JVC G50 Service Manual

MX-G50/MX-G56

SERVICE MANUAL

COMPACT COMPONENT SYSTEM

MX-G50

Area Suffix

MX-G50 / MX-G56

J C

MX-G56

U.S.A.

Canada

Area Suffix

Canada

STANDBY/ON

SUBWOOFER

SLEEP

LEVEL

SOUND

AUX

MODE

FM MODE

+10

FADE

TAPE

FM/AM

TAPE A/B

MUTING

DISC SKIP

VOLUME

RMÐSMXG50A REMOTE CONTROL

Each difference points

MODEL

MX-G50 J MX-G50 C MX-G56 C

CD/DECK/

RECEIVER

CA-MXG50

CA-MXG56

Contents

SP-MXG50

Speaker

SP-MXG50

SP-MXG56

Optical

out

/STOPCDREC START

DISC CHANGE

PLAY & EXCHANGE

MX-G50

TUNING

RANDOM

DUBBING

SET

CANCEL /DEMO

TAPE A

TAPE B

CD SYNCHRO RECORDING

CD-R/RW PLAYBACK

SOUND MODE

COMPACT

DIGITAL AUDIO

SUBWOOFER

LEVEL

PRESET

EJECT

REC/PLAY

STANDBY

STANDBY/ON

PHONES

COMPU PLAY CONTROL

COMPACT COMPONENT SYSTEM

CLOCK

DISPLAY

TIMER

REPEAT PROGRAM

REC START

EJECT

FULL - LOGIC CONTROL

PLAY

CA-MXG50

POWER / SUB / CD EJECT / DISK CHANGER button

SILVER SILVER

METALLIC LIGHT GRAY

SP-MXG50

Color

VOLUME RING

ornament

CD fitting

Safety Precautions Important for laser products Preventing static electricity Disassembly method Wiring connection Adjustment method

1-2 1-3 1-4 1-5 1-20 1-21

Flow of functional operation until TOC read Maintenance of laser pickup Replacement of laser pickup Trouble shooting Description of major ICs

1-25 1-26 1-26 1-27 1-30

No.20913

Feb. 2001

MX-G50/MX-G56

Safety Precautions

1. This design of this product contains special hardware 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 manufacturer`s warranty and will further relieve the manufacture of responsibility for personal injury or proper ty damage resulting therefrom.

3. Many electrical and mechanical par ts 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 or iginal lead routing and dress should be observed, and it should be confirmed that they have been returned to normal, after re-assembling.

5. Leakage currnet check (Electrical shock hazard testing) After re-assembling 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, 1,000 ohms per volt or more sensitivity in the following manner. Connect a 1,500 10W resistor paralleled by a 0.15 F 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 eachexposed metal part, par ticularly any exposed metal part having a return path to the chassis, and meausre 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.).

0.15 F AC TYPE

1500 10W

Good earth ground

AC VOLTMETER (Having 1000 ohms/volts, or more sensitivity)

Place this probe on each exposed metal part.

Warning

1. This equipment has been designed and manufactured to meet international safety standards.

2. It is the legal responsibility 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 components are replaced by approved parts.

5. 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.

1-2

CAUTION

Important for laser products

MX-G50/MX-G56

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 laserradiation and is equipped with safety switches whichprevent 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.

VARNING : Osynlig laserstrålning är denna del är öppnad

och spårren är urkopplad. Betrakta ej strålen.

VARO : Avattaessa ja suojalukitus ohitettaessa olet

alttiina näkymättömälle lasersäteilylle.Älä katso säteeseen.

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.

CAUTION

Please use enough caution not to see the beam directly or touch it in case of an adjustment or operation check.

ADVARSEL : Usynlig laserstråling ved åbning , når

sikkerhedsafbrydere er ude af funktion. Undgå udsættelse for stråling.

ADVARSEL : Usynlig laserstråling ved åpning,når

sikkerhetsbryteren er avslott. unngå utsettelse for stråling.

REPRODUCTION AND POSITION OF LABELS

WARNING LABEL

FUSE CAUTION

FUSE CAUTION LABEL

Power transformer

Bottom shassis

1-3

MX-G50/MX-G56

Preventing static electricity

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.

2. About the earth processing for the destruction prevention by static electricity

In the equipment which uses optical pick-up (laser diode), optical pick-up is destroyed by the static electricity of the work environment. Be careful to use proper grounding in the area where repairs are being performed.

2-1 Ground the workbench

Ground the workbench by laying conductive material (such as a conductive sheet) or an iron plate over it before placing the traverse unit (optical pickup) on it.

2-2 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

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 pickup are shorted. After replacement, return the shorted parts to their original condition. (Refer to the text.)

2. 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.

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. 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. It is not possible to adjust the semi-fixed resistor that adjusts the laser power. Do not turn it

Attention when CD mechanism assembly is decomposed

*Please refer to "Disassembly method" in the text for pick-up and how to detach the CD mechanism assembly.

1. Remove the CD changer unit.

2. Remove the CD changer mechanism.

3. Solder is put up before the card wire is removed from the pickup unit connector on the CD mechanism assembly. (When the card wire is removed without putting up solder, the CD pick-up assembly might destroy.)

4. Please remove solder after connecting the card wire with the pickup unit connector when you install picking up in the substrate.

Card wire

Picup unit connector

Soldering

Fig.2

CD changer unit

Fig.1

Card wire

Picup unit connector

CD changer mechanism

1-4

MX-G50/MX-G56

Disassembly method

Removing the metal cover

(See Fig.1 to 3)

Remove the three screws A attaching the metal cover on the back of the body.

Remove the six screws B attaching the metal cover on both sides of the body.

Remove the metal cover from the body by lifting the rear part of the cover.

ATTENTION:

Do not break the front panel tab fitted to the metal cover.

Fig.1

Metal cover

Optical out

only

MX-G50 J

MX-G56 C

Fig.2

Metal cover

Fig.3

1-5

MX-G50/MX-G56

Removing the CD Tray fitting (1)

(See Fig. 4 to 6)

Prior to performing the following procedure, remove the metal cover.

Press the POWER button. Press the OPEN/CLOSE button to eject the CD tray.

After drawing the lower part of the tray fitting toward the front, remove the five claws a. Then, while moving the tray fitting upward, remove it.

Press the OPEN/CLOSE button to insert the tray.

Removing the CD Tray fitting (2)

(See Fig. 5 to 7)

POWER button

CD tray fitting

CD tray

OPEN/CLOSE button

Fig.4

Joint

- How to eject the CD tray without turning on power -

Turn the black loading pulley gear marked b from the back of the CD changer unit as shown in Fig.7 and draw the CD tray toward the front.

After drawing the lower part of the tray fitting toward the front, remove the five claws a. Then, while moving the tray fitting upward, remove it.

Push and insert the CD tray manually.

(See Fig. 24)

Claw a

Fig.5

CD tray

(Loading pulley gear)

1-6

This slot of the board.

Fig.7

Fig.6

MX-G50/MX-G56

Removing the CD changer unit

(See Fig.8 to 10)

Prior to performing the following procedure, remove the metal cover.

Disconnect the card wire which is attached with adhesive to the left side of the CD changer unit.

Disconnect the card wire from connector CW105 of the CD servo board on the back of the CD changer unit.

Disconnect the harness from connector RCW6 & OCW on the inner side of the main board in the body.

Remove the two screws C attaching the CD changer unit on the back of the body.

Remove the two screws D attaching the CD changer unit on the both side of the body.

CD servo board

CW105

Main board

CD changer unit

OCW

RCW6

Fig.8

Draw the CD changer unit upward from behind while pulling the rear panel outward.

Adhesive card wire strap

CD changer unit

Rear panel

Fig.9

CD changer unit

Rear panel

Fig.10 aFig.10 b

Front panel assembly

1-7

MX-G50/MX-G56

Removing the front panel assembly

(See Fig.11 to 13)

Prior to performing the following procedure, remove the metal cover and the CD changer unit.

Disconnect the card wire from connector FCW3 and the harness from connector JCW1, JCW2 and HCW3 on the inner side of the main board in the body.

Remove the two screws E attaching the front panel assembly on both sides of the body.

Remove the screw F attaching the earth terminal extending from the cassette mechanism assembly.

Remove the screw G attaching the front panel assembly and main board.

Remove the screw H attaching the front panel assembly on the bottom of the body.

Release the two joints c on both sides and two joints d on the bottom of the body using a screwdriver.

Front panel assembly

Joint c

earth wire

Main board

FCW3

JCW2

Fig.11

Main board

JCW1

ACW1

ACW2

HCW3

Front panel assembly

Bottom side

Joint d

Fig.12

Joint c

Joint d

1-8

Fig.13

Removing the heat sink & AMP board

(See Fig.14 and 15)

Prior to performing the following procedure, remove the metal cover and the CD changer unit.

Remove the four screws I attaching the heat sink cover on the back of the body. Remove the heat sink cover.

Remove the four screws J attaching the heat sink & AMP board to the rear panel on the back of the body.

Remove the two screws K attaching the speaker terminal to the rear panel on the back of the body.

MX-G50/MX-G56

Heat sink

cover

Disconnect the card wire from connector ACW1 and the harness from connector ACW2 on the AMP board. (See Fig.11)

After moving the heat sink upward, remove the claws. Then pull out the heat sink & AMP board inward.

Removing the tuner pack

(See Fig.15 and 16)

Prior to performing the following procedure, remove the metal cover and CD changer unit.

Disconnect the card wire from connector CON01 on the tuner board.

Remove the two screws L attaching the tuner pack.

Removing the rear cover (See Fig.17)

Prior to performing the following procedure, remove the metal cover, CD changer unit, heat sink & AMP board and tuner pack.

Remove the fore screws M and one screw M' (Only MX-G50 J / MX-G56 C) attaching the rear panel.

Rear panel

Heat sink

Fig.14

Tuner terminal

Speaker terminal

Fig.15

Main board

CON01

Fig.17

Optical out

only

MX-G50 J

MX-G56 C

Tuner board

Fig.16

1-9

MX-G50/MX-G56

Removing the main Board

(See Fig. 18)

Prior to performing the following procedure, remove the metal cover, CD changer unit, heat sink & AMP board tuner pack and rear cover.

Disconnect the card wire from connector FCW3 and the harness from connector JCW1, JCW2 and HCW3 on the main board.

Disconnect the harness from connector PCW1 on the power transformer board.

Remove the screw G attaching the main board holder. (See Fig.12)

Remove the two screws N attaching the heat sink and bottom chassis.

Removing the power ICs

(See Fig.19 and 20)

Prior to performing the following procedure, remove the metal cover CD changer unit and heat sink & AMP board.

PCW1

Transformer board

FCW3

Fig.18

Heat sink

JCW2

JCW1

HCW3

Main board

Remove the four screws P attaching the power ICs to the heat sink.

Unsolder the power ICs solder point.

Removing the power transformer

(See Fig .21)

Prior to performing the following procedure, remove the metal cover, heat sink & AMP board, tuner pack and rear cover.

Disconnect the power cord from connector RCW2 of the power transformer board.

Disconnect the harness from connector PCW1 of the power transformer board.

Remove the four screws R attaching the power transformer and the screw S attaching the earth terminal.

Power ICs solder point

Power transformer

Fig.19

Fig.20

AMP board

Heat sink

PCW1

1-10

RCW2

Power cord

Fig.21

MX-G50/MX-G56

Prior to performing the following procedure, remove the metal cover, the CD changer unit and the front panel assembly.

Removing the power / CD switch board

(See Fig.22)

Disconnect the card wire from connector UCW1 of the power / CD switch board.

Remove the five screws T attaching the power / CD switch board and release the tab e outward.

Removing the FL display & system control board

(See Fig.22 and 23)

Disconnect the card wire from the connector UCW3, UCW4,UCW5 and UCW6 on the FL & system control board.

Remove the five screws U attaching the FL & system board.

Power / CD switch board

UCW2 UCW3

UCW4

Tab e

FLdiplay & system

control board

UCW5

UCW6

Fig.22

Sound mode knob

Subwoofer knob

Volume knob

Disconnect the card wire from the connector UCW2 on the FL & system control board.

Removing the headphone board

(See Fig.24)

Prior to performing the following procedure remove the FLdisplay & system control board.

You can pull out the headphone board.

Removing the front board (See Fig.24)

Prior to performing the following procedure, remove the FL display & system control board.

Pull out the volume knob, subwoofer knob and sound mode nob from front side.

Remove the ten screws V attaching the front board and release the two tabs f out ward.

Front board

Card wire x

Fig.23

Cassette mechanism assembly

Fig.24

Headphone board

Removing the cassette mechanism assembly (See Fig.24)

Disconnect the card wire x from the mechanism board on the cassette mechanism assembly.

Remove the six screws W attaching the cassette mechanism assembly.

1-11

MX-G50/MX-G56

Prior to performing the following procedure, remove the CD changer unit.

Removing the CD tray (See Fig.25 to 27)

Turn the black loading pulley gear on the under side of the CD changer unit in the direction of the arrow and draw the CD tray toward the front until it stops.

Disconnect the card wire from connector CW103 of the CD servo board on the upper side of the CD changer unit.

Loading pulley gear

CD tray

Fig.25

Push down the two tray stoppers marked g and pull out the CD tray.

Reinstall the CD tray (See Fig.28 to 29)

Align the gear-cam with the gear-tray as shown fig.27, then mount the CD tray.

When assembling the CD tray, take extreme care not engage with gear - synchro.

CD tray

Fig.26

g (Tray stopper)

CD tray

(Tray stopper)

CD servo board

CW103

Fig.27

Gear-cam

Gear-convert

1-12

Gear-tray

Gear-cam

timing point

Gear-tray

CD tray

Fig.28 Fig.29

Gear-synchro

Removing the sensor board / the turn table motor assembly (See Fig.30 to 32)

Prior to performing the following procedure, remove the CD tray.

MX-G50/MX-G56

Remove the screw X attaching the sensor board and release the two tabs h attaching the sensor board on the under side of the CD tray.

Disconnect the harness from connector CW1 on the sensor board and release the harness from the two hooks i. Remove the sensor board.

Remove the screw Y attaching the turn table. Detach the turn table from the tray.

Pull outward the tab marked j attaching the turn table motor assembly on the upper side of the tray and detach the turn table motor assembly from the tray.

Tray

CW1

Sensor board

Fig.29

Turn table

Turn table motor assembly

Fig.31

Fig.32

1-13

MX-G50/MX-G56

Removing the belt, the CD servo board and the switch board (See Fig.33 and 34)

Prior to performing the following procedure, remove the CD tray.

Detach the belt from the pulley on the upper side of the CD changer unit (Do not stain the belt with grease).

Disconnect the card wire from the pickup unit connector on the under side of the CD changer unit.

Attention : Solder is put up before the card wire is removed from the pick-up unit connector on the CD mechanism assembly. (When the card wire is removed without putting up solder, the CD pick-up unit assembly might destroy.)

Disconnect the motor wire harness from connector on the CD servo board.

Remove the screw Z attaching the switch board and release the two tabs k attaching the switch board outward and detach the switch board.

Remove the two screws A' attaching the CD servo board and . First release the n side of the two tabs l and two tabs m attaching the CD servo board motor to raise the CD servo board slightly, then release the CD servo board.

Tabs k

Switch board

CW3

CD changer unit

Fig.33

CD servo board

Tabs m

Soldered parts

Pickup unit connector

Belt

Motor

Tabs l

CD mechanism board

motor connector

If the tabs l and m are hard to release, it is recommendable to unsolder the two soldered parts on the motor terminal of the CD servo board.

Soldering

Card wire

Picup unit connector

Fig.34

1-14

Removing the CD mechanism holder assembly (mechanism included)

(See Fig.35 to 38)

Disconnect the harness from connector on the CD mechanism board in the CD mechanism assembly on the under side of the CD changer unit. Disconnect the card wire from the pickup unit connector.

Attention : Solder is put up before the card wire is removed from the pick-up unit connector on the CD mechanism assembly. (Refer to Fig. 34) (When the card wire is removed without putting up solder, the CD pick-up unit assembly might destroy.)

MX-G50/MX-G56

Motor connecter

CD changer unit

CD mechanism holder assembly

Pickup unit connector

Remove the screw B' attaching the shaft on the right side of the CD mechanism holder assembly. Pull outward the stopper fixing the shaft on the left side and remove the CD mechanism holder assembly from behind in the direction of the arrow y.

Turn the CD mechanism holder assembly half around the lift up slide shaft n of the CD mechanism holder assembly until the turn table is reversed, and pull out the CD mechanism holder assembly.

Lift up slide shaft

Fig.35

Stopper

CD mechanism holder assembly

Fig.36

Lift up slide shaft n

CD mechanism holder assembly

Fig.38

CD mechanism holder assembly

Fig.37

1-15

MX-G50/MX-G56

•

Removing the CD mechanism holder from the CD chager unit. (Refer to "Removing the CD mechanism holder assembly" )

Removing the pickup unit. (

1. Removing the cut washer c on the feed gear sleeve and pull out the feed gear.

2. Remove the two screws A fixing the pickup shaft.

3. Removing the pickup unit.

Removing the motor board.

1. Unsolder the motor terminal on the motor board.

2. Remove the moter board.

Removing the feed motor. (

Remove the two motor fixing screws at B and removing the feed motor.

Removing the spindle motor.

The spindle motor cannot be removed as a single unit. When removing the spindle motor, change the chasis and turntable together as aunit.

See Fig.1)

(See Fig.2)

See Fig.1)

Motor board

Shutter

Cut washer

Fig.1

Unsolder

Shaft

Pickup unit

Feed Gear

Feed motor

Spindle motor

Unsolder

Fig.2

1-16

MX-G50/MX-G56

Removing the record/playback mechanism.

Removing the R/P head.

1. Remove the screw A on the right side of the R/P head.(Fig.1, Fig.2)

2. Remove the screw B on the left side of the R/P head.(Fig.1, Fig.2)

Remove the erase head.

Remove the screw C fixing the erase head.(Fig.1)

Removing the pinch roller.

1. Pull out the pinch roller by opening the pinch roller stopper outward to unlock .(Fig.3)

2. When reassembling the pinch roller, refer to fig. 4 to hook up the spring.

R/P Head

E. Head

Stoppsr

Fig.1

Pinch roller assembly

Spring

Pinch roller

Return spring

R/P Head

Fig.2

Pinch roller

stopper

Fig.3

Pinch roller

spring

Return spring

Fig.4

1-17

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