JVC LT-20A5 Service Manual
YA350200511
SERVICE MANUAL
LCD FLAT TELEVISION
LT-20A5,
LT-20A5
/S
TABLE OF CONTENTS
1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 SPECIFIC SERVICE INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
COPYRIGHT © 2005 Victor Company of Japan, Limited
No.YA350
2005/11
SPECIFICATION
Item Contents
Dimensions (W × H × D) 54.1cm × 41.6cm × 9.2cm (TV only)
54.1cm × 47.7cm × 12.6cm (Included Stand)
Mass 9.0kg (TV only)
10.2kg (Included Stand)
TV RF System CCIR B/G, I, D/K, L
Color System PAL / SECAM / NTSC3.58 / NTSC4.43
Sound System A2 (B/G, D/K), NICAM (B/G, I, D/K), NTSC-M
Teletext System FLOF (Fastext), WST (World Standard System)
TV Receiving
Channels
Power Input TV
Power Consumption 60W (Stand-by : 1W)
LCD Panel 20.1V wide aspect (15 : 9)
Screen Size Diagonal : 51.0cm (H : 40.8cm × V : 30.6cm)
Display Pixels Horizontal : 640 pixels x Vertical : 480 pixels (VGA)
Audio Power Output 3W + 3W
Speaker 5.4cm round type × 2
Antenna Terminal 75Ω unbalanced, coaxial
Video/Audio Input [VIDEO-1]
Headphone 3.5mm mini jack × 1
Remote Control Unit RM-C1861 (AA/R6/UM-3 battery × 2)
AC Adapter DA-E061370334
VHF Low
VHF High
UHF
CATV
AC Adapter
S-Video
Video
Audio
[VIDEO-2]
Component
Video
Audio
48.25MHz ~ 158MHz
160MHz ~ 442MHz
442MHz ~ 863.25MHz
Mid : X ~ Z+2, S1 ~ S10
Super : S11 ~ S20
Hyper : S21 ~ S41
DC 12V
AC 110V ~ AC 240V, 50Hz / 60Hz
Mini-DIN 4pin × 1
Y : 1V(p-p), positive (negative sync), 75Ω
C : 0.286V(p-p), (Burst signal), 75Ω
1V(p-p), positive (negative sync), 75Ω, RCA pin jack × 1
500mV(rms), high inpedance, RCA pin jack × 2
RCA pin jack × 3
Y : 1V(p-p), positive (negative sync), 75Ω
Pb/Pr : 0.7V(p-p), 75Ω
500mV(rms), high inpedance, RCA pin jack × 2
NOTE : Design & specifications are subject to change without notice.
1-2 (No.YA350)
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) If any repair has been made to the chassis, it is
recommended that the B1 setting should be checked or
adjusted (See ADJUSTMENT OF B1 POWER SUPPLY).
(6) The high voltage applied to the picture tube must conform
with that specified in Service manual. Excessive high
voltage can cause an increase in X-Ray emission, arcing
and possible component damage, therefore operation under
excessive high voltage conditions should be kept to a
minimum, or should be prevented. If severe arcing occurs,
remove the AC power immediately and determine the cause
by visual inspection (incorrect installation, cracked or melted
high voltage harness, poor soldering, etc.). To maintain the
proper minimum level of soft X-Ray emission, components
in the high voltage circuitry including the picture tube must
be the exact replacements or alternatives approved by the
manufacturer of the complete product.
(7) Do not check high voltage by drawing an arc. Use a high
voltage meter or a high voltage probe with a VTVM.
Discharge the picture tube before attempting meter
connection, by connecting a clip lead to the ground frame
and connecting the other end of the lead through a 10kΩ
2W resistor to the anode button.
(8) 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.
(9) 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
PLACE THIS PROBE
1500 10W
GOOD EARTH GROUND
ON EACH EXPOSED
ME TAL PAR T
(No.YA350)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.
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.
1.2.2 INSTALLATION REQUIREMENTS
Ensure that the minimal distance is maintained, as specified below, between the unit with and the surrounding walls.
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.
Distance recommendations
Avoid improper installation and never position the unit where good ventilation
is impossible.
When installing this TV, distance recommendations must be maintained
between the set and the wall, as well as inside a tightly enclosed area or
150 mm
200 mm 200 mm
150 mm
50 mm
piece of furniture.
Keep to the minimum distance guidelines shown for safe operation.
1.3 PRECAUTIONS
(1) The picture brightness may become uneven on the entire screen according to the environmental temperature. Be sure to use
your monitor set in a specified temperature range for proper display presentation.
(2) Avoid disturbing the heat dissipation from the vent holes provided in the rear, on the top and at the sides. Failure to do so may
result in damaged electronics inside due to the accumulated heat within the unit.
(3) Be sure to install the unit in a well-ventilated place. Also make sure that the ambient temperature is kept in the range of 0 to 35°C.
(4) Avoid operation or storage in high temperature and humidity that exceed the specified limit. Otherwise, the display presentation
may be deteriorated.
(5) This monitor may display a blurred picture when exposed to an extreme environmental conditions. This phenomenon is due to
an intrinsic characteristic of the Liquid Crystal Display (LCD). This is not the failure.
(6) This monitor display uses a Cold Cathode Tube as a backlighting device. The brilliance of this tube (and the monitor display)
may be degraded by time.
1.4 CAUTIONS FOR TRANSPORTATION
The goods may be damaged during transportation caused by poor handling such as throwing, toppling, dropping, etc, giving an excess
force against the LCD device. This may happen even if the packing is rigid and secured. To avoid such adverse situations, give a
proper instruction to the freighter for secured handling. The LCD panel uses a glass plate, which is very fragile against an external
force. Take utmost care to avoid vibration or shock to the panel.
1-4 (No.YA350)
SECTION 2
SPECIFIC SERVICE INSTRUCTIONS
2.1 ABOUT LIQUID CRYSTAL DISPLAY
2.1.1 STRUCTURE OF LIQUID CRYSTAL PANEL
The Liquid Crystal Display used for this unit is of a TFT (Thin Film Transistor) type panel. The structure of this panel is that a TFT
array-formed substrate and the stripe pixel matrix type color filter substrate are pressed together with a liquid crystal filled in between
these materials.
2.1.2 LONG-TERM AFTERIMAGE ON THE LCD
A minute amount of ionic material could be mingled into a liquid crystal substrate in the manufacturing process. By applying the
electricity to the panel the ionic material may be migrated towards one part of the electrodes, causing a long-term afterimage to be
displayed. In practice, when a still image is displayed for a long time, the afterimage may be developed and persisted. To cure this
problem, turn off the unit and then turn on again and arrange displaying an appropriate still image on the portion where the afterimage
is being superimposed.
2.1.3 RESPONSE SPEED OF THE LCD
The LCD is slower than the CRT in terms of the display refresh rate, causing a fast moving picture may be displayed blurred. This is
not fault but caused by an intrinsic characteristic of the LCD.
2.1.4 VIEWING ANGLE OF THE LCD
This LCD uses a wide-angle liquid crystal panel, featuring a low rate of the brightness inversion. When viewed from a far outer angle,
the screen may be displayed with hue variation. Again, this is not fault but caused by an intrinsic characteristic of the LCD.
2.1.5 PIXEL DEFICIENCY OF THE LCD
The liquid crystal panel is manufactured with precise engineering procedure. However, there is a possibility of yielding a little amount
of defective pixels in part on the panel. This is unavoidable feature even if the latest technology is being used for manufacturing the
LCD module.
2.2 IMPORTANT NOTICE WHEN REPLACING COMPONENT PARTS
2.2.1 REPLACING THE LCD MODULE
(1) The LCD panel is fragile against the static charge. Be sure to take an appropriate grounding using a grounding-strap etc. when
to replace the LCD panel.
(2) The LCD is made of glass, which is fragile against the mechanical shock. Use utmost care when handling the LCD panel.
(3) When replacing the panel, first place the panel on the base chassis and then make sure that there is no gap in between the panel
and the chassis. Fix the panel with fixing screws. Turn the unit on with an all-black signal being put in and check if the brightness
is even on the entire screen. If the brightness is not even in some part, slacken the fixing screw nearby until the brightness
becomes even with other parts.
(4) A tightening torque for the fixing screws must be set to 0.294Nm or the less. Applying the torque larger than this limit may result
in the damage on the LCD panel.
(5) Connecting or disconnecting the plugs with the set is being powered may cause the malfunction of the set. Makes sure that the
AC power plug is disconnected from the power source when attempting the replacement work.
2.2.2 REPLACING THE FUSE
Be sure to use the rated fuse. After replacing the fuse, confirm that the insulator is stuck on the shielding surface for secure insulation.
(No.YA350)1-5
SECTION 3
DISASSEMBLY
3.1 DISASSEMBLY PROCEDURE
CAUTION:
• Prior to disassembly, unplug the power cord and AC
adapter from the AC outlet without fail. (Turn the power
"off".)
• When exchanging parts etc. with the front side (LCD
side) facing down, please place a protection sheet
below before starting, so as to prevent scratches on the
front side.
A x4
3.1.1 REMOVING THE CABLE COVER (L/R) AND NECK
COVER (Fig.1)
(1) Remove the 4 claws [A].
(2) Remove the CABLE COVER (L), CABLE COVER (R) and
NECK COVER.
CABLE COVER (L)
CABLE COVER (R) NECK COVER
1-6 (No.YA350)
Fig.1
3.1.2 REMOVING THE STAND ASS'Y (Fig.2)
• Remove the NECK COVER.
(1) Remove the 4 screws [B] and remove the STAND ASS’Y.
3.1.3 REMOVING THE TUNER MODULE (Fig.2)
• Remove the CABLE COVER (R).
(1) Remove the DUMMY COVER by pulling the claw [C].
(2) Remove the 1 claw [C] and remove the TUNER COVER.
(3) Remove the TUNER MODULE by pulling carefully.
3.1.4 REMOVING THE AV JACK MODULE (Fig.2)
• Remove the CABLE COVER (L).
(1) Loosen the 2 screws [D].
(2) Remove the AV JACK MODULE by pulling carefully.
Dx2
DUMMY COVER
C
TUNER COVER
Bx4
TUNER
MODULE
STAND ASS'Y
AV JACK MODULE
Fig.2
(No.YA350)1-7
3.1.5 REMOVING THE REAR COVER (Fig.3)
• Remove the CABLE COVER (L/R) and NECK COVER.
• Remove the STAND ASS’Y.
• Remove the TUNER MODULE.
• Remove the AV JACK MODULE.
(1) Remove the 4 screws [E] and remove the REAR COVER.
CAUTION:
• For the REAR COVER is attached tightly, it is easy to
open from the corner of the REAR COVER.
Ex4
1-8 (No.YA350)
REAR COVER
Fig.3
3.1.6 REMOVING THE MAIN PWB SHIELD (Fig.4, 5)
• Remove the REAR COVER.
(1) Remove the 1 screw [F] and remove the D-SUB COVER.
(Fig.4)
(2) Remove the 1 screw [G] and remove the AUDIO COVER.
(Fig.4)
(3) Remove the 2 screws [H] and remove the MODULE
BRACKETS. (Fig.4)
(4) Remove the 4 screws [I]. (Fig.5)
(5) Remove the MAIN PWB SHIELD by sliding to downside.
(Fig.5)
H
MODULE
H
BRACKET
D-SUB
COVER
F
AUDIO COVER
G
Fig.4
(No.YA350)1-9
Ix2
MAIN PWB
SHIEELD
1-10 (No.YA350)
Ix2
Fig.5
3.1.7 REMOVING THE MAIN PWB (Fig.6)
• Remove the REAR COVER.
• Remove the MAIN PWB SHIELD.
(1) Remove the 1 screw [J].
(2) Disconnect the connectors [P004] / [P006] / [P009] / [P017]
from the MAIN PWB.
(3) Disconnect the connector [P613] from the FRONT
CONTROL PWB.
(4) Remove the 6 screws [K] and remove the MAIN PWB.
NOTE:
• EIt is advisable to take note of the connecting location
(connector number) of the removed connectors.
[P004]
[P006]
[P009]
[P017]
J
MAIN PWB
FRONT
CONTROL
PWB
Kx6
[P613]
Fig.6
(No.YA350)1-11
3.1.8 REMOVING THE LCD PANEL UNIT (Fig.7, 8)
• Remove the REAR COVER.
• Remove the MAIN PWB SHIELD.
• Remove the MAIN PWB.
M x2
(1) Remove the 5 screws [L]. (Fig.7)
(2) Remove the 2 claws [M], 4 claws [N] and 2 claws [O] and
remove the LCD PANEL UNIT and LCD BRACKET. (Fig.7)
(3) Remove the 4 screws [P] and remove LCD BRACKET.
(Fig.8)
Ox2
Nx4
1-12 (No.YA350)
Lx5
Fig.7
x2
P
LCD BRACKET
Px2
Fig.8
(No.YA350)1-13
3.1.9 REMOVING THE INVERTER PWB (Fig.9)
• Remove the REAR COVER.
• Remove the MAIN PWB SHIELD.
• Remove the MAIN PWB.
• Remove the LCD BRACKET.
Qx4
(1) Remove the 2 screws [Q].
(2) Disconnect the connectors from the INVERTER PWB and
remove the INVERTER PWB.
NOTE:
• It is advisable to take note of the connecting location
(connector number) of the removed connectors.
INVERTER PWB
Fig.9
1-14 (No.YA350)
3.1.10 REMOVING THE SPEAKERS (Fig.10)
• Remove the REAR COVER.
(1) Disconnect the connector [P612] from the FRONT
CONTROL PWB.
(2) Strip off the sponges and remove the SPEAKERS.
NOTE:
• It is advisable to take note of the connecting location
(connector number) of the removed connectors.
[P612]
FRONT CONTROL PWB
SPONGE
SPEAKER
SPONGE
SPEAKER
Fig.10
(No.YA350)1-15
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