Sharp LC20A2M Schematic

TENTATIVE

SERVICE MANUAL

S00K2LC-20A2H

LCD COLOUR TELEVISION

LC-20A2M

MODEL

In the interests of user-safety (Required by safety regulations in some countries) the set should be restored to its original condition and only parts identical to those specified should be used.

LC-20A2M

CONTENTS

Page Page

IMPORTANT SERVICE SAFETY PRECAUTION......

» SPECIFICATIONS ............................................. 3

» OPERATION MANUAL ...................................... 4

» DIMENSIONS .................................................... 5

» REMOVING OF MAJOR PARTS ....................... 6

» TROUBLE SHOOTING TABLE .......................... 9

» ADJUSTMENT PROCEDURE......................... 12

» CHASSIS LAYOUT .......................................... 14

» BLOCK DIAGRAM........................................... 16

» DESCRIPTION OF SCHEMATIC DIAGRAM .. 18

» SCHEMATIC DIAGRAM .................................. 19

» PRINTED WIRING BOARD ASSEMBLIES..... 29

» PARTS LIST

ELECTRICAL PARTS .................................. 34

MAIN UNIT .................................................. 34

Y/C SEPARATION UNIT .............................. 38

TERMINAL UNIT ......................................... 40

INVERTER UNIT ......................................... 41

OPERATION UNIT....................................... 42

CABINET AND MECHANICAL PARTS ....... 42

SUPPLIED ACCESSORIES........................ 44

PACKING PARTS......................................... 44

» PACKING OF THE SET ................................... 45

The component parts of this model are par tially different depending on their suffix symbols. Bef ore servicing the units, be sure to check the suffix symbol on the model label that is applied on the back of the unit.

Example of suffix symbol:

LCD COLOUR TV MODEL LC-20A2M 13V 3.7A, 48W

SERIAL NO.

SHARP CORPORATION MADE IN JAPAN

SHARP CORPORATION

X xxxxxxxxx

Suffix "X" for Australlia

LC-20A2M

IMPORTANT SERVICE SAFETY PRECAUTION

Service work should be perfomed only b y qualified service technicians who are thoroughl y familiar with all safety checks and the servicing guidelines which follow:

WARNING

1. For continued safety, no modification of any circuit should be attempted.

2. Disconnect AC power before servicing.

CAUTION: FOR CONTINUED PROTECTION AGAINST A RISK OF FIRE REPLACE ONLY WITH SAME TYPE FUSE. F3701 (2.0A, 250V), F3702 (2.5A, 250V), F7751 (5.0A, 250V) FUSE.

BEFORE RETURNING THE RECEIVER (Fire & Shock Hazard)

Before returning the receiver to the user, perform the following safety checks:

1. Inspect all lead dress to make certain that leads are not pinched, and check that hardware is not lodged between the chassis and other metal parts in the receiver.

2. Inspect all protective devices such as non-metallic control knobs, insulation materials, cabinet backs, adjustment and compartment covers or shields, isolation resistor-capacitor networks, mechanical insulators and etc.

3. To be sure that no shock hazard exists, check for leakage current in the following manner.

• Plug the AC cord directly into a 110~240 volt A C outlet, and connect the DC power cable into the receiver's DC jack. (Do not use an isolation transformer for this test).

• Using two clip leads, connect a 50k ohm, 10 watt resistor paralleled by a 0.15µF capacitor in series with all exposed metal cabinet parts and a known earth ground, such as electrical conduit or electrical ground connected to an earth ground.

• Use an AC voltmeter ha ving with 5000 ohm per volt, or higher, sensitivity or measure the AC voltage drop across the resisor.

• Connect the resistor connection to all exposed metal parts having a return to the chassis (antenna, metal cabinet, screw heads, knobs and control shafts, escutcheon and etc.) and measure the AC voltage drop across the resistor. All checks must be repeated with the AC cord plug connection reversed. (If necessary, a nonpolarized adaptor plug must be used only for the purpose of completing these checks.) Any reading of 35V peak (this corresponds to 0.7 milliamp. peak A C .) or more is e xcessive and indicates a potential shock hazard which must be corrected before returning the monitor to the owner .

DVM

AC SCALE

50k ohms.

10W

0.15 µF

TEST PROBE

TO EXPOSED METAL PARTS

CONNECT TO KNOWN EARTH GROUND

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SAFETY NOTICE

Many electrical and mechanical parts in LCD television have special safety-related characteristics. These characteristics are often not evident from visual inspection, nor can protection afforded by them be necessarily increased by using replacement components rated for higher voltage, wattage and etc. Replacement parts which have these special safety characteristics are identified in this manual; electrical

and shaded areas in the

Schematic Diagrams

For continued protection, replacement parts must be identical to those used in the original circuit. The use of a substitute replacement parts which do not have the same safety characteristics as the factory recommended replacement parts shown in this service manual, may create shock, fire or other hazards.

components having such features are identified by “ å”

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Replacement Parts Lists

and

Specifications

LC-20A2M

Operation Manual

Main unit (front view)

Main unit (rear view)

Remote control

Dimensions

LC-20A2M

(Unit: mm)

LC-20A2M

REMOVING OF MAJOR PARTS

1. Detach the terminal cover.

2. Remove the four lock screws from the table stand.

3. Remove the four lock scre ws each from the left and right speakers. Disconnect the connectors and detach the speaker assemblies.

4. Remove the ten lock screws from the terminals.

5. Remove the five lock screws from the cabinet B.

6. Undo the nine hooks off the cabinet B: Press the hook 6-9

in this order. Detach the cabinet B.

7. Undo the six wire holders and peel off the 9 pieces of tape. Disconnect the connection cables. (Note: Some pieces of tape are located below the PWBs. To access such tape, detach the

PWBs, peel off the tape and disconnect the cables.)

8. Disconnect the connectors from the PWBs.

6-1

first and then the hooks

6-2

thru

Speaker (Right) Connection Cable

Terminal PWB Holder

Speaker Assembly (Right)

Cabinet B Cabinet A

SC1201

(MAIN Unit)

Tape

SC1202

P755

P754

P753

Tape

P701

P2001

P303

6-7

6-6

6-8

6-9

SC401

SC3401

SC3405

6-4

6-5

SC7001

(Y/C SEPARATION Unit)

P7102

P7101

P7301

P7305

(TERMINAL Unit)

P3701

6-3

P7753

(INVERTER Unit)

P7755

P7751

P3206

Speaker Assembly (Left)

Terminal Cover

6-2

6-1

Table Stand (Cover)

Table Stand

Speaker (Left)

Connection Cable

Tape

(OPERATION Unit)

P4004

Tape

9. Remove the four lock screws from the MAIN PWB.

10. Remove the four lock screws from the Y/C SEPARATION PWB.

11. Remove the three lock screws from the INVERTER PWB.

12. Remove the lock screw from the TERMINAL PWB and the lock screw from the grounding terminal. Detach the reinforcement plate too.

13. Remove the two lock screws from the LCD display unit.

14. Remove the three lock screws from the OPERATION PWB.

Y/C SEPARATION Unit

INVERTER Unit

TERMINAL PWB Assembly

MAIN Unit

LC-20A2M

LCD Display Unit

OPERATION Unit

Reinforcement Plate

Cabinet A

LC-20A2M

» Precautions in handling the LCD panels

1. Work in a clean room (with humidities below 50%).

2. Be sure to wear an anti-static armband.

3. Handle the panels on an electroconductive mat.

4. Be careful not to fall, shake and shock the panels.

15. Remove the four lock screws from the front of the LCD display unit and the three lock screws from its back. Detach the shielding plate.

16. Detach the two reflection sheets.

17. Detach the top and bottom fluorescent lamps.

18. Remove the photoconductive plate.

19. Detach the top and bottom reflection sheets.

20. Detach the ITO sheet.

21. Detach the diffusion sheet and reflection/deflection plate.

LCD Display Unit (Front)

Lamp Reflector (PSHEP0223CEZZ)

Photoconductive Plate

ITO Sheet

Fluorescent Lamp (Top) (KLMP-0101CEZZ)

Reflection Sheet (PSHEP0187CEZZ)

Reflection Sheet

(PSHEP0186CEZZ)

Fluorescent Lamp (Bottom) (KLMP-0102CEZZ)

Shielding Plate

LCD Display Unit

Diffusion Sheet

Reflection/deflection Plate

Lamp Reflector (Bottom)

(PSHEP0224CEZZ)

No picture

at all

Yes

Are inputs

and outputs

of IC802 as

specified?

Check all the settings on the microprocessor’s adjust process menu.

No picture

Check IC802

and its

peripheral

parts.

Yes

Are inputs

and outputs

of IC1201 as

specified?

Check

IC1201 and

its peripheral

parts.

Check LCD

panel voltage

and

waveform.

No TV and

VIDEO 1

output

Yes

Are inputs

and outputs

of IC402 as

specified?

Check IC402

and its

peripheral

parts.

Is input at pin

(73) of IC802

as specified?

Check IC802,

AV1 line and

their

peripheral

parts.

No TV

output

Yes

Are voltages

at pins (6),

(7) and (9) of

tuner as

specified?

Check the

power line.

Yes

Is output at

pin (19) of

tuner as

specified?

Check the

tuner and its

peripheral

parts.

Is input at pin

(1) of IC402

as specified?

Check the

line in

question.

Yes

Check IC402

and its

peripheral

parts.

Yes

Are pins (2)

and (4) of

IC402 at “H”

and “L”

respectively?

Are pins (65)

and (66) of

IC2001 at “H”

and “L”

respectively?

No VIDEO

1 output

Yes

Is input at pin

(1) of IC402

as specified?

Check the

line in

question.

Yes

Are pins (2)

and (4) of

IC402 both at

“L”?

No VIDEO

2 output

Is input at pin

(74) of IC802

as specified?

Check J3403,

AV2 line and

their

peripheral

parts.

No S

VIDEO

output

Are inputs at

pins (71) and

(72) of IC802

as specified?

Check

SC3301, SY

line, SC line

and

peripheral

parts.

COMPONENT

output

Is input at

pins (4), (5),

(6) and (75)

of IC802 as

specified?

Check J3405,

DVD-Y line,

CB line, CR

line and

peripheral

parts.

Are pins (65)

and (66) of

IC2001 both

at “L”?

Check IC402

and its

peripheral

parts.

Yes

Check the

line in

question.

Yes

Check the

line in

question.

TROUBLE SHOOTING TABLE

LC-20A2M

No picture and sound

No colour

No TV colour

No S-VIDEO colour

Yes

Do F3701 and F3702

function?

Check all the settings on the microprocessor’s adjust process menu.

Are secondary outputs

(+38V, +16V, +9V, +5V, -8V)

of T701 as specified?

Yes

Are the oscillation waveform

at T701’s primary side as

specified?

Yes

Disconnect F3701 and

F3702. Is the load side

short-circuited?

Yes

Is any of T701’s primary side,

Q701, Q710 and S4701

short-circuited?

Check J3701, its peripheral

parts and connection cable.

Replace F3701 and F3702.

Check S4701 and

connection cable.

Check the secondary-side

load of T701.

Fluorescent lamp

Yes

Does F7751 function?

Yes

Is Pin (34) of IC1201 at “H”?

Yes

Are the oscillation waveforms

at the primary side of T7751-6

as specified?

Yes

Replace F7751.

Is input at pin (71) of IC802

as specified?

Check SC3301, SC line and

peripheral parts.

Yes

Check the line, IC1201 and

its peripheral parts.

Check Q7751-5, T7751-6

and their peripheral parts.

Replace the fluorescent lamp

and check the oscillation

waveform again.

No VIDEO colour

Check all the settings on the microprocessor’s adjust process menu.

No COMPONENT colour

Is input at pins (4) and (6) of

IC802 as specified?

Check J3405, CB line, CR

line and peripheral parts.

TROUBLE SHOOTING TABLE (Continued)

No sound

from

speakers

Yes

Is pin (53) of

IC2001 at “L”?

Check all the settings on the microprocessor’s adjust process menu.

No sound

Are outputs at

pins (1) and (7)

of IC903 as

specified?

Yes

Are inputs and

outputs of

IC303 as

specified?

Yes

Are inputs at

pins (11) and

(16) as well as

outputs at pins

(3) and (5), all

of IC7305, as

specified?

Muting effect is

on. Check the

FSMU line.

Check IC901,

IC903 and their

peripheral

parts.

Check IC303

and its

peripheral

parts.

Check the line

in question,

IC7305 and its

peripheral

parts.

Yes

Check the

speakers and

their peripheral

parts.

No sound

from

headphone

Yes

Is pin (55) of

IC2001 at “L”?

Check the

headphone and

its peripheral

parts.

Check Q306,

J4001 and their

peripheral

parts.

No sound

from output

line

Yes

Is pin (52) of

IC2001 at “L”?

Are outputs at

pins (1) and (7)

of IC902 as

specified?

Yes

Check the line

in question.

Check the

LMUTE line.

Check IC902

and its

peripheral

parts.

TV sound

failure

Yes

Is output at pin

(16) of tuner as

specified?

Is input at pin

(60) of IC901

as specified?

Check the

tuner and its

peripheral

parts.

Check IC901,

Q3301, Q3204,

Q3205 and

their peripheral

parts.

TROUBLE SHOOTING TABLE (Continued)

LC-20A2M

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