JVC KD-S785 Service Manual

SERVICE MANUAL

CD RECEIVER

KD-S785

SOUND

ATT

SOURCE

VOL

LOUD

DISP

45Wx4

KD-S785

SCAN

RPT RND SCM

TUNER

KD-S785

Contents

Safety precaution Preventing static electricity Disassembly method Adjustment method

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

Area Suffix

U Other Areas

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

1-12 1-14 1-14 1-15~33

No.49748

Jun. 2002

KD-S785

Safety precaution

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.

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

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KD-S785

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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KD-S785

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, 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.

KD-S785

Removing the bottom cover

(See Fig.5, 6)

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

Turn the body upside down.

Insert a screwdriver to the two joints b and two joints c on both sides of the body and the joint d on the back of the body, then detach the bottom cover from the body.

CAUTION:

When disengaging the joint d using a screwdriver, do not damage or break the board.

Joint d

Joint b

Heat sink

Fig.4

Rear panel

Fig.5

Bottom cover

Joint c

Bottom cover

Joint b

Joint c

Joint d

Rear panel

Fig.6

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KD-S785

Removing the main board (See Fig.7, 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

CCC

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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KD-S785

Removing the control switch board

(See Fig.10 ~ 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 eleven joints e with the front panel and the rear cover.

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

Joint e

Front panel

Rear cover

Fig.10

Joint e

Front panel

Rear cover

Joint e

Fig.11

Control switch board

Fig.12

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KD-S785

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

Unsolder the part a and b 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 A 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 d and the front bracket slot e.

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 assembly

Front bracket

Pickup unit

Damper bracket

Fig.1

Flexible wire

CD mechanism control board

Shift the lock

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 f attaching the CD mechanism assembly and the front bracket.

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

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

Loading motor

FD gear

Loading motor

Pull outward

Fig.2

CD mechanism control board

Front bracket

Fig.3

Front bracket

Pull outward

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Fig.5

Belt

Flame

Fig.4

KD-S785

Removing the CD mechanism assembly

(See Fig.1, 6 to 9)

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

Remove the three screws D 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 g as shown in Fig.8 and 9.

Remove the CD mechanism assembly and the two springs h attaching the flame.

Remove the two screws E and both sides rear damper brackets from the dampers. Detach the CD mechanism assembly from the left side to the right side.

ATTENTION:

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

CD mechanism

Front bracket

CD mechanism

Flame

assembly

Damper bracket

Fig.5

Damper bracket

Fig.6

CD mechanism control board

Fix arm (R)

Fix plate (L)

Fig.7

Rear damper bracket

Fig.8

Rear damper bracket

Fix plate(R)

Fix arm (L)

Damper

Fig.9

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KD-S785

Removing the feed motor assembly

(See Fig.10)

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

Remove the two screws F and the feed motor assembly.

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 assembly and the feed motor assembly.

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

Feed motor assembly

FD gear

Nut push spring plate

FD screw

Pickup unit

Fig.10

Part i

Part j

Pickup unit

Pickup mount nut

Pickup unit

ATTENTION:

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

When reattaching the pickup unit, reattach the part j of the pickup unit, then the part i 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 assembly and the feed motor assembly.

Turn up the CD mechanism assembly and remove the two springs k on both sides of the clamper arms. Open the clamper arm upward.

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

FD screw

Spindle motor

Fig.11

Fig.12

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Fig.13

Adjustment method

KD-S785

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 oout impeadance 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 BBE : OFF

Frequency Band FM 87.5MHz ~ 108.0MHz AM 531kHz ~ 1602 kHz

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.

EXTGS004-26P

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