JVC THA-25 Service manual
MB143200312
SERVICE MANUAL
DVD DIGITAL CINEMA SYSTEM
TH-A25
Area suffix
US ---------------------- Singapore
UB --------------------- Hong Kong
UW ---------- Brazil,Mexico,Peru
UX ------------------- Saudi Arabia
UG - Turkey,South Africa,Egypt
SOUND
VOLUME
STANDBY/ON
STANDBY
DVD DIGITAL CINEMA SYSTEM TH-A25
SOURCE
TABLE OF CONTENTS
1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 SPECIFIC SERVICE INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
COPYRIGHT © 2003 VICTOR COMPANY OF JAPAN, LIMITED
No.MB143
2003/12
SPECIFICATION
Center unit (XV-THA25)
Amplifier Front/Center/Rear 30 W per channel, min. RMS, driven into 6 Ω at 1 kHz, with no more than 10% total harmonic
distortion
Subwoofer 55 W, min. RMS, driven into 3 Ω at 100 Hz, with no more than 10% total harmonic distortion
Audio Audio input sensitivity/Impedance (at 1 kHz)
Analog input AUX ("AUDIO IN") 500 mV/47 kΩ
Signal-to-Noise Ratio 68 dB
Digital input* DIGITAL IN (OPTICAL) -24 dBm to -14.5 dBm (700 nm ±50 nm)
* Corresponding to Linear PCM, Dolby Digital, and DTS Digital Surround (with sampling frequen cy-32 kHz, 44.1 kHz, 48
kHz)
Video Color System NTSC/PAL
Horizontal Resolution 480 lines
Output Level VIDEO OUT (Composite) 1.0 V(p-p)/75 Ω
S-VIDEO (Y):1.0 V(p-p)/75 Ω
(C):0.286 V(p-p)/75 Ω
COMPONENT VIDEO OUT Y 1.0 V(p-p)/75 Ω
PB/PR 0.7 V(p-p)/75 Ω
Tuner Tuning Range FM 87.50 MHz - 108.00 MHz
AM 531 kHz - 1 602 kHz (at 9 kHz intervals)
530 kHz - 1 600 kHz (at 10 kHz intervals)
Usable Sensitivity FM 8.0 dBf (0.9 µV/75 Ω)
AM loop antenna 650 µV/m
General Readable Discs DVD VIDEO, Video CD, Super Video CD, Audio CD, CD-R/RW (Audio CD, Video CD, Super
Video CD, MP3, JPEG), DVD-R/RW (Video format)
Power Requirements AC 110 V - 127 V/220 V - 240 V , Adjustable with the voltage selector, 50 Hz/60 Hz
Power Consumption 110 W (at operation) 2 W (in standby mode)
Dimensions (W × H × D) 360 mm × 65 mm × 404 mm
Mass 6.3 kg
Subwoofer (SP-WA25)
Speaker 15 cm Bass-reflex, magnetically shielded
Power Handling Capacity 55 W
Impedance 3 Ω (min)
Frequency Range 30 Hz to 200 Hz
Dimensions (W × H × D) 210 mm × 382 mm × 338 mm
Mass 6 kg
Satellite Speakers (SP-XTHA25)
Speaker 8 cm Bass-reflex, magnetically shielded
Power Handling Capacity 30 W
Impedance 6 Ω (min)
Frequency Range 80 Hz to 20 kHz
Dimensions (W × H × D) 105 mm × 114 mm × 116 mm
Mass 640 g
Designs & specifications are subject to change without notice.
1-2 (No.MB143)
SECTION 1
PRECAUTION
1.1 Safety Precautions
(1) This design of th is product contains special hardw are and
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. Services should be performed by qualified personnel only.
(2) Alterations of the design or circuitry of the product should
not be made. Any design alterations of the product should
not be made. Any design alterations or additions will void
the manufacturers warranty and will further relieve the
manufacture 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 the Service Manual. The use of a substitute
replacement which does not have the same safety characteristics as the recommended replacement parts shown in
the Parts List of Service Manual may create shock, fire, or
other hazards.
(4) The leads in the products are routed and dressed with ties,
clamps, tubings, barriers and the like to be separated from
live parts, high temperature parts, moving parts and/or
sharp edges for the prevention of electric shock and fire
hazard. When service is required, the original lead routing
and dress should be observed, and it should be confirmed
that they have been returned to normal, after reassembling.
(5) Leakage shock hazard testing
After reassembling the product, always perform an isolation check on the exposed metal parts of the product (antenna terminals, knobs, metal cabinet, screw heads,
headphone jack, control shafts, etc.) to be sure the product
is safe to operate without danger of electrical shock.Do not
use a line isolation transformer during this check.
• Plug the AC line cord directly into the AC outlet. Using a
"Leakage Current Tester", measure the leakage current
from each exposed metal parts of the cabinet, particularly any exposed metal part having a return path to the
chassis, to a known good earth ground. Any leakage current must not exceed 0.5mA AC (r.m.s.).
• Alternate check method
Plug the AC line cord directly into the AC outlet. Use an
AC voltmeter having, 1,000Ω per volt or more sensitivity
in the following manner. Connect a 1,500Ω 10W resistor
paralleled by a 0.15µF AC-type capacitor between an exposed metal part and a known good earth ground.
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. Voltage measured any must
not exceed 0.75 V AC (r.m.s.). This corresponds to 0.5
mA AC (r.m.s.).
AC VOLTMETER
(Having 1000
ohms/volts,
or more sensitivity)
0.15 F AC TYPE
Place this
probe on
1500 10W
Good earth ground
1.2 Warning
(1) This equipment has been designed and manufactured to
meet international safety standards.
(2) It is the legal resp onsibility of the repairer to ensure that
these safety standards are maintained.
(3) Repairs must be made in accordance with the relevant
safety standards.
(4) It is essential that safety critical compone nts are replaced
by approved parts.
(5) If mains voltage selector is provided, check setting for local
voltage.
1.3 Caution Burrs formed during molding may be left over on some parts
of the chassis.
Therefore, pay attention to such burrs in the case of preforming repair of this system.
1.4 Critical parts for safety
In regard with component parts appearing on the silk-screen
printed side (parts side) of the PWB diagrams, the parts that are
printed over with black such as the resistor ( ), diode ( )
and ICP ( ) or identified by the " " mark nearby are critical
for safety. When replacing them, be sure to use the parts of the
same type and rating as specified by the manufacturer.
(This regulation dose not Except the J and C version)
each exposed
metal part.
(No.MB143)1-3
1.5 Preventing static electricity
1.5.1 Grounding to prevent damage by static electricity
Electrostatic discharge (ESD), which occurs when static electricity stored in the body, fabric, etc. is discharged, can destroy the laser
diode in the traverse unit (optical pickup). Take care to prevent this when performing repairs.
1.5.2 About the earth processing for the destruction prevention by static electricity
Static electricity in the work area can destroy the optical pickup (laser dio de) in devices such as DVD players.
Be careful to use proper grounding in the area where repairs are being performed.
(1) Ground the workbench
Ground the workbench by laying conductive material (such as a conductive sh eet) or an iron plate over it before placing the
traverse unit (optical pickup) on it.
(2) Ground yourself
Use an anti-static wrist strap to release any static electricity built up in your body.
(caption)
Anti-static wrist strap
Conductive material
(conductive sheet) or iron plate
1.5.3 Handling the optical pickup
(1) In order to maintain quality during transport and before installation, both sides of the laser diode on the replacement optical pick-
up are shorted. After replacement, return the shorted parts to their orig inal condition. (Refer to the text.)
(2) Do not use a tester to che ck the condition of the laser diode in the optical pickup. T he tester's internal power source can easily
destroy the laser diode.
1.5.4 Handling the traverse unit (optical pickup)
(1) Do not subject the traverse unit (optical pickup) to strong shocks, as it is a sensitive, complex unit.
(2) Remove solder of the short lands on the flexible wire after replacing the optical pickup. For specific details, refer to the replace-
ment procedure in the text. Remove the anti-static pin when replacing the traverse unit.
Be careful not to take too long a time when attaching it to the connector.
(3) Handle the flexible wire carefully as it may break when subjected to strong force.
(4) It is not possible to adjust the semi-fixed resistor that adjusts the laser power. Do not turn it.
1.5.5 Attention when traverse unit is decomposed
*Please refer to "Disassembly method" in the text for the DVD pickup.
• Apply solder to the short circuit points before the flexible wire is disconnected from the connector on the DVD pickup.
(If the flexible wire is disconnected without applying solder, the DVD pickup may be destroyed by static electri city.)
• In the assembly, be sure to remove solder from the short circuit points after connecting the flexible wire.
1-4 (No.MB143)
SECTION 2
SPECIFIC SERVICE INSTRUCTIONS
This service manual does not describe SPECIFIC SERVICE INSTRUCTIONS.
(No.MB143)1-5
SECTION 3
DISASSEMBLY
3.1 Main body section
3.1.1 Removing the top cover
(See Figs.1 and 2)
(1) From the both sides of the main body, remove the four
screws A attaching the top cover. (See Fig.1)
(2) From the back side of the main body, remove the four
screws B attaching the top cover. (See Fig.2)
(3) Take out the top cover in the upward direction while ex-
tending the lower sections of the top cover in the direction
of right and left.
Top cover
AA
Fig.1
B
Top cover Rear panel
Fig.2
1-6 (No.MB143)
3.1.2 Removing the tray door
(See Figs.3 to 6)
• Prior to performing the following procedures, remove th e top
cover.
• The following procedures are performed in the case of power
on.
(1) From the front side of the main body, push the disk open
bottom and eject the disc tray. (See Fig.3)
(2) Release the joints a in the upward dire ction and take out
the tray door. (See Fig.3)
NOTE:
The following procedures are performed in the case of power
off.
(1) From the top side of the main body, remove the four
screws C attaching the DVD top cover. (See Fig.4)
(2) Take out the disc tray in the directi on of the arrow whi le
lifting the section b. (See Fig.5)
(3) Release the joints a in an upward direction and take out
the tray door. (See Fig.6)
(4) Remove the four screws D attaching the DVD mecha-
nism assembly. (See Fig.6)
(5) Disconnect the wires from the connectors AJ1
on the DVD mechanism assembly, and take out
PCN1
the DVD mechanism assembly. (See Fig.6)
(6) Push in the disc tray while lifting the section b. (See
Fig.5)
Reference:
• When pushing in the disc tray, push it until the position of the claw c. (See Fig.5)
(7) Attach the DVD top cover with the four screws C to the
DVD mechanism assembly.
Reference:
• Attaching method of the DVD mechanism assembly
refers to the section 3.1.3.
Joints a Disk open buttonTray door
, AJS1 and
DVD
top cover
C
DVD
mechanism
assembly
C
Fig.4
Claws c
DVD mechanism
assembly
Section b
Disk tray
Fig.3
D
DVD
mechanism
assembly
Tray door
Fig.5
D
AJ1
PCN1
AJS1
D
Joints a
Fig.6
(No.MB143)1-7
3.1.3 Removing the DVD mechanism assembly
(See Fig.7)
• Prior to performing the following procedures, remove the top
cover and tray door.
(1) From the top side of the main body, remove the four screws
D attaching the DVD mechanism assembly.
(2) Disconnect the wires from the conn ectors AJ1
PCN1 on the DVD mechanism assembly, and take out the
DVD mechanism assembly.
, AJS1 and
D
D
JS1
PCN1
AJS1
3.1.4 Removing the front panel assembly (See Figs.8 and 9)
• Prior to performing the following procedures, remove the top
cover and tray door.
(1) From the top side of the main bod y, disconnect the card
wire from the connector UW4
Fig.8)
(2) From the bottom side of the main body, remove the four
screws E attaching the front panel assembly. (See Fig.9)
(3) From the both sides of the main body, remove the two
screws F attaching the front panel assembly. (See Fig.9)
(4) Release the joints d in fo rward direction and take out the
front panel assembly. (See Fig.9)
3.1.5 Removing the tuner pack
(See Figs.8 and 10)
• Prior to performing the following procedures, remove the top
cover.
(1) From the top side of the main bod y, disconnect the card
wire from the connector VW4
(2) Remove the screw G attaching the tuner pack. (See Fig.8)
(3) From the back side of the main body, remove the screw H
attaching the tuner pack. (See Fig.10)
on the function board. (See
on video board. (See Fig.8)
DVD
mechanism
assembly
E
Front panel assembly
Fig.7
Front panel assembly
Fig.8
UW4
D
F
Joint d
3.1.6 Removing the fan motor (See Figs.8 and 10)
• Prior to performing the following procedures, remove the top
cover.
(1) From the top side of the main body, disconnect the fan
motor wire from the connector UW9
(See Fig.8)
(2) From the back side of the main body, remove two screws J
attaching the fan motor. (See Fig.10)
1-8 (No.MB143)
on the function board.
Fan motor
J H
UW9
Fan motor
Video board
Fig.9
Rear panel
Fig.10
Function
board
G
Tuner
pack
VW4
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