Sharp LC-20B4M Schematic

LC-20B4M

SERVICE MANUAL

S43A4LC-20B4M

LCD COLOUR TELEVISION

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.

CONTENTS

» IMPORTANT SERVICE SAFETY PRECAUTION ........................................................................................2

» SPECIFICATIONS ........................................................................................................................................4

» OPERATION MANUAL .................................................................................................................................5

» DIMENSIONS ...............................................................................................................................................7

» REMOVING OF MAJOR PARTS ..................................................................................................................8

» ADJUSTING PROCEDURE OF EACH SECTION .....................................................................................12

» TROUBLE SHOOTING TABLE ...................................................................................................................18

» CHASSIS LAYOUT .....................................................................................................................................22

» BLOCK DIAGRAM......................................................................................................................................24

» OVERALL WIRING DIAGRAM ...................................................................................................................26

» DESCRIPTION OF SCHEMATIC DIAGRAM .............................................................................................28

» SCHEMATIC DIAGRAM .............................................................................................................................29

» PRINTED WIRING BOARD ASSEMBLIES................................................................................................56

» REPLACEMENT PARTS LIST....................................................................................................................68

» PACKING OF THE SET..............................................................................................................................81

LC-20B4M

Page

SHARP CORPORATION

LC-20B4M

2

2

2

IMPORTANT SERVICE SAFETY PRECAUTION

Ë

Service work should be performed only by qualified service technicians who are
thoroughly 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 F3301(2A, 250V), F3302(1.25A, 250V),
F6700 (1.25A, 250V), F6701 (1.25A, 250V), F6702
(1.25A, 250V), F6703 (1.25A, 250V) AND F6704
(1.25A, 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, 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 resistor.

• 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, 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 0.75V peak (this corresponds to 0.5
mA. peak AC.) or more is excessive and indicates a
potential shock hazard which must be corrected before
returning the monitor to the owner.

DVM

AC SCALE

50k ohm

10W

0.15 µF

TEST PROBE

TO EXPOSED
METAL PARTS

CONNECT TO
KNOWN EARTH
GROUND

234567890123456789012345678901212345678901234567890123456789012123456789012345678901234567890121

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, 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 b y “ å”

234567890123456789012345678901212345678901234567890123456789012123456789012345678901234567890121

234567890123456789012345678901212345678901234567890123456789012123456789012345678901234567890121

2

Replacement Parts Lists and

LC-20B4M

Precautions for using lead-free solder

1 Employing lead-free solder

"All PWBs" of this model employs lead-free solder. The LF symbol indicates lead-free solder, and is attached on
the PWBs and service manuals. The alphabetical character following LF shows the type of lead-free solder.
Example:

L Fa

Indicates lead-free solder of tin, silver and copper.

2 Using lead-free wire solder

When fixing the PWB soldered with the lead-free solder, apply lead-free wire solder. Repairing with conventional
lead wire solder may cause damage or accident due to cracks.
As the melting point of lead-free solder (Sn-Ag-Cu) is higher than the lead wire solder by 40°C, we recommend
you to use a dedicated soldering bit, if you are not familiar with how to obtain lead-free wire solder or soldering bit,
contact our service station or ser vice branch in your area.

3 Soldering

As the melting point of lead-free solder (Sn-Ag-Cu) is about 220°C which is higher than the conventional lead
solder by 40°C, and as it has poor solder wettability, you may be apt to keep the soldering bit in contact with the
PWB for extended period of time. However, Since the land may be peeled off or the maximum heat-resistance
temperature of parts may be exceeded, remov e the bit from the PWB as soon as you confirm the steady soldering
condition.
Lead-free solder contains more tin, and the end of the soldering bit may be easily corroded. Make sure to turn on
and off the power of the bit as required.
If a different type of solder stays on the tip of the soldering bit, it is allo y ed with lead-free solder. Clean the bit after
every use of it.
When the tip of the soldering bit is blackened during use, file it with steel wool or fine sandpaper.

Be careful when replacing parts with polarity indication on the PWB silk.

Lead-free wire solder for servicing

Part No, ★ Description Code
ZHNDAi123250E J φ0.3mm 250g(1roll) BL
ZHNDAi126500E J φ0.6mm 500g(1roll) BK
ZHNDAi12801KE J φ1.0mm 1kg(1roll) BM

3

LC-20B4M

SPECIFICATIONS

MODEL

ITEMS

LCD panel
Number of dots

Video colour systems

TV Standard

TV T uning System

TV
FUNCTION

4-LINE DIGITAL COMB FILTER
Brightness
Lamp life
Viewing angles
Audio output
Speakers

Terminals

Headphone jack
OSD LANGUAGE
Power requirement
Weight
Accessories

STEREO/BILINGUAL
Universal R/C for TV only
AUTO PRESET
CATV

AV2 IN/OUT

Component

LC-20B4M

19.7" (50 cm) Advanced Super
View & BLACK TFT LCD

921,600 dots VGA
World multi system
I/DK/M/BG
Auto preset tuning
NICAM-BG, I, DK/IGR-BG
Yes
Yes
S1~S41 ch. Hyper Band
Yes
430 cd/m
60,000 hours
H: 170° V: 170°

2.5 W × 2
5 cm ø, 2 pcs.

AV1

Composite Video, S-Video, Audio
Composite Video/Audio
Y, P

3.5 mm ø jack (Rear)
English/Chinese/Arabic

DC 13V, AC10-240V, 50/60Hz

8.7 kg w/o accessories
Wireless Remote Control, Batteries, Cable clamps, AC adapter, AC cord,

Operation manual, Antenna cable

2

B

, PR/Audio

As a part of policy of continuous improvement, SHARP reserves the right to make design and specification
changes for product improvement without prior notice. The performance specification figures indicated are nominal
values of production units. There may be some deviations from these values in individual units.

4

CH

MENU

TV/VIDEO MAIN POWER

PRESET

1

2

VOL

Upper control panel

MENU

MAIN POWER

TV/VIDEO

CH( )/( )

VOL (

-

)/(+)

P

O

W

E

R

S

L

E

E

P

SLEEP indicator

The SLEEP indicator lights up red when the

SLEEP TIMER is set to on.

Remote sensor window

Power/Standby indicator

A green indicator lights when the power is on

and a red indicator lights when in the standby

mode (the indicator will not light when the

main power is off).

Note:

•

TV/VIDEO, CH (

)/( ), and VOL (–)/(+) on the main unit have the same functions as the same buttons on the remote

control. Fundamentally, this operation manual provides a description based on operation with the remote control.

Main unit (front view)

* The examples used throughout this manual are based on the LC-20B4M

model.

Speaker

To change the vertical angle of the

LCD TV set, tilt the screen up to 5

degrees forward or 10 degrees

backward. The TV set can also be

rotated 25 degrees to right and left.

Please adjust the angle so that the

TV set can be watched most

comfortably.

Main unit (rear view)

V
O
L

C
H

ME
N
U

T
V
/V
ID

E
O
M
AI
N
P
O
W
E
R

A

N

T

.

V

IDE

O

S

-

VIDE

O

A

U

D

I

O

L

R

H

E

A

D

P

H

O

N

E

A

V

-

IN

1

VIDEO

AV-IN1

AUDIO (L)

AUDIO (R)

S-VIDEO

HEADPHONE

Antenna terminal

POWER INPUT

DC 13V

V

I

DE

O

A

U

D

I

O

L

Y

P

B

P

R

R

A

U

D

I

O

L

R

C

O

M

P

O

N

E

N

T

A

V

-

IN2

/

O

U

T

Y

VIDEO

AV-IN2/OUT

COMPONENT

AUDIO (L)

AUDIO (R)

P

B

P

R

AUDIO (L)

AUDIO (R)

Carrying handle

P

O

W

E

R

I

N

PU

T

D

C

13

V

U

S

E

TH

E

SU

PP

L

I

E

D

A

C

AD

A

PT

E

R

.

(

P

AR

T

N

O

.

L

O

C

A

T

ED

O

N

T

H

E

M

O

D

E

L

L

A

BE

L

.

)

How to adjust the angle

Tilt the display by grabbing onto the

carrying handle while securely

holding down the stand with your

other hand.

OPERATION MANUAL

LC-20B4M

5

LC-20B4M

Remote control

MENU

Displays the TV menu.

SUBTITLE

Displays the Teletext

Subtitle directly.

HOLD

Temporarily holds the

current Teletext page.

MUTE

Switches the sound on and off.

Yellow

Cyan

CHANNEL SELECT

OK

VOL (+)/(

-

)

Flashback

Returns to the previous

channel.

Red

Upwards/ Downwards

Selection, zoom display

function (Teletext mode)

END

TEXT

Displays the Teletext mode

screen.

POWER

MPX

Switches Audio

mode.

REVEAL

Displays hidden information

such as solutions to riddles

and puzzles.

Right / Left Selection

SUBPAGE

Displays the Teletext

Subpage directly.

TV/VIDEO

Switches the input source

between AV1, AV2, COMPONENT

and TV mode.

BRIGHT

Selects the brightness

of the display.

Green

CH

MENU

E

TV/VIDEO

R

E

V

E

AL

HOLD

END

M

MENUSOUND

SU

BTITLE

SUBPAGE

T

E

X

T

ROTATE

W

IDE

T

CHVOL

MENU

SLEEP DIS.MODE

OKMPX

SUBTITLE END

HOLD

SUBPAGE

REVEAL

TEXTBRIGHT

TV/VIDEOPOWER

SLEEP

DIS.MODE

DISPLAY

Press....Displays receiving channel

for 10 seconds. Channel

indication reduces in size

after about 10 seconds.

Press again...Removes display.

CH ( )/( )

Selects next higher channel.

Selects next lower channel.

Batteries for Remote Control

Before using the LCD TV set for the first time, install two (“AAA” size, UM/SUM-4) batteries (supplied).

When the batteries become depleted and the remote control fails to operate, replace the batteries with

new (“AAA” size, UM/SUM-4) batteries.

1

Open the battery

cover.

2

Insert two (“AAA” size,

UM/SUM-4) batteries.

3

Close the battery

cover.

Slide the cover while

pressing the (

) part.

Position the positive and

negative ends of the

batteries as indicated in the

compartment.

Engage the claw on the

cover into the battery

housing and slide shut.

6

DIMENSIONS

CHVOL T V/VIDEOMENU MAIN POWER

2

1

PRESET

420

630

Unit: mm

68.6

76.1

LC-20B4M

76.1

110.7

471.5

470.3

381.5

193.5 188

VIDEO

AV-IN 2/OUT

AUDIO

COMPONENT

AUDIO

300.8

403.3

POWER

SLEEP

VIDEO

AV-IN1
L

AUDIO

R

100

51.5

100

L

R

Y

P

B

R

P

L

R

S-VIDEO

HEAD

PHONE

ANT.

USE THE SUPPLIED
AC ADAPTER.
(PART NO. LOCATED ON
THE MODEL LABEL.)

POWER INPUT

DC13V

249.6

7

LC-20B4M

SC1204

SC3403

REMOVING OF MAJOR PARTS

1. Remove the stand fixing screws (4 pcs.).

2. Remove the two terminal covers.

3. Remove the terminal section fixing screws (2 pcs.).

4. Remove the cabinet B fixing screws (12 pcs.).

5. Remove the cabinet B after opening from the direction of an arrow.

6. Remove the reinforcement angle fixing screws (4 pcs.).

7. Release peel off the tape.

8. Detach the connector from each PWB.

4

Terminal Cover (S)

2

4

Cabinet A

R

E

W

O

P

N

I

A

M

O

E

D

I

V

/

V

T

U

N

E

M

H

C

L

O

V

2

3

5

5

Cabinet B

1

4

Terminal Cover (L)

Stand

Reinforcement Angle

Operation PWB

8

8

8

SC1204

SC1204

SC1202SC1203

8

Main PWB

8

P701

P2001

P4001

SC2002

8

SC3403

SC3403

Tuner PWB

8

8

P6705

Inverter-A

8

PWB

6

8

8

7

Tape

R/C, LED PWB

P4004

8

P6706

Inverter

8

8

-B PWB

P3701

P3301

8

P3502

P3603P3603

8

P3604

8

P3302

P3302

8

P3601

P3602

8

8

9. Remove the inverter-A PWB fixing screws (2 pcs.).

12

9

10

Inverter-A
PWB

Main PWB

Chassis Frame

Chassis Frame Cover

Tuner
PWB

Inverter-B
PWB

Operation PWB

14

13

R/C, LED PWB

11

12

12

10. Remove the inverter-B PWB fixing screw (1 pc.).

11. Remove the main PWB fixing screws (3 pcs.).

12. Remove the tuner PWB fixing screws (3 pcs.) and detach the chassis frame cover fixing hooks.

13. Remove the R/C, LED PWB fixing screws (2 pcs.).

14. Remove the operation PWB fixing screws (2 pcs.).

LC-20B4M

9

LC-20B4M

» 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 electro-conductive mat.

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

15. Remove the LCD panel unit fixing screws (4 pcs.).

16. Remove the ITO earth spring fixing screw (1 pc.).

17. Remove the reflection/deflection, prism, diffusion, ITO sheets and diffusion panel.

18. Remove the lamp fixing holder fixing screws (6 pcs.).

19. Detach the lamp unit-A/B.

20. Remove the reflection mirror fixing screws. (6 pcs.).

Back shield
(PSLDM4685CEFW)

Diffusion Panel
(PCOVU0107CEZZ)

ITO Sheet
(PSHEP0289CEZZ)

Prism Sheet
(PSHEP0287CEZZ)

20" LCD Panel Unit

15

15

Reflection Mirror
(PMiR-0296CEZZ)

Lamp Fixing Holder
(LHLDZ2176CEZZ)

18

17

Diffusion Sheet
(PSHEP0288CEZZ)

Reflection/Deflection Sheet
(PSHEP0286CEZZ)

18

16

ITO Earth Spring
(MSPRP1220CEFW)

21

19

Lamp Unit-A
(KLMP-0124CEZZ)

Lamp Unit-B
(KLMP-0125CEZZ)

Lamp Fixing Holder
(LHLDZ2176CEZZ)

10

LC-20B4M

Precautions at the time of the side B(back) service of digital unit.

1. Remove only SC2002 of the FFC for connection between Main unit (SC2002) and Tuner unit(SC3403), and con­nect the extended cable (QCNW-A556WJZZ) for service.

2. Remove the FFC for connection between Main unit (SC1204) and LCD panel unit, and connect the extended
cable (QCNW-A553WJZZ) for service.

3. Remove the FFC for connection between Main unit (SC1203) and LCD panel unit, and connect the extended
cable (QCNW-A556WJZZ) for service.

4. Remove the FFC for connection between Main unit (SC1202) and LCD panel unit, and connect the extended
cable (QCNW-A555WJZZ) for service.

5. Remove only P701 of the Connecting Cord f or connection between Main unit (P701) and Tuner unit (P3701), and
connect the extended cable (QCNW-B194WJZZ) for service.

6. Remove the main unit fixing screws (3 pcs.), a substrate is reversed.

Main PWB
(Side B)

6

3

SC1202

2

SC1203

SC1204

4

Main PWB

5

P701

P2001

1

SC2002

Tuner PWB

SC3403

P3701

Step Part No. Description

1 QCNW-A556WJZZ Extension Cable 50-pin Main (SC2002)-Tuner (SC3403)
2 QCNW-A553WJZZ Extension Cable 30-pin Main (SC1204)-LCD Panel
3 QCNW-A556WJZZ Extension Cable 50-pin Main (SC1203)-LCD Panel
4 QCNW-A555WJZZ Extension Cable 20-pin Main (SC1202)-LCD Panel
5 QCNW-B194WJZZ Extension Cable 12-pin Main (P701)-Tuner (P3701)

11

LC-20B4M

ADJUSTING PROCEDURE OF EACH SECTION

The best adjustment is made before shipping. If any position deviation is found or after part replace is performed, adjust
as follows.

Preparation for Adjustments

Use the exclusive-use AC adapter or stable DC power supply.

AC adapter: UADP-0241CEPZ
DC power supply: 13 ± 0.5V 5.4A

1. Adjustment Procedure

1-1. Adjusting the checker

Turning on the power (initialization) → Setting the model and size in inches → Transferring the model-specified
data to the E2PROM (I2C) → Calling the adjustment process mode → Starting the adjustment (+B adjustment)

1-2. Adjusting the finish process

Reassembling the set → Turning on the power → Calling the adjustment process mode (using the remote
controller) → Adjusting the counter bias, TV contrast and white balance

2. Calling the MAIN adjustment process mode

There are the following two ways to choose from.

• Set the Pin (81) (KEY4) or Pin (82) (KEY5) of IC2001 (microprocessor) to "L", turn on the power.

• For servicing, hold down the "TV/VIDEO" and "MENU" keys at once, and turn on the "POWER" switch. (Make

sure the process mode "K" appears at the top left of the screen.) Then press the "CH (Ù)" and "VOL (–)" keys
at once. (Make sure the adjustment process mode screen shows up.) To quit this mode, turn off the power. (Or
turn off the "POWER" switch or use the remote controller’s "OFF" key.)

3. Using the keys for the adjustment process

Selecting a reception channel

• Using the "CH (ù)/(Ù)" key, turn up and down reception (broadcasting) channels.
Just click on the key, and channels are selected on by one.
Hold down the key, and the next receivable channel is searched up and down.

• Adjustment items
Adjust each of the items by using the "MENU", "CURSOR UP/DOWN" and "VOL (+)/(–)" keys (on the set or on
the remote controller).

• Select an adjustment item using the "CURSOR UP/DOWN" key.

• An adjustment item is toggled on and off by activating the MENU SELECT key (next item).

Let’s suppose that the item at the bottom of a page is now selected. When the "MENU" key is activated here, the
item at the top of the next page will be selected.

4. Initialization

4-1. Set pins (81) and (82) of IC2001 (microprocessor) to GND. Turn on the power.
4-2. A model number is automatically selected. Make sure "A640M" is selected.
4-3. Select the inch size (20).

12

LC-20B4M

5. Adjustment

5-1. +B adjustment (R3714 Variable resistor)

1) Receive the colour bar signal.

2) Adjust the voltage at pin (4) of P3701 to 5.00 ± 0.02 V.
Note: The 5.0 V level is used as reference for all the line voltages. Make this adjustment as precisely as

possible.

5-2. Counter bias adjustment: COM BIAS on page 2

Adjust the "COM BIAS" setting until the contrast gets optimum (the black portion blackest). The adjustment
guideline is around 98.

5-3. TAMP adjustment

1) Feed the colour bar pattern signal.

2) See if the "Y" reading on adjustment process page 2 is within the range shown below. If not, adjust the

"NTSC TAMP" setting to bring the "Y" reading within the specified range.

Model LC20B4M

Adjustment value 187~202

3) If the "NTSC TAMP" setting has been readjusted, write down its new setting in the "PAL TAMP" and

"SECAM TAMP" items manually.

(Page 2 of adjustment process OSD)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
0
1
2
3
4
5
6
7

2

COM B I AS

TAMP L 817

YD TA

TAMP
NTSC TAMP
PAL TAMP 26
SECAM

A

H

TAMP

Y Data

(White 75%)

98

918
022

26

2

6

5-4. White balance adjustment

1) Feed the monoscope pattern signal.

2) Adjust the "RCUTOFF" and "BCUTOFF" settings on adjustment process page 3 to achieve the color at the
same level as with the standard set.

13

LC-20B4M

5-5. Other adjustments (SOUND, VPC, DPS, DAC, TUNER, OTHERS, TEXT)

1) Move the cursor to a desired item on page 4 of adjustment process menu. Press the CURSOR LEFT/
RIGHT keys, "VOL (+)/(–)" keys or OK key to select the item.

4
I2C DATA 000000000000
I2C DATA WAIT
SOUND
VPC
DPS
DAC
TUNER
OTHERS
TEXT

2) The adjustment process menu of the item appears on the screen. The settings are now ready to change.

Screen with SOUND selected

SOUND1
VOLUME 0
AVC OFF
MSP DATA 0000000000
MSP DATA WAIT
0018H ST 1D
ONTA 1
CARRIER MUTE ON
SP TEST OFF

3) To go back to page 4 of adjustment process menu, press the FLASHBACK key on the remote controller.

5-6. Writing the model-by-model data

For the Ver. 0.96A (P.P.) /1.00A (1st~) microprocessor, get it initialized first and then make the settings, listed
below, on it. (The microprocessor version is indicated at the bottom of Adjustment Process Page1.)

Ver. 0.96A/1.00A data reprogramming (INCH SIZE [20] , MODEL:A640M)

Adjustment process page Item OSD settings
DPS01 N358 BRIGHTNESS +15 → -16
DPS16 PAL BRIGHTNESS +10 → -21
DPS21 SECAM BRIGHTNESS +10 → -21
DPS26 PAL60 BRIGHTNESS +5 → -26
DPS31 N443 BRIGHTNESS 0 → -31
DPS45 DPS NLC A6 E4 → FF
TEXT2 TEXTMIX CTI7D 16 → 0
TEXT3 TEXTALL BRT -55 → -40

TEXTALL CON 27 → 28

TEXT6 TEXTALL LTI 139 → 129

TEXTMIX LTI 139 → 129
TEXTALL LMIX78 66 → 79
TEXTMIX LMIX78 66 → 79

14

6. Lamp error detection

6-1. Functional description

This LCD colour television has a function (lamp error detection) to be turned OFF automatically for safety
when the lamp or lamp circuit is abnormal.
If the lamp or lamp circuit is abnormal, or some other errors happen, and the lamp error detection is
executed, the followings occur.
1 The main unit of television is turned OFF 5 seconds after it is turned ON. (The power LED on the front side

of TV turns from green to red.)

2 If the situation 1 happens 5 times sequentially, television can not be turned ON. (The power LED remains

red.)

6-2. Countermeasures
6-2-1. Check when turning OFF the lamp error detection

When television is turned OFF by the lamp error detection mentioned above, it enters the adjustment
process with the power LED red. Entering the adjustment process turns OFF the error detection and
turns ON TV.
This enables the operation check to detect errors in the lamp or lamp circuit.
Check whether "ERROR NO RESET" on line 4, page 1 of the adjustment process is 1 or more. If it is 1 or
more, it indicates the lamp error detection was executed.

6-2-2. Resetting of the lamp error count

After confirming that the lamp or lamp circuit is normal, reset the lamp error count. Select "ERROR NO
RESET" on line 4, page 1 of the adjustment process and set the number to 0 using the volume button.

LC-20B4M

Page 1 of the adjustment process

1

M O D E L A640M
I N C H S I Z E 20
E R R O R N O R E S E T 5
P U B L I C M O D E ON
E X T C O N T R O L OFF
V P C S H A R P N E S S ON
V P C F P 2 F H R E A D OFF
E X T M O D E UART
U P D A T E M O D E NORMAL
T E X T R E S E T OFF

V E R R O M 1. 0 0 G AI B U 0. 0 0 0

Reset 0

Afterwards, perform the operation check to confirm that the lamp error detection does not function.

15

LC-20B4M

7. Public mode

• How to enter into PUBLIC MODE

1. Turn off TV by pressing MAIN POWER switch.

2. While pressing "VOL(+)" key and "CH(ù)" key at the same time, press MAIN POWER switch for more than
2 seconds.
TV will turn on, and you will see the screen display a setting of PUBLIC MODE.

• Setting screen of “PUBLIC MODE”

PUBLIC MODE
MAXIMUM VOLUME [ 60]
VOLUME FIXED [VARIABLE]
REMOTE CONTROL [RESPOND]
USER CONTROL [RESPOND]
ON SCREEN DISPLAY [YES ]
START MODE [NORMAL ]
INPUT MODE FIXED [VARIABLE]
SOUND ONLY MODE [NO ]
RESET
ENTER

1 ↔ 2 ··· ↔ 59 ↔ 60
VARIABLE ↔ FIXED
RESPOND ↔ LIMITED ↔ NO RESPOND
RESPOND ↔ NO RESPOND
YES ↔ NO
NORMAL ↔ AV1 ↔ COMPONENT ↔ CH1 ↔ CH2
VARIABLE ↔ FIXED
NO ↔ YES

↔ CH99 ↔ CH0

...

↔ CH98

Factory setting

Adjust setting

1. You can select each item of functions by pressing cursor UP/DOWN keys or CH(ù)/(Ù) Keys on the remote
control or CH(ù)/(Ù) keys on the LCD TV. The letter of selected item turns to yellow colour when you selected
it.

2. The setting position of each item of functions are made by pressing cursor RIGHT/LEFT keys on the remote
control or VOL (+)/(–)keys on the LCD TV.

3. Select ENTER position after you set all functions, and press cursor RIGHT/LEFT keys on the remote control
or VOL(+)/(–)keys on the LCD TV for confirmation.
Unless otherwise you make ENTER confirmation, the settings will not be memorized.

• 6-functions of Public Mode settings expand for public application

1. MAXIMUM VOLUME (1—————60)
You can set the maximum volume at your desire level.

2. VOLUME FIXED (VARIABLE / FIXED)
You can fix the sound volume at your desire level.
When you set to "FIXED", the sound volume which you just set is fixed.

3. REMOTE CONTROL (RESPOND / LIMITED)
If you set "LIMITED", remote control keys of POWER, CH(ù)/(Ù), VOL(–)/(+) and BRIGHT keys are
responded, but other keys are not responded.
This is a position that you can not make MENU adjustments.

4. USER CONTROL (RESPOND / NO RESPOND)
"NO RESPOND" means that the TV does not respond when you press a user control buttons except main
power button on the main unit.

5. ON SCREEN DISPLAY (YES / NO)
If you set "NO" position, OSD will not appear.

6. START MODE (NORMAL ↔AV1 ↔COMPONENT↔CH1↔CH2

...

↔CH98↔CH99↔CH0)
When any other item than "NORMAL" has been selected, the set gets started in the selected input mode or
channel at the next switch-on.

7. INPUT MODE FIXED (VARIABLE↔FIXED)
(* This item cannot be selected if the start mode is "NORMAL".)
If "FIXED" has been selected, any channels and input modes other than those selected in the start mode cannot
be picked up.

16

LC-20B4M

8. SOUND ONLY MODE (NO↔YES)
(* This item cannot be selected if "NO" appears on the on-screen display.)
Let's suppose that this item has been selected and the BRIGHT key on the remote control has been pressed.
The item "BRIGHTNESS [OFF]" can now be selected next to the item "BRIGHTNESS [DARK]".

Screen with "BRIGHTNESS [OFF]" selected

Count-down started from 5

BRIGHTNESS [OFF] TURNS OFF IN 5 SECS.

Five seconds later, the screen shuts off and the sound alone is heard.
Once in this mode, no picture but the OSD appears. But the channels and sound volume can still be changed.

To quit this mode, press the BRIGHT key on the remote control again and select any item other than
"BRIGHTNESS [OFF]".

9. RESET
You can cancel all Public Mode settings. (It returns to the factory setting.)

10.ENTER
You make sure after you have specified all functions, then press the enter key. Unless otherwise you press
the enter key, all positions that you have selected will not be set.

17

LC-20B4M

TROUBLE SHOOTING TABLE

No or Wrong
Picture

Does the IC801
test pattern appear
properly?

Yes

Check the IC801 signal
output line, IC801 itself
and its peripheral
circuits.

Are the waveforms at the signal
input pins of IC801 as specified?
TV/Composite Pin (73)
S Video Pins (72) and (73)
Component Pins (1), (2), (3)
and (75)

Yes

No

Does the IC1201 test
pattern appear
properly?

Yes

Check IC1201 and its
peripheral circuits as
well as the LCD panel
voltage and waveform.

Are the waveforms at
pins (8), (9), (26), and
(27) of IC1201
as specified?

Yes

No

No

No

Check the related lines,
IC801 itself and its
peripheral circuits.

Check IC801 and its
peripheral circuits.

Check the IC801 signal
input line.

18

TROUBLE SHOOTING TABLE (Continued)

Check all the settings on the microprocessor

’s adjust process menu.

Are inputs

and outputs

of IC801 as

specified?

Does the DPS

test pattern

appear?

Does the

video decoder

test pattern

appear?

Check IC3401

and its

peripheral

parts.

Check

IC1201, its

peripheral

circuits and

the LCD

panel.

Check IC801

and its

peripheral

circuits.

Are inputs

and outputs

of IC3401 as

specified?

Check

IC3401 and

its peripheral

parts.

Is input at Pin

(73) of IC801

as specified?

Check IC801,

AV1 line and

their

peripheral

parts.

Are inputs and

outputs of

Q1602, Q1604

and Q1606 as

specified?

Check Q1602,

Q1604, Q1606

and its

peripheral

parts.

Is output at

pins (57)~(59)

of IC1601

normal?

Check the R,

G and B line.

Is input at

pin (21) of

IC1601

normal?

Check V2V0

line and its

peripheral

parts.

Check IC1601

and its

peripheral

parts.

Are inputs at

Pins (71) and

(72) of IC801

as specified?

Check

SC3405, SY

line, SC line

and peripheral

parts.

Is input at

Pins (4), (5),

(6) and (75)

of IC801 as

specified?

Check J3404,

DVD-Y line,

PB line, PR

line and

peripheral

parts.

Are voltages

at Pins (6),

(7) and (9) of

tuner as

specified?

Check the

power line.

Is output at

Pin (19) of

tuner as

specified?

Check the

tuner and its

peripheral

parts.

Is input at Pin

(16) of

IC3401 as

specified?

Check the

line in

question.

Check IC3401

and its

peripheral

parts.

Are Pins (3)

of IC3401 at

H?

Are Pins (48)

of IC2001 at

H?

Check the

line in

question.

No picture

No picture

at all

No VIDEO

1 or 2

output

No TELE

TEXT

output

No S

VIDEO

output

No

COMPONENT

output

No TV

output

Yes

No

Yes

No

No

No

Yes

No

No

Yes

Yes

No

No

Yes

No

No

Yes

No

Yes

No

No

Yes

Yes

No

Yes

LC-20B4M

19

LC-20B4M

Do F3701 and F3702

function?

Check all the settings on the microprocessor

’s adjust process menu.

Are secondary outputs

(+38V, +9V, +5V, -11V) of

T3701 as specified?

Are the oscillation waveform

at T3701’s primary side as

specified?

Disconnect F3701 and

F3702. Is the load side

short-circuited?

Is any of T3701

’s primary

side, Q3703 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 T3701.

Do F6700, F6701,

F6702, F6703, and

F6704 function?

Is Pin (120) of IC1201 at

“H”?

Are the oscillation waveforms

at the primary side of T6700,

T6702, T6704, T6706, and

T6708 as specified?

Replace F6700, F6701,

F6702, F6703, and F6704.

Check the line, IC1201 and

its peripheral parts.

Check Q6700 - 6714, T6700

- 6709 and their peripheral

parts.

Replace the fluorescent lamp

and check the oscillation

waveform again.

Is input at Pin (72) of IC801

as specified?

Check SC3405, SC line and

peripheral parts.

Check all the settings on the microprocessor

’s adjust process menu.

Is input at Pins (1) and (3) of

IC801 as specified?

Check J3404, PB line, PR line

and peripheral parts.

No picture and sound

Yes

No

No

Yes

Yes

No

Yes

No

Fluorescent lamp failure

Yes

No

Yes

No

Yes

No

Yes

Yes

No colour

No TV colour No S-VIDEO colourNo VIDEO colour No COMPONENT colour

No No

TROUBLE SHOOTING TABLE (Continued)

20

TROUBLE SHOOTING TABLE (Continued)

Is Pin (53) of

IC2001 at “L”?

Check all the settings on the microprocessor

’s adjust process menu.

Are outputs at

Pins (1) and (7)

of IC3301/

IC3303 as

specified?

Are inputs at

Pins (2) and (4)

as well as

outputs at Pins

(8) and (12), all

of IC3305, as

specified?

Muting effect is

on. Check the

FSMUTE line.

Check IC3301,

IC3303 and

their peripheral

parts.

Are input and

output of

IC3304 as

specified?

Check IC3304

and its

peripheral parts.

Check the line

in question,

IC3301 and its

peripheral

parts.

Check the

speakers and

their peripheral

parts.

Is Pin (55) of

IC2001 at “L”?

Check the

headphone and

its peripheral

parts.

Check Q2004,

J3303 harness

and their

peripheral parts.

Is Pin (58) of

IC2001 at “L”?

Are outputs at

Pins (14) and

(15) of IC3501

as specified?

Check the line

in question.

Check the

LMUTE line.

Check IC3501,

IC3304 and its

peripheral

parts.

Is output at Pins

(15) and (16) of

tuner as

specified?

Is input at Pin

(67) of IC3304

as specified?

Check IC3304,

X3301 and

their peripheral

parts.

Check the

tuner and its

peripheral

parts.

Check Q3201,

Q3202 and

their peripheral

parts.

No sound

from

speakers

No sound

No sound

from

headphone

No sound

from output

line

TV sound

failure

Yes

No

No

Yes

No

Yes

No

Yes

Yes

No

Yes

No

No

Yes

Yes

No

No

Yes

LC-20B4M

21

LC-20B4M

CHASSIS LAYOUT

H

OPERATION Unit

MAIN Unit

G

F

E

D

C

B

A

TUNER Unit

R/C, LED Unit

22

87109654321

INVERTER-A Unit

LC-20B4M

INVERTER-B Unit

23

1716 1918151413121110

LC-20B4M

C

F
F

F
F

BLOCK DIAGRAM

AGC,AFT,SAW_SW,MODE 1,MODE 2

SC3403

S

H

TV_V

TUNER

TU3201

AV1

INPUT

SIF

V1_V
AV1 _L,R

SIF AMP

Q3201 ,Q3202

G

SY VIDEO

S-VIDEO

INPUT

F

AV2

INPUT/OUTPUT AUDIO IN/OUT VIDEO IN/OUT

COMPONENT

INPUT AUDIO

E

P3501

RXD,TXD

SC SWITCH V_IN

IC3401

AMP

IC3502

V2_V IN/OUT

AV2_L,R IN/OUT V_IN/OUT

SWITCH SWITCH

IC3501,Q3501 Q3502-Q3505

Y,PB,PR

SC1_OUT_R,L

DL,DR

DECODER

L_ERR

AV2_R,L

(MSP)

IC3304

S_IN/OUT

OFL REVERSE

Q3601

OFL

SSTBY

OFL1

D

C

B

A

LAMP

CHECK

PA VCC

DC IN DC/DC 34V

SIG.VCC Q3708 32V

DC13V T3701 9V 9V

INV VCC

PWM

IC3701 -11V -11V

P3601

6LAMPS 4LAMPS

(UP) (DOWN)

P3602

INVERTER A UNIT NVERTER B UNIT

Q6700,Q6701 Q6709, Q6710 RECEIVER
T6700, T6701 T6706, T6707
Q6703, Q6704 Q6712, Q6713
T6702, T6703 T6708, T6709
Q6706, Q6707
T6704, T6705

P3604

AUDIO SOUND
FILTER POWER AMP

IC3301

~

IC3303 IC3305

Q3707 23V

Q3709

5V 5V

IC3702

8V

Q3705 17V

HEADPHONE

JACK

J3303

SP-L

SP-R

87109654321

P3701

P

P35 02P3302P3301P3603

REMOTE

CONTROL

24

LC-20B4M

03

SC2002

FILTER
FL801

FILTER
FL802

I2C

VIDEO

DECODER CONTROLLER

)

(VPC

LCD

(DPS)

IC801 IC1201

REV

V2V0

SYNC SEP IC1101

IC802

R0~7,G0~7,B0~7 PANEL

V0,V7,V21
V64,V112

GRADATION

POWER

V176 ,V235

V255
VCOM
CSCOM

LCD

CSYNC

OSD R/G/B

VLS,VGL,VEE

I2C GSP1,VSH

GBLR,GCK
POWER

E2PROM
MICON
IC2001

RXD,TXD

1

IC2010

RESET

IC2006

TEXT
R/G/B

TEXT R/G/B

AMP

Q1602,Q1604,Q1606

TX_FB

GSP2

P35 02

CONTROL
RECEIVER

P701

Q2002

KEY1
KEY2

POW1 POW2

P2001

SW UNITREMOTE

SWITCH

IC2003

VIDEO SW

IC1604

RX_TX,TX_RX

3.3V REG

3.3V

IC705

3.3V REG

3.3V

IC707

5V REG 5V

IC2004

TELETEXT SRAM 2M

CPU IC1612

IC1601 FLASH 4M

IC1611

25

1716 1918151413121110