture tube

socket ground lead

is connec

ted, and then (b) touch the other end of the

insulate

d 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, cotton-

tipped s

tick or comparable non-abrasive applicator;

10% (by

volume) Acetone and 90% ( by vol um e) 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 whi

ch receivers covered by this service manual

might be equipped.

7. Do not apply AC power

to this instrument and/or any of

its elec

trical assemblies unless all solid-state device

heat sinks are correctly installed.

8. Always

connect the test receiver ground lead to the

receive

r 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 sem

icond uct or ( solid -st ate ) de vices can be

damaged

easily by static electricity. Such components

commonly

are called Electrostatically Sensitive (ES)

Devices.

Examples of typical ES devices are integrated

cir cuits

and som e f ield- eff ect transis tor s a nd

sem icond

uct or "chip " comp one nts . T he fol lowin g

techniques should be used to

help reduce the incidence of

component damage caused by static by static electricity.

1. Immedi ately be fore han dling an y semico nductor component or semiconductor-equipped assembly, drain off

any electrostatic charge on your body by touching a

known ea

rth ground. Alternatively, obtain and wear a

commerci

ally available discharging wrist strap device,

which sh

ould 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 de vic

es , p lace the assembly on a conductiv e

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 onl

y an anti-static type solder removal device.

Some sol

der removal devices not classified as "anti-

static"

can generate electrical charges sufficient to

damage ES devices.

5. Do not

use freo n-pro pelled chemicals. These can

generate

electrical charges sufficient to damage ES

devices.

6. Do not

remove a replacement ES device from its

protecti

ve package until immediately before you are

ready to

install it. (Most replacement ES devices are

packaged

with leads electrically shorted together by

con ducti

ve fo am, al uminu m f oil or comp ara ble

conductive material).

7. Immedi

ately before removing the protective material

from the leads of a replacement

ES device, touch the

protecti

ve 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 replacem

ent ES devices. (Otherwise harmless motion

such as the brushing together of

your clothes fabric or

the lift

ing o f y our foot from a carpe ted floor can

generate

static electricity sufficient to damage an ES

device.)

- 4 -

LGE Internal Use Only

SERVICING PRECAUTIONS

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.

- 5 -

LGE Internal Use Only

- 6 -

LGE Internal Use Only

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.

TIMING CHART

VIDEO

SYNC

1 H(Pixels) + 25.175 31.469 800 640 16 96 48 640 x 350

V(Lines) - 70.09 449 350 37 2 60

2 H(Pixels) - 28.321 31.468 900 720 18 108 54 720 X 400

V(Lines) + 70.08 449 400 12 2 35

3 H(Pixels) - 25.175 31.469 800 640 16 96 48 640 x 480

V(Lines) - 59.94 525 480 10 2 33

4 H(Pixels) - 31.5 37.5 840 640 16 64 120 640 x 480

V(Lines) - 75 500 480 1 3 16

5 H(Pixels) + 40.0 37.879 1056 800 40 128 88 800 x 600

V(Lines) + 60.317 628 600 1 4 23

6 H(Pixels) + 49.5 46.875 1056 800 16 80 160 800 x 600

V(Lines) + 75.0 625 600 1 3 21

7 H(Pixels) +/- 57.283 49.725 1152 832 32 64 224 832 x 624

V(Lines) +/- 74.55 667 624 1 3 39

8 H(Pixels) - 65.0 48.363 1344 1024 24 136 160 1024 x 768

V(Lines) - 60.0 806 768 3 6 29

9 H(Pixels) - 78.75 60.123 1312 1024 16 96 176 1024 x 768

V(Lines) - 75.029 800 768 1 3 28

10 H(Pixels) +/- 100.0 68.681 1456 1152 32 128 144 1152 x 870

V(Lines) +/- 75.062 915 870 3 3 39

11 H(Pixels) +/- 92.978 61.805 1504 1152 18 134 200 1152 x 900

V(Lines) +/- 65.96 937 900 2 4 31

12 H(Pixels) + 108.0 63.981 1688 1280 48 112 248 1280 x 1024

V(Lines) + 60.02 1066 1024 1 3 38

13 H(Pixels) + 135.0 79.976 1688 1280 16 144 248 1280 x 1024

V(Lines) + 75.035 1066 1024 1 3 38

MODE

H / V

Sync

Polarity

Dot

Clock

Frequency

Total

Period

( E )

Video

Active

Time ( A )

Sync

Duration

( D )

Front

Porch

( C )

Blanking

Time

( B )

Resolution

- 7 -

LGE Internal Use Only

- 8 -

LGE Internal Use Only

# 2

# 3

# 4

Soft pad on the table.

# 1

Place the monitor face down on the cushion or soft cloth.

Disassemble back cove.

1.Remove the 4 serews.

2.Disassembly Stand.

1.Pull the front cover upward

2.Then,let the all latches are separated.

3.Put the front face down.

DISASSEMBLY-Set

- 9 -

LGE Internal Use Only

# 1-1 # 1-2

# 2

Separate stand body form the stand base .

DISASSEMBLY-Stand

Push the two latches on the bottom to the inside. (Reference the #1-2)

+ 20 hidden pages

LG Flatron L1742P, Flatron L1942P Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual