JVC LT-37X688, LT-42X688, LT-42X688/C, LT-37X688/V Service Manual

SERVICE MANUAL

YA53520077SERVICE MANUAL

LCD FLAT TELEVISION

LT-37X688/V,
LT-42X688

COPYRIGHT © 2007 Victor Company of Japan, Limited

/C

BASIC CHASSIS

FN2

Illustration of LT-37X688

1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

2 SPECIFIC SERVICE INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18

5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-31

COPYRIGHT © 2007 Victor Company of Japan, Limited

TABLE OF CONTENTS

No.YA535

2007/7

SPECIFICATION

Items

Dimensions ( W × H × D ) 91.9 cm × 65.2 cm × 23 cm

Mass 19.5 kg (42.9 lbs) [Included stand]

Power Input AC120 V , 60 Hz

Power Consumption 210 W (Max) 250 W (Max)

TV RF System
(Analog / Digital)

Color System (Analog) NTSC

Stereo System (Analog) BTSC (Multi Channel Sound)

Teletext System (Analog) Closed caption (T1-T4 / CC1-CC4)

TV Receiving
Channels and
Frequency (Analog)

TV / CATV Total Channel 191 Channels

Intermediate Frequency
(Analog)

Color Sub Carrier Frequency (Analog) 3.58 MHz

LCD panel 37V-inch wide aspect (16:9) 42V-inch wide aspect (16:9)

Screen Size

Display Pixels Horizontal : 1920 dots × Vertical : 1080 dots (W-UXGA)

Audio Power Output 10 W + 10 W

Speaker 4.0 cm × 16.0 cm, twin oblique type × 2

Antenna Terminal
(VHF/UHF, ATSC / DIGITAL CABLE IN)

Digital input
[DIGITAL-IN 1/2]

Video / Audio input
[INPUT-3/4/5]

Audio output (Fix) 500 mV (rms), Low impedance, RCA pin jack × 2
Digital Audio Optical Output Digital SPDIF × 1
Photo Viewer / Service USB connector × 1
Remote Control Unit RM-C1450 (AA/R6 / UM-3 battery × 2)

Component Video

750p / 525p / 525i

VHF Low

VHF High

Video IF

Sound IF

Video / Audio HDMI 2-row 19pin connector × 2

[INPUT-3/4]

S-Video

[INPUT-3]

(36-1/4” x 25-3/4” x 9-1/8”) [Included stand]

91.9 cm × 60.4 cm × 10.8 cm

(36-1/4” x 23-7/8” x 4-3/8”) [TV only]

18.3 kg (40.3 lbs) [TV only]

Analog

CCIR (M)

Digital

ATSC terrestrial / Digital cable

02 ch - 06 ch : 54 MHz - 88 MHz
07 ch - 13 ch : 174 MHz - 216 MHz
14 ch - 69 ch : 470 MHz - 806 MHz

UHF

54 MHz - 804 MHz

CATV

Low Band: 02 - 06
High Band: 07 - 13
Mid Band: 14 - 22
Super Band: 23 - 36
Hyper Band: 37 - 64
Ultra Band: 65 - 94, 100 - 135
Sub Mid Band: 01, 96 - 99

45.75 MHz

41.25 MHz (4.5 MHz)

Diagonal: 94.0 cm (H: 820. cm × V: 46.0 cm)

F-type connector, 75Ω unbalanced, coaxial × 1

(Digital-input terminal is not compatible with picture signals of personal computer)

RCA pin jack × 6

1125i

Y : 1 V (p-p) (Sync signal: 0.35V(p-p), 3-value sync.), 75 Ω
Pb/Pr : ±0.35V(p-p), 75 Ω
Y : 1 V (p-p), Positive (Negative sync.), 75 Ω
Cb/Cr : 0.7V(p-p), 75 Ω

Mini-DIN 4 pin × 1
Y: 1 V (p-p), Positive (Negative sync.), 75 Ω

C: 0.286V (p-p) (Burst signal), 75 Ω
Video 1 V (p-p), Positive (Negative sync.), 75 Ω, RCA pin jack × 3
Audio 500 mV (rms), High impedance, RCA pin jack × 6

LT-37X688 LT-42X688

Contents

103.0 cm × 72.0 cm × 29.6 cm

(40-5/8” x 28-3/8” x 11-3/4”) [Included stand]

103.0 cm × 67.2 cm × 10.8 cm

(40-5/8” x 26-1/2” x 4-3/8”) [TV only]

26 kg (57.2 lbs) [Included stand]

24.1 kg (53.0 lbs) [TV only]

Diagonal: 106.7 cm (H: 93.5 cm × V: 52.8 cm)

Design & specifications are subject to change without notice.

1-2 (No.YA535)

SECTION 1

PRECAUTION

1.1 SAFETY PRECAUTIONS

(1) The design of this product contains special hardware,

many circuits and components specially for safety
purposes. For continued protection, no changes should be
made to the original design unless authorized in writing by
the manufacturer. Replacement parts must be identical to
those used in the original circuits. Service should be
performed by qualified personnel only.

(2) Alterations of the design or circuitry of the products should

not be made. Any design alterations or additions will void
the manufacturer's warranty and will further relieve the
manufacturer of responsibility for personal injury or
property damage resulting therefrom.

(3) Many electrical and mechanical parts in the products 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 these special safety characteristics are identified in
the parts list of Service manual. Electrical components

having such features are identified by shading on the
schematics and by ( ) on the parts list in Service
manual. The use of a substitute replacement which does

not have the same safety characteristics as the
recommended replacement part shown in the parts list of
Service manual may cause shock, fire, or other hazards.

(4) Don't short between the LIVE side ground and

ISOLATED (NEUTRAL) side ground or EARTH side
ground when repairing.

Some model's power circuit is partly different in the GND.
The difference of the GND is shown by the LIVE : ( ) side
GND, the ISOLATED (NEUTRAL) : ( ) side GND and
EARTH : ( ) side GND.
Don't short between the LIVE side GND and ISOLATED
(NEUTRAL) side GND or EARTH side GND and never
measure the LIVE side GND and ISOLATED (NEUTRAL)
side GND or EARTH side GND at the same time with a
measuring apparatus (oscilloscope etc.). If above note will
not be kept, a fuse or any parts will be broken.

(5) When service is required, observe the original lead dress.

Extra precaution should be given to assure correct lead
dress in the high voltage circuit area. Where a short circuit
has occurred, those components that indicate evidence of
overheating should be replaced. Always use the
manufacturer's replacement components.

(6) Isolation Check (Safety for Electrical Shock Hazard)

After re-assembling the product, always perform an
isolation check on the exposed metal parts of the cabinet
(antenna terminals, video/audio input and output terminals,
Control knobs, metal cabinet, screw heads, earphone jack,
control shafts, etc.) to be sure the product is safe to operate
without danger of electrical shock.

a) Dielectric Strength Test

The isolation between the AC primary circuit and all metal
parts exposed to the user, particularly any exposed metal
part having a return path to the chassis should withstand a
voltage of 3000V AC (r.m.s.) for a period of one second. (.
. . . Withstand a voltage of 1100V AC (r.m.s.) to an
appliance rated up to 120V, and 3000V AC (r.m.s.) to an
appliance rated 200V or more, for a period of one second.)
This method of test requires a test equipment not generally
found in the service trade.

b) Leakage Current Check

Plug the AC line cord directly into the AC outlet (do not use
a line isolation transformer during this check.). Using a
"Leakage Current Tester", measure the leakage current
from each exposed metal part of the cabinet, particularly
any exposed metal part having a return path to the chassis,
to a known good earth ground (water pipe, etc.). Any
leakage current must not exceed 0.5mA AC (r.m.s.).
However, in tropical area, this must not exceed 0.2mA AC
(r.m.s.).

Alternate Check Method

Plug the AC line cord directly into the AC outlet (do not
use a line isolation transformer during this check.). Use

an AC voltmeter having 1000Ω per volt or more
sensitivity in the following manner. Connect a 1500Ω
10W resistor paralleled by a 0.15µF AC-type capacitor

between an exposed metal part and a known good earth
ground (water pipe, etc.). Measure the AC voltage
across the resistor with the AC voltmeter. Move the
resistor connection to each exposed metal part,
particularly any exposed metal part having a return path
to the chassis, and measure the AC voltage across the
resistor. Now, reverse the plug in the AC outlet and
repeat each measurement. Any voltage measured must
not exceed 0.75V AC (r.m.s.). This corresponds to

0.5mA AC (r.m.s.).
However, in tropical area, this must not exceed 0.3V AC
(r.m.s.). This corresponds to 0.2mA AC (r.m.s.).

AC VOLTMETER
(HAVING 1000 /V,
OR MORE SENSITIVITY)

0.15 F AC-TYPE

GOOD EARTH GROUND

1500 10W

PLACE THIS PROBE
ON EACH EXPOSED
ME TAL PAR T

(No.YA535)1-3

1.2 INSTALLATION

1.2.1 HEAT DISSIPATION

If the heat dissipation vent behind this unit is blocked, cooling
efficiency may deteriorate and temperature inside the unit will
rise. The temperature sensor that protects the unit will be
activated when internal temperature exceeds the pre-determined
level and power will be turned off automatically.Therefore,
please make sure pay attention not to block the heat dissipation
vent as well as the ventilation outlet behind the unit and ensure
that there is room for ventilation around it.

Ventilation hole

INPUT 1 INPUT 2

75

DIGITAL AUDIO

PHOTO VIEWER /

(VHF/UHF)

OPTICAL OUT

INPUT 3 INPUT 4 INPUT 5

S-VIDEO

Y

VIDEO

Y

COMPONENT

L

P

B

B

P

AUDIO

R

P

R

P

R

AUDIO OUT

VIDEO

VIDEO

COMPONENT

L

L

L

AUDIO

AUDIO

AUDIO

R

R

R

SERVICE

1.2.3 INSTALLATION REQUIREMENTS

To ensure safety in an emergency such as an earthquake, and
to prevent accidents, ensure that measures are taken to prevent
the TV dropping or falling over.

It fixes in a band.

TV STAND

*Diagram differs from actual appearance.

1.2.4 NOTES ON HANDLING

When taking the unit out of a packing case, do not grasp the
upper part of the unit. If you take the unit out while grasping the
upper part, the LCD PANEL may be damaged because of a
pressure. Instead of grasping the upper part, put your hands on
the lower backside or sides of the unit.

*Diagram differs from actual appearance.

1.2.2 INSTALLATION REQUIREMENTS

Ensure that the minimal distance is maintained, as specified
below, between the unit with and the surrounding walls, as well
as the floor etc.Install the unit on stable flooring or stands.Take
precautionary measures to prevent the unit from tipping in order
to protect against accidents and earthquakes.

150 mm

200 mm

POWER

*Diagram differs from actual appearance.

150 mm

200 mm

50 mm

1-4 (No.YA535)

1.3 HANDLING LCD PANEL

1.3.1 PRECAUTIONS FOR TRANSPORTATION

When transporting the unit, pressure exerted on the internal LCD
panel due to improper handling (such as tossing and dropping)
may cause damages even when the unit is carefully packed. To
prevent accidents from occurring during transportation, pay
careful attention before delivery, such as through explaining the
handling instructions to transporters.
Ensure that the following requirements are met during
transportation, as the LCD panel of this unit is made of glass and
therefore fragile:

(1) USE A SPECIAL PACKING CASE FOR THE LCD PANEL

When transporting the LCD panel of the unit, use a special
packing case (packing materials). A special packing case
is used when a LCD panel is supplied as a service spare
part.

(2) ATTACH PROTECTION SHEET TO THE FRONT

Since the front (display part) of the panel is vulnerable,
attach the protection sheet to the front of the LCD panel
before transportation. Protection sheet is used when a LCD
panel is supplied as a service spare part.

(3) AVOID VIBRATIONS AND IMPACTS

The unit may be broken if it is toppled sideways even when
properly packed. Continuous vibration may shift the gap of
the panel, and the unit may not be able to display images
properly. Ensure that the unit is carried by at least 2
persons and pay careful attention not to exert any vibration
or impact on it.

(4) DO NOT PLACE EQUIPMENT HORIZONTALLY

Ensure that it is placed upright and not horizontally during
transportation and storage as the LCD panel is very
vulnerable to lateral impacts and may break. During
transportation, ensure that the unit is loaded along the
traveling direction of the vehicle, and avoid stacking them
on one another. For storage, ensure that they are stacked
in 2 layers or less even when placed upright.

1.3.2 OPTICAL FILTER (ON THE FRONT OF THE LCD PANEL)

(1) Avoid placing the unit under direct sunlight over a

prolonged period of time. This may cause the optical filter
to deteriorate in quality and color.

(2) Clean the filter surface by wiping it softly and lightly with a

soft and lightly fuzz cloth (such as outing flannel).

(3) Do not use solvents such as benzene or thinner to wipe the

filter surface. This may cause the filter to deteriorate in
quality or the coating on the surface to come off. When
cleaning the filter, usually use the neutral detergent diluted
with water. When cleaning the dirty filter, use water-diluted
ethanol.

(4) Since the filter surface is fragile, do not scratch or hit it with

hard materials. Be careful enough not to touch the front
surface, especially when taking the unit out of the packing
case or during transportation.

1.3.3 PRECAUTIONS FOR REPLACEMENT OF EXTERIOR
PARTS

Take note of the following when replacing exterior parts (REAR
COVER, FRONT PANEL, etc.):

(1) Do not exert pressure on the front of the LCD panel (filter

surface). It may cause irregular color.

(2) Pay careful attention not to scratch or stain the front of the

LCD panel (filter surface) with hands.

(3) When replacing exterior parts, the front (LCD panel) should

be placed facing downward. Place a mat, etc. underneath
to avoid causing scratches to the front (filter surface).

(No.YA535)1-5

1.4 TUNER DIAGNOSTIC SCREEN

This model has a function to check the connection status of the
digital tuner. The connection status can be checked following the
below procedure.

(1) Receive digital broadcasting.
(2) Press the [MENU] key to display the user menu.
(3) Select "TUNER SETUP" from the user menu, and then

press the [OK] key.

(4) Select Tuner Diagnostic (Service Use Only) from "TUNER

SETUP", and then press the [OK] key.

(5) The below screen is displayed.

Tuner Diagnostic

Frequency 803000kHz

Modulation NTSC

Input level 0

SR -

RSE -

FO -

Ch# -2

Station

BACK

MENU

Back

Exit

Frequency

This is the in-band frequency tuned up now. If channel map is
not available, this value will be set to 0 or it may become the
frequency tuned up last time.

Modulation

This is the in-band modulation mode now. “NTSC / 64QAM /
256QAM / 8VSB”

Input level

This is the input signal power level of in-band. This value var­ies between 0 and 100.

SR

This is the Signal noise Ratio.

RSE

This is uncorrectable error packet count. (Read-Solomon Error
Correction Processing) When this value is not 0, it may have
influence on the quality of video or audio. However, note that
this value does not display an exact value depending on tim­ing. If a signal is weak, this error will be occurred, but even if a
signal is too strong, it occurs.

FO

This is the out-of-band frequency tuned up now. This value
varies between 70000kHz and 130000kHz. If OOB is received
normally, frequency will be locked to a certain value (this
changes with an area or cable operators). When frequency is
continuing changing, OOB is not normally received.

Ch#

This is the channel number now.

Station

This is the channel station name now.

1-6 (No.YA535)

SECTION 2

SERVICE MENU

1. TV-Micro Service

2. Digital Service

3. Digital Diagnostics

4. Digital Engineering Functions

TV-Micro Service

1. ADJUST

2. SELF CHECK

3. I2C STOP

LOB 0 FAN 0
AUD 0

ANA 9 DIG 9

0000 0
0

SPECIFIC SERVICE INSTRUCTIONS

2.1 SYSTEM SETTEING

Be sure to carry out the following operation at the end of
the procedure.

(1) Set to "0 minutes" using the [SLEEP] key.
(2) While "0 minutes" is displayed, press the [VIDEO] key and

[DISPLAY] key simultaneously, then enter the SERVICE

MODE.
(3 ) Press the [1] key in the SERVICE MODE SCREEN. (Fig.1)
(4) Press the [2] key in the TV-MICRO SERVICE MODE

screen. (Fig.2)
(5) The SELF CHECK MODE screen is displayed. (Fig.3)
(6) Turn off the power by pressing the [POWER] key on the

remote control unit.

SERVICE MODE SCREEN

SERVICE MENU

1. TV-Micro Service

2. Digital Service

3. Digital Diagnostics

4. Digital Engineering Functions

TV-MICRO SERVICE MODE SCREEN

Fig.1

Press [1] key

2.2 FEATURES

Built in ATSC (Advanced Television Systems Committee)
TUNER

This TV can receive both Digital broadcasting (ATSC) and
Analog broadcasting.

D.I.S.T. (Digital Image Scaling Technology)

This system uses line interpolation to double the number of
scanning lines and achieve high resolution, flicker-free picture.

Color Management

This function ensures dull colors are compensated to produce
natural hues.

Picture Management

This function makes it easier to see the dark areas when a
picture has many dark areas, and makes it easier to see the
bright areas when a picture has many bright areas.

Smart Picture

This function detects the APL (Average Picture Level) and
adjusts the contrast suitable for what you are watching.

DIGITAL VNR

This function cuts down the amount of noise in the original
picture.

MPEG Noise Reduction

This function effects the block noise removal and mosquito NR
simultaneously.

Sensor Effect

With Sensor Effect ON, a "leaf" icon will appear on your TV
screen when Smart Sensor brightness adjustment occurs.

SELF CHECK MODE(TV-MICRO)

TV-Micro Service

1. ADJUST

2. SELF CHECK

3. I2C STOP

Fig.2

LOB 0 FAN 0
AUD 0

ANA 9 DIG 9

0000 0
0

Fig.3

Press [2] key

SCREEN

(No.YA535)1-7

2.3 TECHNICAL INFORMATION

2.3.1 LCD PANEL

This unit uses the flat type panel LCD (Liquid Crystal Display) panel that occupies as little space as possible, instead of the
conventional CRT (Cathode Ray Tube), as a display unit.
Since the unit has the two polarizing filter that are at right angles to each other, the unit adopts "normally black" mode, where light
does not pass through the polarizing filter and the screen is black when no voltage is applied to the liquid crystals.

2.3.1.1 SPECIFICATIONS

The following table shows the specifications of this unit.

Item

LT-37X688 LT-42X688

Specifications

Maximum dimensions ( W × H × D ) 87.7 cm × 51.5 cm × 5.4 cm 98.3 cm × 57.6 cm × 5.2 cm

Weight 11.0 kg 13.0 kg

Effective screen size Diagonal: 94.0 cm (H: 81.9 cm × V: 46.0 cm) Diagonal: 107.3 cm (H: 93.0 cm × V: 52.3 cm)

Aspect ratio 16 : 9

Drive device / system a-Si-TFT active matrix system

Resolution Horizontally 1920 × Vertically 1080 × RGB < W-XGA > 6220800 dots in total

Pixel pitch (pixel size)

Horizontally: 0.42675 mm, Vertically: 0.42675 mm Horizontally: 0.1615 mm, Vertically: 0.4845 mm

Displayed colour 16777216 colours 256 colours for R G and B

Brightness 500 cd/m

2

Contrast ratio 1200 : 1 1500 : 1

Response time 6 ms 6.5 ms

View angle Horizontally: 176°, Vertically: 176°

Surface polarizer Anti-Glare type Low reflective coat

Colour filter Vertical stripe

Backlight Cold cathode fluorescent lamp × 20

Power supply voltage in LCD 12 V

Power supply voltage in inverter 24 V

Panel interface system LVDS (Low Voltage Differential Signaling)

2.3.1.2 PIXEL FAULT

There are three pixel faults - bright fault, dark fault and flicker fault - that are respectively defined as follows.

 BRIGHT FAULT

In this pixel fault, a cell that should not light originally is lighting on and off.
For checking this pixel fault, input ALL BLACK SCREEN and find out the cell that is lighting on and off.

 DARK FAULT

In this pixel fault, a cell that should light originally is not lighting or lighting with the brightness twice as brighter as originally lighting.
For checking this pixel fault, input 100% of each R/G/B color and find out the cell that is not lighting.

 FLICKER FAULT

In the pixel fault, a cell that should light originally or not light originally is flashing on and off.
For checking this pixel fault, input ALL BLACK SCREEN signal or 100% of each RGB color and find out the cell that is flashing on
and off.

1-8 (No.YA535)

2.3.2 MAIN CPU PIN FUNCTION [IC7001

Pin Pin name I/O Function Pin Pin name I/O Function

1 VHOLD1 I Not used: Data slice for main screen closed caption 51 NC O Not used

2 HFLT1 I/O

3 NC O Not used 53 NC O Not used

4 NC O Not used 54 NC O Not used

5 DIGR0 O R [0] for OSD 55 NC O Not used

6 TB1in I AC power for timer clock 56 NC O Not used

7 REMO I Remote control 57 NC O Not used

8 BYTE I Data bus width select [L = 16bit (fixed)] 58 NC O Not used

9 CNVss I CPU programming mode select [Normal = L] 59 NC O Not used

10 DIGG0 O G [0] for OSD 60 NC O Not used

11 DIGB0 O B [0] for OSD 61 NC O Not used

12 RESET I Reset for main CPU [Reset = L] 62 HSYNC I H. sync for OSD

13 Xout O System clock osillation (crystal) : 16MHz 63 NC O Not used

14 Vss - GND 64 VSYNC I V. sync for OSD

15 Xin I System clock osillation (crystal) : 16MHz 65 NC O Not used

16 VccI I 3.3V stand-by power supply 66 NC O Not used

17 OSC1 I Clock for OSD 67 NC O Not used

18 OSC2 O Not used : Clock for OSD 68 NC O Not used

19 INT1 I Not used: AV COMPULINK control 69 NC O Not used

20 INT0 I

21 OUT1 O Ys (blanking) for OSD 71 P2.1 O Not used: Clock for Inter IC (serial) bus control

22 OUT2 O YM (transparence) for OSD 72 P2.0 I/O Not used: Data for Inter IC (serial) bus control

23 NC O Not used 73 NC O Not used

24 NC O Not used 74 NC O Not used

25 NC O Not used 75 NC O Not used

26 NC O Not used 76 NC O Not used

27 CTA2/RTS2 O Not used 77 NC O Not used

28 CLK2 O Not used 78 NC O Not used

29 RxD2 I Not used: Digital tuner control 79 NC O Not used

30 TxD2 O Not used: Digital tuner control 80 P1.0 I main CPU update

31 SDA2 I/O Not used 81 P0.7 O Not used

32 DIGR1 O R [1] for OSD 82 P0.6 O Not used

33 DIGG1 O G [1] for OSD 83 CEC_INT O Not used

34 DIGB1 O B [1] for OSD 84 WAKE O

35 TxD0 I Data transmission (serial) for external programming 85 CARD_DET I Not used

36 RxD0 O Data receive (serial) for external programming 86

37 CLK0 I Clock for external programming 87 SDA I/O Data for Inter IC (serial) bus control : memory

38 RTS0 O Busy for external programming [Operation = H] 88 SLC O Clock for Inter IC (serial) bus control : memory

39 P5.7 I Not used 89 DIGR2 O R [2] for OSD

40 P5.6 O Not used 90 DIGG2 O G [2] for OSD

41 HOLD I CPU programming mode select [Normal = H] 91 DIGB2 O B [2] for OSD

42 P5.4 O Not used 92 NC O Not used

43 P5.3 O Not used 93 KEY2 I

44 P5.2 O Not used 94 KEY1 I

45 P5.1 O Not used 95 VHOLD2 I Not used: Data slice for sub screen closed caption

46 WR O CPU programming mode select [Normal = H] 96 HLF2 I/O

47 P4.7 O

48 P4.6 I

49 P4.5 O Clock for sub(chassis) CPU communication (serial) 99 VCCE I 5V stand-by power supply

50 P4.4 O Not used 100 CVIN1 I Not used: Video(Y) for main screen closed caption

Not used: LPF for main screen closed caption video input

Interrupt request for sub(chassis) CPU [Request = L]

Data transmission for sub(chassis) CPU communication (serial)

Data receive for sub(chassis) CPU communication (serial)

: DIGITAL PWB ASS'Y]

52 NC O Not used

70 NC O Not used

Release of low power mode for sub(chassis) CPU [Release = L]

POWER_SW

97 CVIN2 I Not used: Video(Y) for sub screen closed caption

98 TVSETB I Test terminal [L Fixed]

I Power switch (mechanical) detection [On = L]

Key scan data for side control button (MENU/CH+/CH-) KEY2

Key scan data for side control button (INPUT/VOL+/VOL-) KEY1

Not used: LPF for sub screen closed caption video input

(No.YA535)1-9

SECTION 3

DISASSEMBLY

3.1 CAUTION AT DISASSEMBLY

• Be sure to perform the SYSTEM SETTEING, at the end of the procedure.

• Make sure that the power cord is disconnected from the outlet.

• Pay special attention not to break or damage the parts.

• Make sure that there is no bent or stain on the connectors before inserting, and firmly insert the connectors.

REFERENCE:

When removing each board, remove the connector if necessary. The operation is easier if you write down the connection points
(connector numbers) of the connector. For connection of each board, refer to the "WIRING DIAGRAM" of the Standard Circuit
Diagram.

3.2 DISASSEMBLY PROCEDURE [LT-37X688/V]

3.2.1 REMOVING THE REAR COVER (Fig.3-1)

(1) Remove the 1 screw [A].
(2) Remove the CORD CLAMP.
(3) Remove the 10 screws [B], the 3 screws [C], and the 7

screws [D].

(4) Remove the REAR COVER.

3.2.6 REMOVING THE SW PWB (Fig.3-1)

• Remove the REAR COVER.
(1) Remove the 2 screws [M].
(2) Remove the SW PWB.
(3) Remove the 2 screws [N].
(4) Remove the CONTROL KNOB.

3.2.2 REMOVING THE STAND ASS’Y (Fig.3-1)

• Remove the CORD CLAMP
(1) Remove the 4 screws [E].
(2) Remove the STAND ASS’Y in the direction of the arrow.

3.2.3 REMOVING THE POWER PWB (Fig.3-1)

• Remove the REAR COVER.
(1) Remove the 1 screw [F].
(2) Remove the POWER CORD HOLDER.
(3) Remove the POWER CORD.
(4) Remove the 10 screws [G].
(5) Remove the POWER PWB.

3.2.4 REMOVING THE ANALOG PWB (Fig.3-1)

• Remove the REAR COVER.
(1) Remove the 6 screws [H].
(2) Remove the ANALOG PWB.

3.2.5 REMOVING THE DIGITAL PWB (Fig.3-1)

• Remove the REAR COVER.
(1) Remove the 1 screw [J].
(2) Remove the DIGITAL BASE.
(3) Remove the SHIELD COVER.
(4) Remove the 5 screws [K].
(5) Remove the DIGITAL PWB.
(6) Remove the 4 screws [L].
(7) Remove the SHIELD BASE.

CAUTION:

Make sure to perform the "SYSTEM SETTEING", when
DIGITAL PWB is replaced.

3.2.7 REMOVING THE LED PWB (Fig.3-1)

• Remove the REAR COVER.

• Remove the STAND ASS’Y.
(1) Remove the 2 screw [P].
(2) Remove the STAND BASE COVER.
(3) Remove the 2 screws [Q] and 3 screws [R].
(4) Remove the STAND BASE SUPPORT.
(5) Remove the 2 hooks [a] and 1 screw [S].
(6) Remove the LED PWB.

3.2.8 REMOVING THE SPEAKER (Fig.3-1)

• Remove the REAR COVER.

• Remove the STAND ASS’Y.

• Remove the STAND BASE COVER.

• Remove the STAND BASE SUPPORT.
(1) Remove the 3 screws [T].
(2) Remove the SPEKAER.
(3) Follow the same steps when removing the other hand

SPEAKER.

NOTE

When the SPEAKER is decomposed, the performance cannot
be kept.

3.2.9 REMOVING THE LCD PANEL UNIT (Fig.3-1)

• Remove the REAR COVER.

• Remove the STAND ASS’Y.

• Remove the STAND BASE COVER.

• Remove the STAND BASE.

• Remove the SPEKAER.
(1) Remove the 5 screws [U] and 4 screws [V].
(2) Remove the MAIN BASE.
(3) Remove the 4 screws [W].
(4) Remove the SUPPORT BRACKET.
(5) Remove the LCD PANEL UNIT from the FRONT PANEL.

1-10 (No.YA535)

D

D

D

C

B

B

MAIN POWER PWB

G

U

POWER CORD

F

H

U

V

POWER CORD
HOLDER

ANALOG PWB

U

MAIN BASE

C

REAR COVER

U

V

DIGITAL BASE

J

B

A

CORD CLAMP

SHIELD COVER

DIGITAL PWB

P

E

STAND BASE COVER

K

L

SHIELD BASE

U

STAND ASS'Y

U

R

Q

R

STAND BASE SUPPORT

S

LED PWB

LCD PANEL UNIT

SUPPORT BRACKET

CONTROL SW PWB

M

N

N

CONTROL KNOB

Fig.3-1

W

W

SUPPORT BRACKET

FRONT PANEL

T

T

T

a

SPEAKER

T

SPEAKER

(No.YA535)1-11