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JVC TH-A25 Service Manual
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JVC TH-A25 Service Manual

JVC TH-A25 Service Manual

Dvd digital cinema system
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Download this manual See also: Service Manual, Instruction Manual
SERVICE MANUAL
DVD DIGITAL CINEMA SYSTEM
2003
12
MB143
SOUND
STANDBY
STANDBY/ON
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
TH-A25
DVD DIGIT AL CINEMA SYSTEM TH-A25

TABLE OF CONTENTS

Area suffix
US ---------------------- Singapore
UB --------------------- Hong Kong
UW ---------- Brazil,Mexico,Peru
UX ------------------- Saudi Arabia
UG - Turkey,South Africa,Egypt
VOLUME
SOURCE
No.MB143
2003/12

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Summary of Contents for JVC TH-A25

  • Page 1: Table Of Contents

    UW ---------- Brazil,Mexico,Peru UX ------------------- Saudi Arabia UG - Turkey,South Africa,Egypt SOUND VOLUME DVD DIGIT AL CINEMA SYSTEM TH-A25 STANDBY STANDBY/ON SOURCE TABLE OF CONTENTS PRECAUTION............... . . 1-3 SPECIFIC SERVICE INSTRUCTIONS .
  • Page 2 SPECIFICATION Center unit (XV-THA25) 30 W per channel, min. RMS, driven into 6 Ω at 1 kHz, with no more than 10% total harmonic Amplifier Front/Center/Rear distortion 55 W, min. RMS, driven into 3 Ω at 100 Hz, with no more than 10% total harmonic distortion Subwoofer Audio Audio input sensitivity/Impedance (at 1 kHz)

  • Page 3: Precaution

    SECTION 1 PRECAUTION Safety Precautions (1) This design of this product contains special hardware and voltmeter. many circuits and components specially for safety purpos- Move the resistor connection to each exposed metal es. For continued protection, no changes should be made part, particularly any exposed metal part having a return to the original design unless authorized in writing by the path to the chassis, and measure the AC voltage across...
  • Page 4 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 diode) in devices such as DVD players.

  • Page 5: Specific Service Instructions

    SECTION 2 SPECIFIC SERVICE INSTRUCTIONS This service manual does not describe SPECIFIC SERVICE INSTRUCTIONS. (No.MB143)1-5...

  • Page 6: Disassembly

    SECTION 3 DISASSEMBLY 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 Top cover 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.
  • Page 7 3.1.2 Removing the tray door (See Figs.3 to 6) • Prior to performing the following procedures, remove the top cover. top cover • The following procedures are performed in the case of power (1) From the front side of the main body, push the disk open bottom and eject the disc tray.
  • Page 8 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 connectors AJ1, AJS1 PCN1...
  • Page 9 3.1.7 Removing the rear panel (See Fig.11) • Prior to performing the following procedures, remove the top Rear panel Power cord cover and fan motor. (1) From the back side of the main body, remove the power cord from the rear panel in the direction of the arrow. (2) Remove the screw H, two screws K, five screws L three screws M and attaching the rear panel.
  • Page 10 3.1.10 Removing the main board (See Fig.14) • Prior to performing the following procedures, remove the top Power trans Wire clamp cover, tray door, DVD mechanism assembly, fan motor, rear panel, video board and function board. (1) From the top side of the main body, remove the nine screws P attaching the main board.
  • Page 11 Front panel assembly section 3.2.1 Removing the front board (See Fig.15) • Prior to performing the following procedures, remove the top cover, tray door and front panel assembly. Front board UCW13 Wire Power SW board (1) From the back side of the front panel assembly, remove the five screws R attaching the FRONT board.

  • Page 12: Adjustment

    SECTION 4 ADJUSTMENT This service manual does not describe ADJUSTMENT. 1-12 (No.MB143)

  • Page 13: Troubleshooting

    SECTION 5 TROUBLESHOOTING MAIN 5.1.1 POWER Check for VCC(5V) Check for Input voltage Check for circuit at Sub Trans at FRONT PCB at POWER PCB ;PBD2, PT1, AFS3(Fuse) ;AIC1(7805) ;pin #17,46,72,90 of UIC1 Replace AIC1 Replace AZD1 Check normal Voltage Check resistant from GND Check for power-sense(5V)at FRONT PCB POWER PCB...
  • Page 14 5.1.2 OUTPUT Check voltage at Main PCB Check Connector PW1 ; VM, VL Check ABD2,4 Check Audio channel at CW5 Check Voltage for CW7 for input:5.1 channel Audio signal ; 12V Check circuit for AMP channel Check signal for FR/FL/C/W/RL/RR ;Out ports of FIC6, IC7, RIC5 at MAIN PCB Reference to NEXT page...
  • Page 15 5.1.3 Protection(When High Voltage at Protectiion port) 5.1.3.1 In this case "LOW" for, Base port of Q12(R2003 TR) at MAIN PCB Check voltage for IC4 Check circuit for voltage(-12V) -12V Check Voltage Check ABD 2,4 for Main AMP of Main PCB VM, VL "A"...
  • Page 16 5.1.3.2 In this case "LOW" for Base of Q13(A733) at Main PCB Check the Turn on for channel of Q35(C945) Check circuit for channel(Turn on) according feedback "A"position of previous page 5.1.3.3 Check the Connector Wire Ass'y Connectin of each PCB ;DVD MECHA - Main PCB (8P,PW3) ;POWER TRANS - Main PCB (ACW3) 1-16 (No.MB143)
  • Page 17 DVD Servo parts 5.2.1 Initial operation after power ON POWER ON Tray close operation. Is Tray closed? about 3sec. Pick up head initial position. Is Tray closed? Stop Close operation. Disc present or not Wait Open Command from MPEG Laser Off Disc present Monitor Display=NO DISC CD or DVD judgement...
  • Page 18 5.2.2 Play operation Play Repeat Change Disc Motor forced accelleration seveal times Disc Type Focus Seach Is focus servo Track servo ON CLV servo ON Automatic Adjustment Automatic Adjustment is done once when the disc is replaced Read TOC Search Picture appears 1-18 (No.MB143)
  • Page 19 5.2.3 PickUp Head Initial Position PickUp Head Initial Position (1) 1. Move Pick Up Head to inner direction until pin5 of MJ4="L" (2) 2. If pin5 of MJ4="L", then move Pick Up Head to outer direction for a short time. (3) 3.
  • Page 20 5.2.4 Disc Presence/Absense Judgment Disc Presence Judgment Turn On Laser Does lens move Check Is focus search with UP/DOWN peripheral voltage developed full stroke in focus at pin 11 of SIC1 circuit of DRIC1 direction? Check BUS line between SIC1 and MIC1 Check PI No signal (pin36 of RU1)
  • Page 21 5.2.5 Disc Motor Does Not Rotate Disc Motor Does Not Rotate Is Voltage of 0V developed at Check peripheral circuit of DRIC1 pin15 of SIC1 Check peripheral circuit of SIC1. Check SIC1 5.2.6 Focus Servo does not Work Focus Servo does not Work Check peripheral circuit of SIC1 and Are FE(pin42 of RIC1) and PI(pin36 of RIC1)
  • Page 22 5.2.7 Tracking Servo Does Not Work Tracking Servo Does not Work Check Voltage of Disc Judgment Error PI(pin36 of RIC1) is normal Is TE(pin41 of RIC1) Check peripheral circuit or RIC1 normal? Change PickUp or RIC1 Check peripheral circuit or RCN1 and DRIC1 Change SIC1 Check connection between PCB...
  • Page 23 5.2.8 CLV Servo Does Not Work CLV Servo Does not Work Check peripheral circuit of SIC1 Is XSRFIN(pin2 of SIC1) normal? Check peripheral circuit of DRIC1 Is RF(pin21 of RCN1) Check peripheral circuit of RIC1 normal? Check connection between PCB and MECHA (No.MB143)1-23...
  • Page 24 DVD MPEG Parts 5.3.1 Initial operation after NO POWER ON WAIT Check Reset Voltage at 24pin of LOGO ON "NO DISC" DISPLAY Check Servo parts and MPEG (in time of absence) ATAPI Line Loading Check Servo spindle motor (in time of presence) parts Check Play...
  • Page 25 5.3.2 Logo operation Check Voltage Check 27MHZ crystal of REG2 2.85V FIg.1 REG3 3.50V Check 114MHZ(pin 102 of U13) Fig.1 Check Video signal of Video OK VQ1,VQ3,VQ4,VQ5,VQ6 5.3.3 Audio operation Check Audio Digital signal Check NEW DSP Parts at pin 33,36,37 of U13 Audio out Check Main AMP parts (No.MB143)1-25...
  • Page 26 VICTOR COMPANY OF JAPAN, LIMITED AV & MULTIMEDIA COMPANY AUDIO/VIDEO SYSTEMS CATEGORY 10-1,1chome,Ohwatari-machi,Maebashi-city,371-8543,Japan (No.MB143) Printed in Japan...