Jvc MX-GA77 Service Manual

MX-GA77

SERVICE MANUAL

COMPACT COMPONENT SYSTEM

MX-GA77

					CD 1 CD 2 CD 3
					DISC CHANGE
	ECO
		C O M P A C T C O M P O N E N T S Y S T E M			M X - G A 7 7
	R O C K				D A N C E	REPEAT
	P O P				H A L L	PROGRAM
DUBBING	CLASSIC				STADIUM	RANDOM
			VO	LU
DISPLAY				ME
PHONES			D
		OUN	MODE		PRESET	SET

MP3

SOUND			TAPE A /B
TURBO
	DISPLAY MODE	RDS MODE	SELECT
SUBWOOFER LEVEL
TUNING	TUNING
	BEEP
EJECT			EJECT

Area suffix

B ------------------------

U.K.

E ----

Continental Europe

EN -----

Northern Europe

EV -------

Eastern Europe

SP-MXGA77

CA-MXGA77

SP-MXGA77

Contents

Safety Precautions	1-2
Important for laser produbts	1-4
Preventing static electricity	1-5
Disassembly method	1-6
Wiring connection	1-19
Adjustment method	1-20

Flow of functional operation
until TOC read	1-24
Maintenance of laser pickup	1-25
Replacement of laser pickup	1-25
Trouble shooting	1-26
Description of major ICs	1-30~44

COPYRIGHT 2003 VICTOR COMPANY OF JAPAN, LTD.

No.22083

Jul. 2003

MX-GA77

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 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 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.

AC VOLTMETER

Measure the AC voltage across the resistor with

the AC

(Having 1000

voltmeter.

ohms/volts,

Move the resistor connection to each exposed metal part,

or more sensitivity)

particularly any exposed metal part having a return

path to

0.15 F AC TYPE

the chassis, and meausre the AC voltage across the resistor.

Now, reverse the plug in the AC outlet and repeat each

Place this

measurement. Voltage measured any must not exceed 0.75 V

probe on

each exposed

AC (r.m.s.). This corresponds to 0.5 mA AC (r.m.s.).

1500

10W

metal part.

Good earth ground

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.

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.

(This regulation does not correspond to J and C version.)

1-2

					MA-GA77
				(U.K only)
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.

2.Any unauthorised design alterations or additions will void the manufacturer's guarantee ; furthermore the manufacturer 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 manual. Please note

however that many electrical 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	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 re-assembling.

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.

1-3

MX-GA77

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 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.

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.

REPRODUCTION AND POSITION OF LABELS

CLASS 1
LASER PRODUCT	WARNING LABEL

1-4

MA-GA77

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.

CD changer unit

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

CD changer mechanism

Fig.1

Card wire

Picup unit connector

Fig.2

1-5

MX-GA77

Disassembly method

Removing the metal cover (See Fig.1)

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

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

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

ONE POINT

How to eject the CD tray manually

(see fig.2)

Turn the loading pulley gear at the bottom of the CD changer unit as shown in Fig.2 and draw the CD tray toward the front.

Metal cover

A

B

(both sides)

Fig.1

Loading pulley gear

(See <CD changer unit>fig.1)

Removing the CD tray fitting

(See Fig. 3)

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

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

Fig.2

Joint

CD tray fitting

Removing the CD changer unit

(See Fig.4 to 7)

Prior to performing the following procedure, remove the metal cover and CD tray fitting.

1.Remove the card wire attached to CD changer unit on the adhesion tape.

2.Disconnect the card wire from the connector CW105 on the CD board.

3.Disconnect the harness from the connector CW104 on the main board.

4.Remove the two screws C attaching the CD changer unit to the rear panel.

5.Remove the two screws D attaching the CD changer unit to both sides of the front panel assembly.

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

1-6

Claw

Fig.3

Card wire

CD changer unit

Adhesion tape

Fig.4

MA-GA77

CW105

CD board

C

Rear panel

CD changer unit

CW104

Main board

Fig.5

Removing the front panel assembly

(See Fig.8 to 10)

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

1.Disconnect the card wire from the connector CW101 on the main board.

2.Disconnect the harness from the connector CW108, CW109 and CW110 on the main board.

3.Remove the screw E fixiing the lug wire.

4.Remove the two screws F attaching the front panel assembly to both sides of the body.

5.Remove the screw G attaching the main board to the front panel assembly.

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

7.Release the two joints1 and two joints2, and detach the front panel assembly toward the front.

				Fig.6
Front panel
assembly		CD changer unit
D
(both sides)
				Fig.7			Rear panel
Front panel						Main board
assembly	CW101
		CW109					ACW1
			CW110
				CW108			ACW2

	Amp. board
Joint1
(both sides)	E(fixing the lug wire)
F
(both sides)	Fig.8
	Front panel
	assembly

Main board

G

Joint1 (both sides)

Fig.9	F
	(both sides)

1-7

MX-GA77

Removing the heat sink & amp. board (See Fig.8, 11 and 12)

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

1.Disconnect the card wire from the connector ACW1 and the harness from the connector ACW2 on the amp. board.

2.Remove the four screws I attaching the heat sink cover to the rear panel. Remove the heat sink cover.

3.Remove the four screws J attaching the heat sink and two screws K attaching the speaker terminal to the rear panel.

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

Joint2

H

Fig.10

I

Heat sink cover

I

Removing the tuner board

(See Fig.12 and 13)

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

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

2.Remove the two screws L attaching the tuner board to the rear panel.

Fig.11

J

Claws

Heat sink

	Removing the rear panel	(See Fig.12)

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

1.Remove the three screws M and three screws N attaching the rear panel.

1-8

J

N

Fig.12

CON01

Main board

Fig.13

(Bottom side)

Rear panel

Rear panel

L

K

Speaker terminal

M

Rear panel

Tuner board

Removing the main board (See Fig. 14)

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

CW108

1. Disconnect the card wire from the connector CW101,

and the harness from the connector CW108, Fuse board CW109, CW110 and CW11, and the power cord

from the connector PW103 on the main board.

PCW1

2.Disconnect the harness from the connector PCW1 on the fuse board.

MA-GA77

CW101

CW109

CW110

Main board

Heat sink

PW103

3.Remove the screw G attaching the main board to the front panel assembly. (See Fig.9)

4.Remove the two screws O attaching the heat sink to the bottom chassis.

Removing the power cord (See Fig. 14)

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

1.Disconnect the power cord from the connector PW103 on the main board and pull up the power cord stopper upward.

Removing the power ICs

(See Fig.15 and 16)

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

1.Unsolder the power ICs solder points.

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

Removing the power transformer

(See Fig .17)

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

1.Disconnect the harness from the connector PW102 on the power supply board.

2.Disconnect the harness from the connector PCW1 on the fuse board.

3.Remove the four screws Q attaching the power transformer on the bottom chassis.

PW102	CW11
Bottom chassis	O
	Power cord
Power supply board	Power cord stopper

Fig.14

Power ICs solder point

Heat sink

Amp. board (reverse side)

Fig.15

P	Heat sink

Amp. board

	Fig.16
	Power transformer
	Fuse board
	PCW1
Q	Power supply board
Bottom	PW102
chassis

Fig.17

1-9

MX-GA77

<Front panel assembly>

Prior to performing the following procedure, remove the front panel assembly.

			Removing the CD switch board (See Fig.1)	B
	1.
			Disconnect the card wire from the connector UCW03

on the CD switch board.

2.Remove the five screws A attaching the CD switch board.

			Removing the front board	B
				Connector
			(See Fig.1 and 2)
				Mecha.
	1.		Pull out the sound mode knob, volume knob, and
				board
			preset knob from the front side of front panel
			assembly.
	2.		Disconnect the card wire from the connector UCW02
			on the front board and the connector on the mecha.
			board.
	3.		Remove the fifteen screws B attaching the front
			board.
	4.		Disconnect the card wire from the connector UCW01
			on the front board.

	Front panel assembly (inner side)
A	CD switch board
	UCW03
	Front board
	UCW02
	UCW01

Fig.1

Sound mode knob

Volume knob

Preset knob

Removing the headphone jack board (See Fig.3)

Prior to performing the following procedure remove the front board.

1.	You can pull out the headphone jack board.	Fig.2

Front panel assembly (inner side)

Removing the cassette mechanism assembly (See Fig.3)

1.Disconnect the card wire from the connector on the mecha. board.

2.Remove the six screws C attaching the cassette mechanism assembly.

	Headphone
Connector	jack board
C
Mecha.	C
board
C	Cassette mechanism
(fixing the lug wire)	assembly

Fig.3

1-10

<CD changer unit>

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

Removing the CD tray (See Fig.1 and 2)

1.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.

2.Disconnect the card wire from connector CW103 on the CD board.

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

Loading pulley gear

MA-GA77

CD changer uint (reverse side)

CD tray

CD board

CW103

Fig.1

Reinstall the CD tray (See Fig.3 and 4)

1.Align the gear-cam with the gear-tray as shown fig.3, then mount the CD tray.

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

Gear-cam

Gear-tray

a (Tray stopper)

CD tray

a

(Tray stopper)

CW103

(on the CD board)

Fig.2

Gear-convert	Gear-cam	Gear-synchro
	timing point
	Gear-tray
		CD tray
Gear-convert	Gear-tray
	Fig.3	Fig.4

1-11

MX-GA77

Removing the sensor board (See Fig.5)

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

1.Remove the screw A attaching the sensor board on the CD tray.

2.Remove the sensor board releasing the two tabs a.

3.Disconnect the harness from the connector CW1 on the sensor board.

Removing the turn tray motor

(See Fig.6 and 7)

Prior to performing the following procedure, remove the CD tray and sensor board.

1.Remove the screw B attaching the turn tray. Detach the turn tray from the base tray.

2.Pull outward the tab b attaching the turn tray motor on the base tray and detach the turn tray motor.

Introductory notes:

Base tray + Turn tray = CD tray

CD tray (reverse side)

A

CW1

Tab a

Sensor board

Fig.5

Turn tray

B

Base tray

Fig.6

Turn tray motor

Base tray (upper side)

Tab b

Fig.7

1-12

Removing the belt, the CD board and the switch board (See Fig.8 and 9)

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

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

2.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.)

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

4.Remove the screw C attaching the switch board and release the two tabs e attaching the switch board outward and detach the switch board.

5.Remove the two screws D attaching the CD board. First release the two tabs f and two tabs g attaching the motor, then release the CD board.

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

MA-GA77

Belt

CD changer unit

Fig.8

D CD board

Tabs g

Soldered parts

Tabs e

Motor

Tabs f

C

Switch board

CW3

CD mechanism board motor connecter

Pickup unit connector

Card wire

Soldering	Picup unit
	connector

Fig.9

1-13

MX-GA77

Removing the CD mechanism holder assembly (mechanism included)

(See Fig.10 to 13)

1.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.9)

(When the card wire is removed without putting up solder, the CD pick-up unit assembly might destroy.)

2.Remove the screw E 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.

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

Motor connecter

CD changer unit

CD mechanism holder assembly Pickup unit connector

Fig.10

E

Stopper

CD mechanism holder assembly

Fig.11

Lift up slide shaft n

Lift up slide shaft

y

CD mechanism holder assembly	CD mechanism holder assembly
Fig.13	Fig.12

1-14

<CD mechanism section>

•Removing the CD mechanism holder from the CD chager unit.

(Refer to "Removing the CD mechanism holder assembly" )

	Removing the pickup unit	(See Fig.1)

1.Removing the cut washer 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	(See Fig.2)

1.Unsolder the motor terminal on the motor board.

2.Remove the moter board.

	Removing the feed motor	(See Fig.1)

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.

A

Motor board

Spindle motor

MA-GA77

Shutter

Pickup unit Shaft

A

				Cut washer
	B
			Fig.1		Feed Gear

Unsolder Feed motor

Unsolder

Fig.2

1-15

MX-GA77

<Cassette mechanism section>

Prior to performing the following procedure, remove the cassette mechanism assembly.

Removing the R/P head.

(See Fig.1 and 2)

1.Remove the screw A on the right side of the R/P head.

2.Remove the screw B on the left side of the R/P head.

	Remove the erase head.	(See Fig.1)

1. Remove the screw C fixing the erase head.

R/P Head

Pinch roller

E. Head	C B A

Fig.1

B A

		Spring	R/P Head
			Fig.2
	Remove the pinch roller.	(See Fig.3)	Pinch roller
			stopper

1. Pull out the pinch roller stopper.

2. Pull out the pinch roller.

Pinch roller

Fig.3

1-16

	Removing the motor	(See Fig. 4 to 6)

1.Slide the plastic cover in the direction of the arrow, and remove the three claws. Then remove the plastic cover.

2.Remove the two screws D fixing the motor.

Be careful to grease's splash when the drive belt comes off.

3.Unsolder the motor terminal.

Removing the mechanism board

(See Fig. 5)

1.Unsolder the four solder parts a and the four solder parts b.

2.Remove the two screws E attaching the mecha. board.

Removing the flywheel

(See Fig. 7 and 9)

1.Remove the cut-washer at c from the capstan shaft, then remove the flywheel.

When reassembling the flywheel, be sure to use new washers as they cannot be reused.

MA-GA77

D

Plastic cover

Claw

Fig.4

Motor terminal

Solder	Solder
E part b	part a E Mecha. board

Solder

part a

Motor

Drive belt

Fig.5

Drive belt

Motor

Drive belt

Flywheel

Fig.6

FR belt

Fig.8

c

Sleeve

Washer

FR belt

Capstan

washer

Fig.9

Fig.7

1-17

MX-GA77

< Speaker section >		A	A
	It is exchange in a unit.
	Please do not decompose as much as possible.
	Removing the side panel	(See Fig. 1)

1.Remove the five screws A attaching the side panel and remove the side panel.

A

Removing the side speaker

(See Fig. 2 and 3)

Prior to performing the following procedure, remove the side panel.

1.Remove the four screws B attaching the side speaker.

2.Pull out the side speaker and remove the speaker cord from the speaker terminal.

Side panel

Fig.1

B

Side speaker

Fig.2

Side speaker

Speaker terminal

Fig.3

1-18

3809-001211

3809-001434

CON01

				Tuner board				9
								0
		CW101						CW104 CW103
		CW109			CW110
								CW105
			CW111			Main board
						CW108		PW103
0					CW107			CW11
					9
								CW106
2	9
					0			9
								0
2						0	9	0
								9
		00022A-		CW01B
						0	AH39-00247A
		AH39				9
				Headphone J.board
	0	9		0
		9	0		9
AH39-20002D		8	8	2
							2
					0			0
							9	9	0
							2		8

9

0

3809-001259

0

9

9 2 0

8

19-1

3809-001413			Wiring
CD switch board
AH39-00295A
UCW03	ACW2	Amp. board	connection
3809-001228	ACW1
Front board	0
	9
UCW02
UCW04
UCW01
UCW05

9

0

Power transformer

AH39-00466A

0 9

CW3

CW101

CW104

CW107

CW106 CW105

CD board

9

0

AH39-00060A

AH38-12001A

CW102

CW103

PCW1

AH39-00338A

3809-001121

AH39-20561P

CW2

CW3	CW1
	AAN1

			2
	001034-3809		0
		2	0

PW102

0

9

CD mechanism

0	9	8	7	6	5	4	3	2	1	codesColor
		9	0
Black	White	Gray	Violet	Blue	Green	Yellow	Orange	Red	Brown	.below shown are	-MA
											GA77

MX-GA77

Adjustment method

1. Tuner

* Adjustment Location of Tuner PCB

ITEAM	AM(MW) OSC		AM(MW) RF
	Adjustment		Adjustment
Received FREQ.	522~1629 KHz		594 KHz
Adjustment	MO			MA
point
Output	1~7.0 0.5V		Maximum
			Output(Fig.1)
		MAIN	VT	GND			TESTER
		PCB

Fig.1 OSC Voltage

1-20

FM THD Adjustment

SSG FREQ.

98 MHz

Adjustment

point FM DETECTOR COIL (FM DET)

Output

60 dB

Minumum Distortion (0.4% below) (Fig.2)

MA-GA77

	Output	FM
		Antenna SET
	GND
		Terminal
			Oscilloscope
	FM S.S.G	Input
		Speaker
		Terminal	Input
		output
		Distortion Meter

Fig.2 IF CENTER and THD Adjustment

FM Search Level Adjustment

	SSG FREQ.	98 MHz
	Adjustment	BEACON
	point
		SENSITIVITY
	(SVR1)	SEMI-VR(10K )
	Output	28 dB( 2dB)

Adjust SVR1 (Fig.3)

*Adjust FM S.S.G level to 28dB

AM(MW) I.F Adjustment

SSG FREQ.	450 kHz
Frequency	522 kHz
Adjustment	AM IF
point

Maximum output (Fig.4)

	28 dB	FM Antenna
		SET
FM S.S.G	GND	FM IN

20 k

Fig.3 FM Auto Search Level Adjustment

		60cm
		AM IF
	OUTPUT	AM ANT
		IN
	AM SSG	Speaker Terminal
	450KHZ
	INPUT	OUTPUT

VTVM Oscilloscope

Fig.4 AM I.F Adjustment

1-21

MX-GA77

2. Cassette Deck

To adjust tape speed

Notes

1)Measuring tape:

i) VT-712/MTT-111(or equivalent)

(Tapes recorded with 3kHz)

ii) AC-225/MTT-5512(or equivalent)

2)Connect the cassette deck to the frequency counter as in fig.1.

Cassette Deck

Frequency Counter

SPK OUT

output

Fig.1

Step	Item	Pre-Setup		Pre-Setup	To Adjust	Standard	Remark
		Condition
1	NOR	SPK OUT	1)	Deck 1:VT-712	Turn VSR1 to	3KHz	1%
	SPEED	(connected to the	2)	Press PLAY	left and right		range
	Control	frequency counter)		SW button	(FRONT PCB)
			3)	Deck 2:Same
				as above

To adjust plabyback level/REC

Notes

1)Before the actual adjustment, clean the play/recording head.

2)Measuring tape :

i)VT-703/MTT-114N(or equivalent 10kHz AZIMUTH control)

ii)AC-225/MTT-5512(or equivalent)

3)The cassette deck is connections as shown in fig.2.

MAIN PCB	VTVM		Oscilloscope
SPK OUT
(GND)	In	Out
	Fig.2

1. Adjust Deck 1 Play Level

	Step	Item	Pre-Setup	Pre-Setup	To Adjust	Standard	Remark
			Condition
	1	AZIMUTH	SPK OUT	After putting VT-703	Turn the control	Max output	After
			(VTVM is	into Deck 1	screw to as	and same phase	adjustment
				- Press FWD PLAY	shownin Fig.3.	(both channels)	secure it with
			connected to
				button.			REGION
			the scope)
							LOCK.

1-22

MA-GA77

2. Adjust Deck 2 Play Level/REC BIAS

	Step	Item	Pre-Setup	Pre-Setup	To Adjust	Standard	Remark
			Condition
	1	AZIMUTH	SPK OUT	After putting VT-703	Turn the control	Max output	After
			(VTVM is	into Deck 2	screw to as	and same phase	adjustment
			connected to	1)Press FWD PLAY	shown in Fig.3.	(both channels)	secure it with
			the scope)	button.			REGION
							LOCK.
	2	Recording	Fig.4	After putting AC-225	Turn JSR2L,	CHECK TO
		Bias		into Deck 2	JSR2R to the	7mV( 0.5mV)
		Voltage		1)Press REC PLAY	right and left
				button.
				2)TAPE PCB JCW3,
				connectted to VTVM

Recording /Play head

AZIMUTH control screw (FWD Play)

AZIMUTH control screw
(RVS Play)
	Fig.3
	SET	VTVM		Oscilloscope
Audio OSC.	(MAIN PCB)
	IN	TP
	AUX IN	SPK OUT
		IN	OUT

Fig.4

1-23

MX-GA77

Flow of functional operation until TOC read

		Play Key				Check Point
Power ON				RESET a CD LSI		Confirm that the voltage at the pin17
						of KB9226(IC101) is "L"		"H".

		Tracking error waveform at TOC reading
	Pin 34 of	Approx.3.7sec
	KB9226
	(IC101)
	Approx
	0.4V
	2.50V
		Disc states
		to rotate

LIMIT SW ON

Confirm that the voltage at the pin33

of KB9226(IC101) is "H"

"L"

"H".

SET Default value of

TE gain, TE balance

Automatic adjusting of

focus bias

Automatic adjusting of

FE offset

Automatic adjusting of

TE offset

LASER power ON

Confirm that the voltage at the

pin37 of KB9226(IC101) is 3.5V.

Detection of disk

Confirm that the signal from pin24

Disc is rotated

of KB9226(IC101) is 3.5V as a

accelerated pulse during

approx.1.96s.

Automatic adjusting of

Confirm the waveform of

TE balance

the Tracking error signal

at the pin 34 of KB9226(IC101).

Automatic adjusting of

TE gain

TOC reading

Confirm the eye-pattern

at the pin2 of KB9226(IC101).

Play a disc

1-24

MA-GA77

Maintenance of laser pickup

(1) Cleaning the pick up lens

Before you replace the pick up, please try to clean the lens with a alcohol soaked cotton swab.

(2) Life of the laser diode

When the life of the laser diode has expired, the following symptoms will appear.

1. The level of RF output (EFM output : amplitude of eye pattern) will below.

	Is the level of	NO
	RF OUT under
				Replace it.
	1.1V 0.2Vp-p?

YES

O.K

(3) Semi-fixed resistor on the APC PC board

The semi-fixed resistor on the APC printed circuit board which is attached to the pickup is used to adjust the laser power. Since this adjustment should be performed to match the characteristics of the whole optical block, do not touch the semi-fixed resistor.

If the laser power is lower than the specified value, the laser diode is almost worn out, and the laser pickup should be replaced.

If the semi-fixed resistor is adjusted while the pickup is functioning normally, the laser pickup may be damaged due to excessive current.

Replacement of laser pickup

Turn off the power switch and,disconnect the power cord from the ac outlet.

Replace the pickup with a normal one.(Refer to "Pickup Removal" on the previous page)

Plug the power cord in,and turn the power on. At this time,check that the laser emits for about 3seconds and the objective lens moves up and down.

Note: Do not observe the laser beam directly.

Play a disc.

Check the eye-pattern at TP1.

Finish.

1-25

MX-GA77

Troubleshooting

1. Amplifier

Power malfunction

No output

1-26

MA-GA77

2.Tuner malfunction (FM/AM)

3.Tape

1-27

MX-GA77

4.CD

1-28

MA-GA77

5.CD - MP3 parts

1-29

MX-GA77

Description of major ICs

LC876764 (UIC1) : Microcontroller

1.Pin layout

S47/PF7

S46/PF6

S45/PF5

S44/PF4

S43/PF3

S42/PF2

S41/PF1

S40/PF0

VDD4

S39/PE7

S38/PE6

S37/PE5

S36/PE4

S35/PE3

S34/PE2

S33/PE1

S32/PE0

S31/PD7

S30/PD6

S29/PD5

S28/PD4

S27/PD3

S26/PD2

S25/PD1

S24/PD0

S23/PC7

S22/PC6

80

79

78

77

76

75

74

73

72

71

70

69

68

67

66

65

64

63

62

61

60

59

58

57

56

55

54

S48/PG0

81

S49/PG1

82

S50/PG2

83

S51/PG3

84

P00

85

P01

86

P02

87

P03

88

VSS2

89

VDD2

90

P04

91

P05

92

P06

93

P07

94

P10/SO0

95

P11/SI0/SB0

96

P12/SCK0

97

P13/SO1

98

P14/SI1/SB1

99

P15/SCK1

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

2.Block diagram

P16/T1PWML

P17/T1PWMH/BUZ

P30/INT4/T1IN

P31/INT4/T1IN

P32/INT4/T1IN

P33/INT4/T1IN

P34/INT5/T1IN

P35/INT5/T1IN

P36/INT5/T1IN

P37/INT5/T1IN

RES

XT1/AN10

XT2/AN11

VSS1

CF1

CF2

VDD1

P80/AN0

P81/AN1

P82/AN2

P83/AN3

P84/AN4

P85/AN5

P86/AN6

P87/AN7/MICIN

P70/INT0/T0LCP/AN8

P71/INT1/T0HCP/AN9

Interrupt Control

IR

PLA

Stand-by Control

ROM

CF

Clock Generator

RC

MRC

PC

X’ tal

Bus Interface

ACC

SIO0

Port 0

B Register

SIO1

Port 1

C Register

Timer 0

Port 3

(High speed clock counter)

AL U

Timer 1

Port 7

Base Timer

Port 8

PSW

VFD Controller

ADC

RAR

INT 0 - 5

Weak Signal

RAM

Noise Rejection

Detector

Timer 4

Timer 6

Stack Pointer

Timer 5

Timer 7

Watch Dog Timer

1-30

S21/PC5		S20/PC4
53		52

28		29
P72/INT2/T0IN/NKIN/AN12		P73/INT3/T0IN/AN13

FIX0

51

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

32

31 30

S0/T0

S19/PC3

S18/PC2

S17/PC1

S16/PC0

VDD3

S15/T15

S14/T14

S13/T13

S12/T12

S11/T11

S10/T10

S9/T9

S8/T8

S7/T7

S6/T6

S5/T5

S4/T4

S3/T3

S2/T2

S1/T1