JVC KDS-621 Service manual

SERVICE MANUAL

CD RECEIVER

KD-S621

Contents

Safety precaution Preventing static electricity Disassembly method Adjustment method

LOUD

SEL

DISP

11 12

RPT

RND

MODE

SSM

SCM

Area Suffix

E -------- Continental Europe EX ------------ Central Europe

1-2 1-3 1-4 1-11

Flow of functional operation unit TOC read Maintenance of laser pickup Replacement of laser pickup Description of major ICs

1-12 1-14 1-14 1-15 26

No.49675

Jan. 2002

KD-S621

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

Static electricity in the work area can destroy the optical pickup (laser diode) in devices such as CD players. 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

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.

(conductive sheet) or iron plate

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

CD mechanism ass’y

Damper bracket

Attention when traverse unit is decomposed

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

1.Solder is put up before the card wire is removed from connector on the CD substrate as shown in Figure. (When the wire is removed without putting up solder, the CD pick-up assembly might destroy.)

2.Please remove solder after connecting the card wire with when you install picking up in the substrate.

Front bracket

Feed motor ass’y

FD screw

CD mechanism control board

Soldering

FD gear

Pickup unit

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Disassembly method

Removing the front panel assembly

(See Fig.1)

Press the eject button in the lower right part of the front panel. Remove the front panel assembly from the body.

Front panel assembly

Eject button

Fig.1

Removing the front chassis assembly

(See Fig.2 and 3)

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

Release the four joint tabs a on both sides of the front chassis assembly and remove the front chassis assembly toward the front.

Tab a

Front chassis assembly

Heat sink

Fig.2

Tab a

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Fig.3

Tab a

Front chassis assembly

Removing the heat sink (See Fig.4)

Remove the three screws A on the left side of the body.

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Removing the bottom cover

(See Fig.5 and 6)

Prior to performing the following procedure, remove the front panel assembly, the front chassis assembly and the heat sink.

Turn over the body and unjoint the five joints b with the bottom cover and the body using a screwdriver.

Joints b

Joint b

Heat sink

Fig.4

Rear panel

Fig.5

Bottom cover

Joints b

Bottom cover

Joints b

Joint b

Rear panel

Fig.6

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Removing the main board

(See Fig.7 and 8)

Prior to performing the following procedure, remove the front panel assembly, the front chassis assembly, the heat sink and the bottom cover.

Remove the screw B, the four screws C and the three screws D attaching the rear bracket on the back of the body. Remove the rear panel.

Remove the two screws E attaching the main board on the bottom of the body. Disconnect connector CN501 on the main board in the direction of the arrow.

Rear panel

Fig.7

Main board

Removing the CD mechanism section

(See Fig.9)

Prior to performing the following procedure, remove the front panel assembly, the front chassis assembly, the heat sink, the bottom cover and the main board.

Remove the three screws F attaching the cassette mechanism section on the back of the top chassis.

CN501

Fig.8

CD mechanism section

Fig.9

Top chassis

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Removing the control switch board

(See Fig.10 to 12)

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

Remove the four screws G attaching the rear cover on the back of the front panel assembly.

Unjoint the nine joints c with the front panel and the rear cover.

Remove the control switch board on the back of the front panel.

Joints c

Front panel

Rear cover

Fig.10

Joints c

Rear cover

Front panel

Joints c

Fig.11

Control switch board

Fig.12

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Removing the CD mechanism control board(See Fig.1 and 2)

Unsolder the part f and g on the CD mechanism control board.

Remove the stator fixing the CD mechanism control board and the damper bracket (To remove the stator smoothly, pick up the center part).

Remove the screw F attaching the CD mechanism control board.

Remove the CD mechanism control board in the direction of the arrow while releasing it from the two damper bracket slots i and the front bracket slot j.

Disconnect the flexible wire from connector on the pickup unit.

ATTENTION:

Turn the FD gear in the direction of the arrow to move the entire pickup unit to the appropriate position where the flexible wire of the CD mechanism unit can be disconnected easily (Refer to Fig.2).

CD mechanism ass’y

Front bracket

Damper bracket

Fig.1

Pickup unit

Flexible wire

CD mechanism control board

Shift the lock

FD gear

Loading motor

Pull outward

Fig.2

CD mechanism control board

Front bracket

Fig.3

Front bracket

Pull outward

1-8

Flame

Fig.4

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Removing the loading motor

(See Fig.3 to 5)

Prior to performing the following procedure, remove the CD mechanism control board.

Remove the two springs k attaching the CD mechanism ass’y and the front bracket.

Remove the two screws G and the front bracket while pulling the flame outward.

Remove the belt and the screw H from the loading motor.

Removing the CD mechanism ass’y

(See Fig.1, 6 to 9)

CD mechanism ass’y

Flame

Loading motor

Belt

Fig.5

Damper bracket

Fig.6

Prior to performing the following procedure, remove the CD mechanism control PWB and the front bracket (loading motor).

Remove the three screws I and the damper bracket.

Raise the both sides fix arms and move the fix plates in the direction of the arrow to place the four shafts l as shown in Fig.8 and 9.

Remove the CD mechanism ass’y and the two springs m attaching the flame.

Remove the two screws J and both sides rear damper brackets from the dampers. Detach the CD mechanism ass’y from the left side to the right side.

ATTENTION:

The CD mechanism ass’y can be removed if only the rear damper bracket on the left side is removed.

Fix plate (L)

Fix arm (R)

Fig.7

Rear damper bracket

Fig.8

Rear damper bracket

Fix plate(R)

Fix arm (L)

Damper

Fig.9

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Removing the feed motor ass’y

(See Fig.10)

Prior to performing the following procedure, remove the CD mechanism control board, the front bracket (loading motor) and the CD mechanism ass’y.

Remove the two screws K and the feed motor ass’y.

Removing the pickup unit

(See Fig.10 and 11)

*Prior to performing the following procedure, remove the CD mechanism control board, the front bracket (loading motor), the CD mechanism ass’y and the feed motor ass’y.

Detach the FD gear part of the pickup unit upward. Then remove the pickup unit while pulling out the part n of the FD screw.

Feed motor ass’y

FD gear

Nut push spring plate

FD screw

Pickup unit

Fig.10

Part n

Part O

Pickup unit

Pickup mount nut

Pickup unit

ATTENTION:

Remove the screw L attaching the nut push spring plate and the pickup mount nut from the pickup unit. Pull out the FD screw.

When reattaching the pickuap unit, reattach the part o of the pickup unit, then the part n of the FD screw.

Removing the spindle motor

(See Fig.12 and 13)

Prior to performing the following procedure, remove the CD mechanism control board, the front bracket (loading motor), the CD mechanism ass’y and the feed motor ass’y.

Turn up the CD mechanism ass’y and remove the two springs p on both sides of the clamper arms. Open the clamper arm upward.

Turn the turn table, and remove the two screws M and the spindle motor.

FD screw

Spindle motor

Fig.11

Fig.12

1-10

Fig.13

Adjustment method

KD-S621

Test instruments required for adjustment

1. Digital oscilloscope (100MHz)

2. AM Standard signal generator

3. FM Standard signal generator

4. Stereo modulator

5. Electric voltmeter

6. Digital tester

7. Tracking offset meter

8. Test Disc JVC :CTS-1000

9. Extension cable for check EXTGS004-26P 1

Standard measuring conditions Power supply voltage DC14.4V(10.5~16V) Load impedance 4 (2 Speakers connection) Line out load impedance 20k Output Level Line out 2.0V (Vol. MAX)

How to connect the extension cable for adjusting

Standard volume position Balance and Bass &Treble volume : lndication"0" Loudness : OFF

Frequency Band FM 87.5MHz ~ 108.0MHz MW 522kHz ~ 1620 kHz LW 144kHz ~ 279kHz

Dummy load Exclusive dummy load should be used for AM,and FM. For FM dummy load,there is a loss of 6dB between SSG output and antenna input.The loss of 6dB need not be considered since direct reading of figures are applied in this working standard.

The cardboard is cut in a suitable size. uses for the insulation stand of mechanism.

EXTGS004-26P

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Flow of functional operation until TOC read

Power ON

• When the pickup correctly moves to the inner area of the disc

Set Function to CD

• When the laser diode correctly emits

Microprocessor

commands

FMO TC9462 "53"

FEED MOTOR +TERMINAL

TERMINAL

IC581 "5"

REST SW

• When correctly focused

Focus Servo Loop ON

Disc inserted

Pickup feed to the inner area

Laser emitted

Focus search

Disc rotates

RF signal eye-pattern remains closed

Tracking loop closed

RF signal eye-pattern opens

TOC readout

YES

Microprocessor

commands

"No disc"

display

• When the disc correctly rotates

Microprocessor commands

Spindle motor (-) IC581 "7"

AccelerationAcceleration

0.5 Sec

Rough

Servo

0.5 Sec

Servo CLV

1-12

Jump to the first track

Play

Tracking Servo Loop ON

• RF signal

Rough Servo Mode

CLV Servo Mode (ProgramArea)

CLV Servo Mode (Lead-In Area; Digital: 0)

Feed Section

Is the voltage output at

IC521 pin "53" 5V or 0V?

YES

Is 4V present at both

sides of the feed motor?

YES

Is the wiring for IC521

(90) ~ (100) correct?

Is 6V or 2V present at

IC581 "5" and "6"?

YES

Is 5V present at IC581

pin "11"?

YES

Check the vicinity of

IC521.

Check the feed motor

connection wiring.

NONO

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Check CD 9V

and 5V.

Check the feed motor.

Focus Section

When the lens is

moving:

Does the S-search

waveform appear at

IC581 pins "17" and "18"?

Spindle Section

Is the disk rotated?

YES

Does the RF signal

appear at TP1?

YES

Check IC581.

Check the circuits in the vicinity of IC581

pins "15" ~ "18".

Check the pickup and

its connections.

Is 4V present at IC581

pins "7" and "8" ?

YES

Check the spindle motor

and its wiring.

YES

NO NO

Is 4V present at IC521

pin "55" ?

YES

Check the vicinity of

IC581.

Check IC501 and

IC521.

Is the RF waveform at TP1

distorted?

YES

Proceed to the Tracking

section

Tracking Section

When the disc is rotated

at first:

Is the tracking error signal

output at IC501 "12"?

Check IC521.

Approx. 1.2 V

YES

Check the circuits in the

vicinity of IC501 "19" ~

"24" or the pickup

Check the circuit in the

vicinity of IC501 pins

"2" ~ "12".

YESYES

Check the pickup and

its connections.

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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:ampli tude of eye pattern) will be low.

Is RF output

1.0 0.35Vp-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.

Replace it.

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.

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Play a disc.

Check the eye-pattern at TP1.

Finish.

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