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SERVICE MANUAL
LCD PANEL TELEVISION
8
2005
YA235
LT-20E50SJ,
LT-20E50SU,
LT-20E50SU/Z
DVD
TV
VCR
MENU
BACK
P
PC
TV
TABLE OF CONTENTS
1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 SPECIFIC SERVICE INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
COPYRIGHT © 2005 Victor Company of Japan, Limited No.YA235
2005/8
SPECIFICATION
Items Contents
Dimensions ( W × H × D ) 61.7cm × 43.0cm × 23.5cm [Included stand]
61.7cm × 39.6cm × 7.3cm [TV only]
Mass 8.6kg [Included stand]
7.0kg [TV only]
Power Input AC100V to AC240 V, 50 Hz
Power Consumption 54W (Standby: 3.0W)
TV RF System CCIR B/G, I, D/K, L
Colour System PAL / SECAM / NTSC 3.58 / NTSC 4.43 (NTSC: EXT only).
Stereo System A2 (B/G, D/K), NICAM (B/G, I, D/K, L)
Teletext System FLOF (Fastext), TOP, WST (World Standard System)
Receiving Frequency VHF 47MHz to 470MHz
UHF 470MHz to 862MHz
CATV 116MHz to 172MHz / 220MHz to 469MHz
Intermediate Frequency VIF 38.9MHz(B/G, D/K, I)
SIF 33.4MHz(5.5MHz:B/G) / 32.9MHz(6.0MHz:I) / 32.4MHz(6.5MHz:L,D/K)
Colour Sub Carrier PAL 4.43MHz
Frequency SECAM 4.40625MHz / 4.25MHz
NTSC 3.58MHz / 4.43MHz
LCD Panel 20V-inch
Screen Size Diagonal : 51.1cm (H:41.1cm × V : 30.9cm)
Display Pixels Horizontal : 800 dots × Vertical : 600 dots (SVGA)
Audio Power Output 5W + 5W(10% THD)
Speaker 5.0cm, oval type × 2
Aerial Terminal (VHF/UHF) 75 unbalanced, coaxial
EXT-1 / EXT-2 (Input / Output) 21-pin Euro connector (SCART socket ) × 2
EXT-3(Input) Component Video RCA pin jack × 3
625p / 525p / 625i / 525i Y : 1V (p-p), Positive (Negative sync provided), 75
Cb/Cr : 0.7V(p-p), 75
Audio 500mV(rms) (-4dBs), high impedance, RCA pin jack × 2
EXT-4 (Input) S-Video Mini-DIN 4 pin × 1
Y: 1V (p-p), Positive (Negative sync provided), 75
C: 0.286V (p-p) (Burst signal), 75
Video 1V (p-p), Positive (Negative sync provided), 75 , RCA pin jack × 1
Audio 500mV (rms), High impedance, RCA pin jack × 2
PC (RGB) Input D-sub 15pin × 1
R/G/B : 0.7V (p-p), 75
HD / VD : 1V (p-p) to 5V (p-p), high impedance
< Available signal >
VGA : 640 pixels × 480 pixels (Horizontal : 31.5kHz / Vertical : 60Hz)
XGA : 1024 pixels × 768 pixels (Horizontal : 48.4kHz / Vertical : 60Hz)
PC AUDIO Input 3.5mm stereo mini jack × 1
Audio Output 500mV (rms), Low impedance, RCA pin jack × 2
Subwoofer Output More than 0 to 1000mV (rms) (+2.2dBs), low impedance (80Hz when modulated
100%), RCA pin jack × 1
Headphone 3.5mm stereo mini jack × 1
Remote Control Unit RM-C1860 (AA/R6 dry cell battery × 2)
Design & specifications are subject to change without notice.
1-2 (No.YA235)
SECTION 1
PRECAUTION
1.1 SAFETY PRECAUTIONS
(1) The design of this product contains special hardware, (6) Isolation Check (Safety for Electrical Shock Hazard)
many circuits and components specially for safety After re-assembling the product, always perform an
purposes. For continued protection, no changes should be isolation check on the exposed metal parts of the cabinet
made to the original design unless authorized in writing by (antenna terminals, video/audio input and output terminals,
the manufacturer. Replacement parts must be identical to Control knobs, metal cabinet, screw heads, earphone jack,
those used in the original circuits. Service should be control shafts, etc.) to be sure the product is safe to operate
performed by qualified personnel only. without danger of electrical shock.
(2) Alterations of the design or circuitry of the products should a) Dielectric Strength Test
not be made. Any design alterations or additions will void The isolation between the AC primary circuit and all metal
the manufacturer's warranty and will further relieve the parts exposed to the user, particularly any exposed metal
manufacturer of responsibility for personal injury or part having a return path to the chassis should withstand a
property damage resulting therefrom. voltage of 3000V AC (r.m.s.) for a period of one second. (.
(3) Many electrical and mechanical parts in the products have . . . Withstand a voltage of 1100V AC (r.m.s.) to an
special safety-related characteristics. These appliance rated up to 120V, and 3000V AC (r.m.s.) to an
characteristics are often not evident from visual inspection appliance rated 200V or more, for a period of one second.)
nor can the protection afforded by them necessarily be This method of test requires a test equipment not generally
obtained by using replacement components rated for found in the service trade.
higher voltage, wattage, etc. Replacement parts which b) Leakage Current Check
have these special safety characteristics are identified in Plug the AC line cord directly into the AC outlet (do not use
the parts list of Service manual. Electrical components a line isolation transformer during this check.). Using a
having such features are identified by shading on the "Leakage Current Tester", measure the leakage current
schematics and by ( ) on the parts list in Service from each exposed metal part of the cabinet, particularly
manual. The use of a substitute replacement which does any exposed metal part having a return path to the chassis,
not have the same safety characteristics as the to a known good earth ground (water pipe, etc.). Any
recommended replacement part shown in the parts list of leakage current must not exceed 0.5mA AC (r.m.s.).
Service manual may cause shock, fire, or other hazards. However, in tropical area, this must not exceed 0.2mA AC
(4) Don't short between the LIVE side ground and (r.m.s.).
ISOLATED (NEUTRAL) side ground or EARTH side Alternate Check Method
ground when repairing. Plug the AC line cord directly into the AC outlet (do not
Some model's power circuit is partly different in the GND. use a line isolation transformer during this check.). Use
The difference of the GND is shown by the LIVE : ( ) side an AC voltmeter having 1000 per volt or more
GND, the ISOLATED (NEUTRAL) : ( ) side GND and sensitivity in the following manner. Connect a 1500
EARTH : ( ) side GND. 10W resistor paralleled by a 0.15µF AC-type capacitor
Don't short between the LIVE side GND and ISOLATED between an exposed metal part and a known good earth
(NEUTRAL) side GND or EARTH side GND and never ground (water pipe, etc.). Measure the AC voltage
measure the LIVE side GND and ISOLATED (NEUTRAL) across the resistor with the AC voltmeter. Move the
side GND or EARTH side GND at the same time with a resistor connection to each exposed metal part,
measuring apparatus (oscilloscope etc.). If above note will particularly any exposed metal part having a return path
not be kept, a fuse or any parts will be broken. to the chassis, and measure the AC voltage across the
(5) When service is required, observe the original lead dress. resistor. Now, reverse the plug in the AC outlet and
Extra precaution should be given to assure correct lead repeat each measurement. Any voltage measured must
dress in the high voltage circuit area. Where a short circuit not exceed 0.75V AC (r.m.s.). This corresponds to
has occurred, those components that indicate evidence of 0.5mA AC (r.m.s.).
overheating should be replaced. Always use the However, in tropical area, this must not exceed 0.3V AC
manufacturer's replacement components. (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
PLACE THIS PROBE
ON EACH EXPOSED
1500 10W METAL PART
GOOD EARTH GROUND
(No.YA235)1-3
1.2 INSTALLATION
1.2.1 HEAT DISSIPATION 1.2.3 INSTALLATION REQUIREMENTS
If the heat dissipation vent behind this unit is blocked, cooling To ensure safety in an emergency such as an earthquake, and
efficiency may deteriorate and temperature inside the unit will to prevent accidents, ensure that measures are taken to prevent
rise. The temperature sensor that protects the unit will be the TV dropping or falling over.
activated when internal temperature exceeds the pre-determined Use the supplied screws to firmly attach the supplied hooks
level and power will be turned off automatically.Therefore, (OPTION) to the back of the TV, and use commercially available
please make sure pay attention not to block the heat dissipation cord to fix the TV to rigid components such as walls and columns.
vent as well as the ventilation outlet behind the unit and ensure
that there is room for ventilation around it. Wall
Hook
Ventilation hole
*Diagram differs from actual appearance.
1.2.2 INSTALLATION REQUIREMENTS
Ensure that the minimal distance is maintained, as specified TV Stand
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 It fixes in a band.
to protect against accidents and earthquakes. *Diagram differs from actual appearance.
1.2.4 NOTES ON HANDLING
(1) WHEN TAKING UNIT OUT OF A PACKING CASE
100 mm 100 mm 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
100 mm 100 mm
50 mm because of a pressure. Instead of grasping the upper part,
put your hands on the lower backside or sides of the unit.
TV / AV
MENU
P/ch
(2) AS FOR PRESSING OR TOUCHING A SPEAKER
Be careful not to press the opening of the speaker in the
lower part of the unit and around them since the decorative
sheet on the surface of the openings may be deformed.
*Diagram differs from actual appearance.
1-4 (No.YA235)
1.3 HANDLING LCD PANEL
1.3.1 PRECAUTIONS FOR TRANSPORTATION 1.3.2 OPTICAL FILTER (ON THE FRONT OF THE LCD PANEL)
When transporting the unit, pressure exerted on the internal LCD (1) Avoid placing the unit under direct sunlight over a
panel due to improper handling (such as tossing and dropping) prolonged period of time. This may cause the optical filter
may cause damages even when the unit is carefully packed. To to deteriorate in quality and COLOUR.
prevent accidents from occurring during transportation, pay (2) Clean the filter surface by wiping it softly and lightly with a
careful attention before delivery, such as through explaining the soft and lightly fuzz cloth (such as outing flannel).
handling instructions to transporters. (3) Do not use solvents such as benzene or thinner to wipe the
Ensure that the following requirements are met during filter surface. This may cause the filter to deteriorate in
transportation, as the LCD panel of this unit is made of glass and quality or the coating on the surface to come off. When
therefore fragile: cleaning the filter, usually use the neutral detergent diluted
(1) USE A SPECIAL PACKING CASE FOR THE LCD PANEL with water. When cleaning the dirty filter, use water-diluted
When transporting the LCD panel of the unit, use a special ethanol.
packing case (packing materials). A special packing case (4) Since the filter surface is fragile, do not scratch or hit it with
is used when a LCD panel is supplied as a service spare hard materials. Be careful enough not to touch the front
part. surface, especially when taking the unit out of the packing
(2) ATTACH PROTECTION SHEET TO THE FRONT case or during transportation.
Since the front (display part) of the panel is vulnerable,
attach the protection sheet to the front of the LCD panel 1.3.3 PRECAUTIONS FOR REPLACEMENT OF EXTERIOR
before transportation. Protection sheet is used when a LCD PARTS
panel is supplied as a service spare part. Take note of the following when replacing exterior parts (REAR
(3) AVOID VIBRATIONS AND IMPACTS COVER, FRONT PANEL, etc.):
The unit may be broken if it is toppled sideways even when (1) Do not exert pressure on the front of the LCD panel (filter
properly packed. Continuous vibration may shift the gap of surface). It may cause irregular COLOUR.
the panel, and the unit may not be able to display images (2) Pay careful attention not to scratch or stain the front of the
properly. Ensure that the unit is carried by at least 2 LCD panel (filter surface) with hands.
persons and pay careful attention not to exert any vibration (3) When replacing exterior parts, the front (LCD panel) should
or impact on it. be placed facing downward. Place a mat, etc. underneath
(4) DO NOT PLACE EQUIPMENT HORIZONTALLY to avoid causing scratches to the front (filter surface).
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.
(No.YA235)1-5
SECTION 2
SPECIFIC SERVICE INSTRUCTIONS
2.1 FEATURES
T-V LINK OFF TIMER
When you have a T-V LINK compatible VCR connected to the This function can set the TV to automatically turn off after a set
EXT-2 Terminal on the TV,it is easier to set up the VCR and to time.
view videos. COLOUR SYSTEM
ZOOM If the picture is not clear or no colour appears, change the
This function can change the screen size according to the current colour system to another colour system.
picture aspect ratio.
2.2 MAIN DIFFERENCE LIST
Items LT-20E50SJ LT-20E50SU LT-20E50SU/Z
POWER CORD UK type(3-pin ) EU type(2-pin ) SWE Type(3-pin )
2.3 21-PIN EURO CONNECTOR (SCART) : EXT-1 / EXT-2
Pin No. Signal designation Matching value EXT-1 EXT-2
1 AUDIO R output 500mV(rms) (Nominal),, Low impedance Used (TV OUT) Used (LINE OUT)
2 AUDIO R input 500mV(rms) (Nominal),, High impedance Used (R1) Used (R2)
3 AUDIO L output 500mV(rms) (Nominal),, Low impedance Used (TV OUT) Used (LINE OUT)
4 AUDIO GND Used Used
5 GND (B) Used Used
6 AUDIO L input 500mV(rms) (Nominal),, High impedance Used (L1) Used (L2)
7 B input 700mV(B-W), 75 Used Used
8 FUNCTION SW Low : 0V-3V Used Used
(SLOW SW) High : 8V-12V, High impedance
9 GND (G) Used Used
10 SCL / T-V LINK Not used Used
(SCL2 / TV-LINK)
11 G input 700mV(B-W), 75 Used Used
12 SDA Not used Used (SDA2)
13 GND (R) Used Used
14 GND (YS) Used Not used
15 R / C input R : 700mV(B-W), 75 Used (R) Used (C2/R)
C : 300mV(P-P), 75
16 Ys input (FAST SW) Low : 0V-0.4V, High : 1V-3V, 75 Used Used
17 GND (VIDEO output) Used Used
18 GND (VIDEO input) Used Used
19 VIDEO output 1V(P-P) (Negative sync), 75 Used (TV OUT) Used (LINE OUT)
20 VIDEO / Y input 1V(P-P) (Negative sync), 75 Used Used
21 COMMON GND Used Used
(P-P= Peak to Peak, B-W= Blanking to white peak)
[Pin assignment]
20 18 16 14 12 10 8 6 4 2
21 19 17 15 13 11 9 7 5 3 1
1-6 (No.YA235)
2.4 TECHNICAL INFORMATION
2.4.1 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.
2.4.1.1 SPECIFICATIONS
The following table shows the specifications of this unit.
Item Specifications Remarks
Displayed colour 16777216 colours 256 colours for R, G, and B
Brightness 500cd/m2
Contrast ratio 500: 1
Response time 16ms
View angle Horizontally: 160°, Vertically: 120°
2.4.1.2 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 colour 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 colour and find out the cell that is flashing on
and off.
(No.YA235)1-7
2.5 BASIC OPERATION OF SERVICE MODE 2.5.5 SERVICE MODE SETTING ITEMS
2.5.1 HOW TO ENTER THE SERVICE MODE Setting
Setting items Contents
(1) Press [INFORMATION] key and [MUTING] key on the menu
remote control unit simultaneously to enter the SERVICE Adjust Group ----
MODE SCREEN. Mode ----
Col. Temp. ----
Contrast ----
SERVICE MODE SCREEN Brightness ----
Colour ----
Sharpness ----
Red ----
Service
Green ----
Adjust ... Blue ----
Options ... Aps Volume ----
Aps Wss Test ...
Option 1 First APS If ON, TV starts with APS
17JVC 0. 0. 86
menu at Start-up
Sep 27 2004 08:47:10
BG ----
DK ----
I ----
L ----
L' ----
FM Prs Avl On Adjusts the FM Prescaler
value, when Automatic
2.5.2 HOW TO EXIT THE SERVICE MODE Volume Levelling is On
Press the [MENU] key to exit the Service mode. Nicam Prs Avl On Adjusts the Nicam Prescal-
er value, when Automatic
2.5.3 CHANGE AND MEMORY OF SETTING VALUE Volume Levelling is On
SELECTION OF SETTING MENU & ITEM Scart Prs Avl On Adjusts the Scart Volume
· [FUNCTION / ] key : Select the SETTING MENU & ITEM value, when Automatic
· [OK] key : Decision the SETTING MENU & ITEM Volume Levelling is On
Scart Volume Avl On Adjusts the Scart Volume
CHANGE OF SETTING VALUE (DATA) value, when Automatic
· [FUNCTION / ] key. Volume Levelling is On
FM Prs Avl Off Adjusts the FM Prescaler
MEMORY OF SETTING VALUE (DATA) value, when Automatic
The setting value will be stored automatically when release the Volume Levelling is Off
REMOTE CONTROL UNIT keys Option 2 Nicam Prs Avl Off Adjusts the Nicam Prescal-
er value, when Automatic
2.5.4 SERVICE MODE SELECT KEY LOCATION Volume Levelling is Off
Scart Prs Avl Off Adjusts the Scart Prescal-
er value, when Automatic
Volume Levelling is Off
Scart Volume Avl Off Adjusts the Scart Volume
value, when Automatic
Volume Levelling is On
Avl Enable/disable Automatic
Volume Levelling System
Sound ----
Carrier ----
[OK] LDLY ----
[ ] [ ] AGC ----
Aps Wss Test Programme ----
VPS ----
Scart Volume Avl Off ----
Pdc Format 1 ----
Pdc Format 2 ----
Name ----
WSS ----
1-8 (No.YA235)
SECTION 3
DISASSEMBLY
3.1 DISASSEMBLY PROCEDURE
NOTE:
· Make sure that the power cord is disconnected from the outlet.
· Pay special attention not to break or damage the parts.
· When removing each board, remove the connectors as required. Taking notes of the connecting points (connector numbers)
makes service procedure manageable.
· Make sure that there is no bent or stain on the connectors before inserting, and firmly insert the connectors.
3.1.1 REMOVING THE STAND 3.1.6 REMOVING THE SIDE CONTROL PWB
(1) Remove the 2 screws [A], then remove the STAND · Remove the STAND.
COVER. · Remove the REAR COVER.
(2) Remove the 4 screws [B], then remove the STAND. (1) Remove the 3 screws [K], then remove the SIDE
CONTROL PWB.
3.1.2 REMOVING THE REAR COVER
· Remove the STAND. 3.1.7 REMOVING THE SPEAKER
(1) Remove the JACK COVER (L/R). · Remove the STAND.
(2) Remove the 7 screws [C], then remove the REAR COVER. · Remove the REAR COVER.
(1) Remove the 4 screws [L], then remove the SPEAKER.
3.1.3 REMOVING THE MAIN PWB
· Remove the STAND. 3.1.8 REMOVING THE LED PWB
· Remove the REAR COVER. · Remove the STAND.
(1) Remove the 2 screws [D], then remove the TERMINAL · Remove the REAR COVER.
BASE. (1) Remove the 1 screw [M], then remove the LED PWB.
(2) Remove the 7 screw [E], then remove the MAIN PWB.
3.1.9 REMOVING THE LCD PANEL UNIT
3.1.4 REMOVING THE INVERTER PWB · Remove the STAND.
· Remove the STAND. · Remove the REAR COVER.
· Remove the REAR COVER. (1) Remove the 4 screws [P] and the 2 screws [Q], then
(1) Remove the 2 screws [F] then remove the SHIELD remove the MAIN BASE.
COVER. (2) Remove the 4 screws [R]. then remove the LCD PANEL
(2) Remove the 2 screws , then remove the INVERTER PWB. UNIT.
NOTE:
· Pay special attention not to break or damage on the LCD
3.1.5 REMOVING THE AV JACK PWB PANEL face or frame.
· Remove the STAND. · The LCD PANEL UNIT is fixed to the FRONT COVER (at the
· Remove the REAR COVER. back side) by using double-side adhesive tapes. To remove
(1) Remove the 2 screws [H], then remove the SIDE CONTROL the LCD PANEL UNIT, remove the adhesive tape on the
BASE with AV JACK PWB. FRONT PANELslowly.
(2) Remove the 2 screws [J], then remove the AV JACK PWB.
(No.YA235)1-9
REAR COVER
C
A
STAND COVER
MAIN PWB
E
B
D
TERMINAL BASE STAND
SIDE CONTROL PWB
K
F
P
Q
SHIELD COVER
G
MAIN BASE
R
INVERTER PWB
LCD PANEL UNIT
L
AV JACK PWB
J
L
H
SPEAKER SPEAKER
SIDE CONTROL BASE
M
LED PWB
FRONT
FRONT PANEL
Fig.1
1-10 (No.YA235)
3.2 MEMORY IC REPLACEMENT
· This model uses the memory IC.
· This memory IC stores data for proper operation of the video and drive circuits.
· When replacing, be sure to use an IC containing this (initial value) data.
3.2.1 SETTINGS OF FACTORY SHIPMENT
3.2.1.1 BUTTON OPERATION 3.2.1.2 REMOTE CONTROL DIRECT OPERATION
Setting item Setting position Setting item Setting position
POWER Off ZOOM AUTO
TV/AV TV
3.2.1.3 REMOTE CONTROL MENU OPERATION
(1) PICTURE (3) FEATURES
Setting item Setting position Setting item Setting position
MODE Bright Sleep Timer Off
Contrast 36 Step Child Lock Off
Bright-1 26 Step Language English
Sharpness 11 Step EXT-2 Output TV
Colour 39 Step Blue Back Off
Bright-2 31 Step
(4) Install [TV MODE]
Colour Temp. Cool
Setting item Setting position
Nolse Red. Min
Colour System Auto
(2) SOUND Decorder(EXT-2) Off
Setting item Setting position VCR Off
Volume 10 Step
(5) Install [EXT MODE]
Bass 16 Step
Setting item Setting position
Treble 15 Step
Colour System Auto
Balance 16 Step
VCR Off
Hyper Sound Off
Sound Mode Mono
(No.YA235)1-11
3.3 REPLACEMENT OF CHIP COMPONENT
3.3.1 CAUTIONS
(1) Avoid heating for more than 3 seconds.
(2) Do not rub the electrodes and the resist parts of the pattern.
(3) When removing a chip part, melt the solder adequately.
(4) Do not reuse a chip part after removing it.
3.3.2 SOLDERING IRON
(1) Use a high insulation soldering iron with a thin pointed end of it.
(2) A 30w soldering iron is recommended for easily removing parts.
3.3.3 REPLACEMENT STEPS
1. How to remove Chip parts 2. How to install Chip parts
[Resistors, capacitors, etc.] [Resistors, capacitors, etc.]
(1) As shown in the figure, push the part with tweezers and (1) Apply solder to the pattern as indicated in the figure.
alternately melt the solder at each end.
(2) Grasp the chip part with tweezers and place it on the
solder. Then heat and melt the solder at both ends of the
chip part.
(2) Shift with the tweezers and remove the chip part.
[Transistors, diodes, variable resistors, etc.]
[Transistors, diodes, variable resistors, etc.]
(1) Apply solder to the pattern as indicated in the figure.
(1) Apply extra solder to each lead. (2) Grasp the chip part with tweezers and place it on the
solder.
(3) First solder lead A as indicated in the figure.
SOLDER SOLDER
A
(2) As shown in the figure, push the part with tweezers and
alternately melt the solder at each lead. Shift and remove B
the chip part.
C
(4) Then solder leads B and C.
A
B
NOTE :
After removing the part, remove remaining solder from the C
pattern.
1-12 (No.YA235)
SECTION 4
ADJUSTMENT
This service manual does not describe ADJUSTMENT.
SECTION 5
TROUBLESHOOTING
This service manual does not describe TROUBLESHOOTING.
(No.YA235)1-13
Victor Company of Japan, Limited
AV & MULTIMEDIA COMPANY DISPLAY CATEGORY 12, 3-chome, Moriya-cho, Kanagawa-ku, Yokohama-city, Kanagawa-prefecture, 221-8528, Japan
(No.YA235)
Printed in Japan
VPT
SCHEMATIC DIAGRAMS
LCD PANEL TELEVISION
6
2005
YA235
LT-20E50SJ,
LT-20E50SU,
LT-20E50SU/Z
CD-ROM No.SML200508
DVD
TV
VCR
MENU
BACK
P
PC
TV
COPYRIGHT © 2005 Victor Company of Japan, Limited No.YA235
2005/8
LT-20E50SJ, LT-20E50SU, LT-20E50SU/Z
STANDARD CIRCUIT DIAGRAM
NOTE ON USING CIRCUIT DIAGRAMS
1.SAFETY Type
The components identified by the symbol and shading are No indication : Ceramic capacitor
critical for safety. For continued safety replace safety ciritical MM : Metalized mylar capacitor
components only with manufactures recommended parts. PP : Polypropylene capacitor
MPP : Metalized polypropylene capacitor
MF : Metalized film capacitor
2.SPECIFIED VOLTAGE AND WAVEFORM VALUES
TF : Thin film capacitor
The voltage and waveform values have been measured under the BP : Bipolar electrolytic capacitor
following conditions. TAN : Tantalum capacitor
(1)Input signal : Colour bar signal (3)Coils
(2)Setting positions of No unit : [µH]
each knob/button and Others : As specified
variable resistor : Original setting position
(4)Power Supply
when shipped
(3)Internal resistance of tester : DC 20k/V : B1 : B2 (12V)
(4)Oscilloscope sweeping time :H 20µs / div
: 9V : 5V
:V 5ms / div
Respective voltage values are indicated
: Othters Sweeping time is
specified (5)Test point
(5)Voltage values : All DC voltage values : Test point : Only test point display
Since the voltage values of signal circuit vary to some extent
according to adjustments, use them as reference values. (6)Connecting method
: Connector : Wrapping or soldering
3.INDICATION OF PARTS SYMBOL [EXAMPLE]
In the PW board : R209 R209 : Receptacle
(7)Ground symbol
4.INDICATIONS ON THE CIRCUIT DIAGRAM
(1)Resistors : LIVE side ground
Resistance value : ISOLATED(NEUTRAL) side ground
No unit : [] : EARTH ground
K : [k] : DIGITAL ground
M : [M]
5.NOTE FOR REPAIRING SERVICE
Rated allowable power
This model's power circuit is partly different in the GND. The
No indication : 1/16 [W]
difference of the GND is shown by the LIVE : ( ) side GND and the
Others : As specified ISOLATED(NEUTRAL) : ( ) side GND. Therefore, care must be
Type taken for the following points.
No indication : Carbon resistor (1)Do not touch the LIVE side GND or the LIVE side GND and the
OMR : Oxide metal film resistor ISOLATED(NEUTRAL) side GND simultaneously. if the above
MFR : Metal film resistor caution is not respected, an electric shock may be caused.
Therefore, make sure that the power cord is surely removed from
MPR : Metal plate resistor the receptacle when, for example, the chassis is pulled out.
UNFR : Uninflammable resistor
(2)Do not short between the LIVE side GND and ISOLATED(NEUTRAL)
FR : Fusible resistor side GND or never measure with a measuring apparatus measure
Composition resistor 1/2 [W] is specified as 1/2S or Comp. with a measuring apparatus ( oscilloscope, etc.) the LIVE side GND
(2)Capacitors and ISOLATED(NEUTRAL) side GND at the same time.
If the above precaution is not respected, a fuse or any parts will be broken.
Capacitance value
1 or higher : [pF] Since the circuit diagram is a standard one, the circuit and
circuit constants may be subject to change for improvement
less than 1 : [µF] without any notice.
Withstand voltage
No indication : DC50[V] NOTE
Due improvement in performance, some part numbers show
Others : DC withstand voltage [V]
in the circuit diagram may not agree with those indicated in
AC indicated : AC withstand voltage [V] the part list.
Electrolytic Capacitors When ordering parts, please use the numbers that appear
47/50[Example]: Capacitance value [µF]/withstand voltage[V] in the Parts List.
(No.YA235)2-1
CONTENTS
SEMICONDUCTOR SHAPES ......................................................................2-2
BLOCK DIAGRAM ........................................................................................2-3
CIRCUIT DIAGRAMS
MAIN PWB CIRCUIT DIAGRAM ................................................................................................................ 2-5
AV JACK/ HEADPHONE PWB CIRCUIT DIAGRAM ................................................................................. 2-19
CONTROL PWB CIRCUIT DIAGRAM ...................................................................................................... 2-20
LED PWB CIRCUIT DIAGRAM ................................................................................................................. 2-20
PATTERN DIAGRAMS
MAIN PWB PATTERN .............................................................................................................................. 2-21
AV JACK/ HEADPHONE PWB PATTERN ................................................................................................. 2-25
CONTROL PWB PATTERN ...................................................................................................................... 2-25
LED PWB PATTERN ................................................................................................................................ 2-25
USING P.W. BOARD
P.W.B ASS'Y name LT-20E50SJ LT-20E50SU LT-20E50SU/Z
CONTROL P.W. BOARD VE-20180094
LED P.W. BOARD VE-20180117
AV JACK/ HEADPHONE P.W. BOARD VE-20180067
MAIN P.W. BOARD VE-20177794
SEMICONDUCTOR SHAPES
TRANSISTOR
BOTTOM VIEW FRONT VIEW TOP VIEW
CHIP TR
C
E
C
B B C E
E C B E C B B E
(G) (D) (S) E C B
IC
BOTTOM VIEW FRONT VIEW TOP VIEW
1 N
OUT
E
IN 1 N
IN E OUT 1 N
CHIP IC
TOP VIEW
1
N
N
1
2-2(No.YA235)
BLOCK DIAGRAM
TFT-LCD PANEL
SIDE AV
S-VIDEO IN
SDRAM
CVBS IN 2MX32bits Audio Amplifier
LVDS TDA3002D2
24-bit RGB
ADC DS90C385MTD
S-VIDEO CVBS MST9883C MAIN OUT LR
IN LR R (0-7)
B (0-7)
G (0-7)
SCALER V SYNC
H SYNC SC2_OUT_LR SC1_OUT_LR
LINE OUT LR DENTERLACER
OSD GM6015 SC1_IN_LR
MTV130
SUB OUT AUDIO PROCESSOR
SUB WOOFER OUT
MSP3452G
LINE OUT
SC2_IN_LR
HP AMP.
MULTIMEDIA AMMONO IN
CVBS IN LR
TDA1308
S-VIDEO
QSS
CARD READER
MODULE MUX
OPTION
YPbPr IN LR
2Kx8bits