Mitsubishi LT-3050, LT-3040, LT-3020, LT-2240, LT-2220 Service Manual

MITSUBISHI ELECTRIC

2003-2004

Service Manual

LIQUID CRYSTAL DISPLAY TELEVISION

LT-2220 LT-2240 LT-3020 LT-3040 LT-3050

CAUTION:

Before servicing this chassis, it is important that the service person read the "SAFETY PRECAUTIONS" and "PRODUCT SAFETY NOTICE" contained in this manual.

SPECIFICATIONS

• Power : [LT-2220, LT-2240] AC ADAPTOR

In - AC 120V, 60Hz; Out - 20VDC 6.0A

: [LT-3020, LT-3040, LT-3050] 120V, 60Hz, 2.2A

• LCD Panel : Resolution - 1280X768 : Pixel Pitch - [LT-2220, LT-2240] 0.375mm

[LT-3020, LT-3040, LT-3050] 0.5025mm

• Analog Inputs : VHF/UHF 75Ω unbalanced : Two A/V Inputs (Composite or S-Video)

L-R Audio

: Two Component Video Inputs (480i/480p/

720p/1080i) L-R Audio : PC Input - 60Hz (VGA,S-VGA,XGA,W-XGA) : PC Audio - 3.5mm Mini-Jack

• Digital Input : MonitorLink™/DVI (Video Sources Only) L-R Audio (Analog)

: MonitorLink™ Control/RS-232C

• Audio Outputs : L-R Audio Output (Fixed/Variable)

: Headphone Jack (Variable) 3.5mm

• Tuning : NTSC 181Channel Analog Cable

• Frequency Range : VHF 54 ~ 470MHz

UHF 470 ~ 806MHz

• Speakers : [LT-2220, LT-2240] Left & Right (2 X 2.3W) Sub (3.4W) : [LT-3020, LT-3040, LT-3050] Left & Right (2 X 3.5W) Sub (6W)

• Weight / Cabine t Dim ensions With Stand: Height Width Depth Weight

[LT-22XX] 20-1/4" 22-3/4" 11-7/8" 36.6 lbs [LT-30XX] 25-3/8" 29-3/4" 11-7/8" 54.3 lbs

W/O Stand: Height Width Depth Weight

[LT-22XX] 18-5/8" 22-3/4" 4" 19.8 lbs [LT-30XX] 23-1/4" 29-3/4" 5" 37.5 lbs

• Weight and dimensions shown are approximate.

• Design specifications are subject to change without notice.

MITSUBISHI DIGITAL ELECTRONICS AMERICA, INC.

9351 Jeronimo Road, Irvine, CA 92618-1904

MODELS: LT-2220 / LT-2240 / LT-3020 / LT-3040 / LT-3050

CONTENTS

INTRODUCTION .................................................................................................................................. 5

PRODUCT SAFETY NOTICE ............................................................................................................... 5

SAFETY PRECAUTIONS ..................................................................................................................... 5

DISASSEMBLY

LT-22XX ............................................................................................................................................. 7

LT-30XX ........................................................................................................................................... 13

ELECTRICAL ADJUSTMENTS

Initial Setup .................................................................................................................................... 21

CIRCUIT EXPLANATIONS & BLOCK DIAGRAMS

Circuit Explanations ....................................................................................................................... 23

Block Diagrams.............................................................................................................................. 29

TEST POINT LOCATIONS AND DESCRIPTIONS

PWB-SET Test Point Locations and Description ............................................................................ 33

PWB-MAIN Test Point Locations and Description .......................................................................... 35

TROUBLESHOOTING

LT-22XX Power Troubleshooting ...................................................................................................... 37

LT-30XX Power Troubleshooting ...................................................................................................... 39

Video Troubleshooting .................................................................................................................... 41

Audio Troubleshooting .................................................................................................................... 51

Remote Control & Front Switch Troubleshooting ............................................................................ 53

REPLACEMENT PARTS

Replacement Parts List .................................................................................................................. 55

INTERCONNECT WIRING DIAGRAM

Page 3

MODELS: LT-2220 / LT-2240 / LT-3020 / LT-3040 / LT-3050

Page 4

MODELS: LT-2220 / LT-2240 / LT-3020 / LT-3040 / LT-3050

PRODUCT SAFETY NOTICE

Many electrical and mechanical parts in television receivers have special safety related characteristics. These characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily be obtained by using replacement components rated for higher voltage, wattage, etc.

Replacement parts which have special safety characteristics are identified in this service manual.

The replacement for any safety part should be identical in value and characteristics.

SAFETY PRECAUTIONS

NOTICE: Observe all cautions and safety related notes located inside the receiver cabinet and on the

receiver chassis.

WARNING:

1. Operation of this receiver outside the cabinet or with the cover removed presents a shock hazard from the receiver's power supplies. Work on the receiver should not be attempted by anyone who is not thoroughly familiar with the precautions necessary when working on high voltage equipment.

2. Do not install, remove or handle the LCD panel in any manner unless shatterproof goggles are worn. People not so equipped should be kept away while the panel is being handled. Keep the panel away from the body while handling.

3. When service is required, observe the original lead dress. Where a short-circuit has occurred, replace those components that indicate evidence of overheating.

Leakage current check

Before returning the receiver to the customer, leakage current should be measured using following methods.

1. Cold Check

With the alternating current (AC) plug removed from the AC source, place a jumper across the two AC plug

prongs. Connect one lead of an ohm meter to the AC plug and touch the other lead to each exposed metal part (i.e. antennas, handle bracket, metal cabinet, screw heads, metal overlay, control shafts, etc.), particularly any exposed metal part that has a return path to the chassis. The resistance of the exposed metal parts having a return path to the chassis should be a minimum of 1Mega Ohm. Any resistance below this value indicates an abnormal condition and requires corrective action.

2. Hot Check ...Use the circuit shown below to perform the hot check test.

1. Keep switch S1 open and connect the receiver to the measuring circuit. Immediately after

connection, and with the switching devices of the receiver in their operating positions, measure

the leakage current for both positions of switch S2.

2. Close switch S1, energizing the receiver. Immediately after closing switch S1, and with the

switching devices of the receiver in their operating positions, measure the leakage current for both positions of switch S2. Repeat the current measurements of items 1 and 2 after the receiver has

reached thermal stabilization. The leakage current must not exceed 0.5 milliampere (mA).

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