JVC TH-A25 Service Manual
MB128200312
SERVICE MANUAL
DVD DIGITAL CINEMA SYSTEM
TH-A25
Area suffix
B ------------------------------- U.K.
E ----------- Continental Europe
EN ------------ Northern Europe
EV -------------- Eastern Europe
EE --------- Russian Federation
SOUND
VOLUME
STANDBY/ON
STANDBY
DVD DIGITAL CINEMA SYSTEM TH-A25
SOURCE
TABLE OF CONTENTS
1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 SPECIFIC SERVICE INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15
COPYRIGHT © 2003 VICTOR COMPANY OF JAPAN, LIMITED
No.MB128
2003/12
SPECIFICATION
Center unit (XV-THA25)
Amplifier Front/Center/Rear 30 W per channel, min. RMS at 6 Ω as 1 kHz, with no more than 10% total harmonic distortion
Subwoofer 55 W, min. RMS at 3 Ω as 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
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 freq uency-32 kHz, 44.1 kHz, 48
kHz)
Video Color System PAL
Horizontal Resolution 480 lines
Signa-to-Noise Ratio 68 dB
Output Level VIDEO(Composite) 1.0 V(p-p)/75 Ω
RGB (R) 0.7 V(p-p)/75 Ω
(G) 0.7 V(p-p)/75 Ω
(B) 0.7 V(p-p)/75 Ω
Tuner Tuning Range FM 87.50 MHz - 108.00 MHz
AM 522 kHz - 1 629 kHz
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 230 V , 50 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.MB128)
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
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.MB128)1-3
1.5 Safety Precautions (U.K only)
(1) This design of this product contains special hardware and many circuits and components specially for safety purposes. For con-
tinued 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.
(2) Any unauthorised design alterations or additions will void the manufacturer's guara ntee; furthermore the manu facturer cannot
accept responsibility for personal injury or property damage resulting therefrom.
(3) Essential safety critical components are identified by ( ) on the Parts List and by shading on the schematics, and must never
be replaced by parts other than those listed in the man ual. Please note however that many el ectrical and mechanical parts in
the product have special safety related characteristics. These characteristics are often not evident from visual inspection. Parts
other than specified by the manufacturer may not have the same safety characteristics as the recommended replacement parts
shown in the Parts List of the Service Manual and 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 sh ock and fire ha zard. When se rvice is
required, the original lead routing and dress should be observed, and it should be confi rmed that they have been returned to
normal, after re-assembling.
1.5.1 W arning
(1) Service should be performed by qualified personnel only.
(2) This equipment has been designed and manufactured to meet international safety standards.
(3) It is the legal responsibility of the repairer to ensure that these safety standards are maintained.
(4) Repairs must be made in accordance with the relevant safety standards.
(5) It is essential that safety critical components are replaced by approved parts.
(6) If mains voltage selector is provided, check setting for local voltage.
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 (No.MB128)
1.6 Preventing 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.
1.6.1 Grounding to prevent damage by static electricity
Static electricity in the work area can destroy the optical pickup (laser diode) 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 conducti ve sheet) 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
1M
Conductive material
(conductive sheet) or iron palate
(3) Handling the optical pickup
• In order to maintain quali ty during transport and before insta llation, both sides of the la ser diode on the replacemen t optical
pickup are shorted. After replacement, return the shorted parts to their original condition.
(Refer to the text.)
• Do not use a tester to check the condition of the laser diode in the optical pickup. The tester's internal power source can easily
destroy the laser diode.
1.7 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) Cut off the shorted part of the flexible cable using nippers, etc. after replacing the optical pickup. For specific details, refer to the
replacement 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 cable carefully as it may break when subjected to strong force.
(4) I t is not possible to adjust the semi-fixed resistor that adjusts the laser power. Do not turn it.
1.8 Attention when traverse unit is decomposed *Please refer to "Disassembly method" in the text for the DVD pickup unit.
• Apply solder to the short land sections before the flexible wire is disconn ected from the con nector on the DVD servo board. (If the
flexible wire is disconnected without applying solder, the DVD pickup may be destroyed by static electricity.)
• In the assembly, be sure to remove solder from the short land sections after connecting the flexible wire.
(No.MB128)1-5
1.9 Important for laser products
1.CLASS 1 LASER PRODUCT
2.DANGER : Invisible laser radiation when open and inter
lock failed or defeated. Avoid direct exposure to beam.
3.CAUTION : There are no serviceable parts inside the
Laser Unit. Do not disassemble the Laser Unit. Replace
the complete Laser Unit if it malfunctions.
4.CAUTION : The compact disc player uses invisible laser
radiation and is equipped with safety switches which
prevent emission of radiation when the drawer is open and
the safety interlocks have failed or are de
feated. It is dangerous to defeat the safety switches.
5.CAUTION : If safety switches malfunction, the laser is able
to function.
6.CAUTION : Use of controls, adjustments or performance of
procedures other than those specified herein may result in
hazardous radiation exposure.
!
Please use enough caution not to
see the beam directly or touch it
in case of an adjustment or operation
check.
REPRODUCTION AND POSITION OF LABEL and PRINT
WARNING LABEL and PRINT
1-6 (No.MB128)
SECTION 2
SPECIFIC SERVICE INSTRUCTIONS
This service manual does not describe SPECIFIC SERVICE INSTRUCTIONS.
(No.MB128)1-7
SECTION 3
DISASSEMBLY
3.1 Main body section
3.1.1 R emoving 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
1-8 (No.MB128)
3.1.2 Removing the tray door
(See Figs.3 to 6)
• Prior to performing the follow ing procedures, remove the top
cover.
• The following pr ocedures are performe d 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.MB128)1-9
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