JVC PC x250b Service Manual

SERVICE MANUAL

CD PORTABLE COMPONENT SYSTEM

PC-X250

Unit No SP-PCX250

Contents

Safety precaution ------------------ 2 Block/Wiring Diagram ------------------ 25 Disassembly method -------------- 4 Circuit Diagram -------------------------- 27 Adjustment method ---------------- 6 PCB drawing ----------------------------- 29 TOC read ---------------------------- 10 Assembly ---------------------------------- 32 Major IC Description -------------- 11 Packing ------------------------------------ 42

Unit No CA-PCX250

Area Suffix J ---- USA C ---- Canada

Unit No SP-PCX250

No. 28001

Oct. 2001

PC-X250

CAUTION

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 ti the original design unless authorised in writing by the manufacturer. Replacement parts must be identical to those used in the original circuits. Services should be performed by qualified personel 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 manufacturer of responsibility for personal injury or property damage resulting therefrom.

3. Many eletrical 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 obtain by using replaement components rated for higher voltage, the Parts List of Service manual. Electrical components having such features ate identified by the shading on the schematics and by ( repalcement 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, tubing's, barriers and the like to be separated from live parts, high temperatures parts, moving parts and/or sharp edges for the prevention of electric shcok and fire hazard. When service is required, the original leat routing and dress should be observed, and it should be confirmed that they have been returned to normal, after re-assembling.

! ) on the parts List in the Service Manual. The use of a substitute

5. Leakage current check (Electrical Shock hazard testing) After re-assembling the product, always perform an isolation check on the exposed metap 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 isloation 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 ecposed metal parts of the cabinet, particularly and 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 sensitvity in the following manner. Connect a 1,500 ohm 10W resistor paralleled by a

0.15uF 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 each exposed metal part, particularly and exposed metal part having a return path to te chassis and measure 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.).

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. It mains voltage selector is provided, check setting for local voltage.

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Warning

Burrs formed during moulding may be left over on some parts of the chassis. Therefore, pay attention to such burrs in the case of performing repair of this system.

PC-X250

Preventing 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 pcikup). Take care to prevent this when performing repairs.

1.1. Grounding to prevent damage by static electricity

Static electricity in the work area can destroy the optical pickup (laser diode) in devicessuch as DVD players.

Be careful to use proper grounding in the area where repairs are being performed.

1.1.1. Gound 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.

1.1.2. Ground yourself

Use an anti-static wrist starp to release and static electricity built up in your body.

1.1.3. Handling the optical pcikup

In order to maintain quality during transport and before installation, both sides of the laser diode on the

replacement optical pickup are storted. After replacement, return the shorted parts to their original condition.

(Refer to the text.)

Do not use a tester to check the condition of the laserdiode in the optical pickup. The tester's internal power

source can easily destory the laser diode.

1.2. Handling the traverse unit (optical pickup)

Do not subject the traverse unit (optical pcikup) to strong shocks, as it is a sensitive, complex unit.

Cut off the shorted part of the flexible cable using nippers, etc. after replacing the optical pickup. For specific

details, refer to the replacement procdeure in the text. Remove the anti-static pin when replacing the traverse

unit. Be careful not to take too long a time when attaching itto the connector.

Handle the flexible cable carefully as it may break when subjected to strong force.

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

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PC-X250

Disassembly method

Removing the rear panel

From behind the body, remove the Five screws

retaining the rear panel.

Then remove the Two screws

retaining the bottom of rear panel.

Take out the rear panel from the body.

Note:

Be careful of the FM antenna white wire, it is connection with the tuner PCB up side.

You can directly take out from the tuner PCB.

When you re-assembly the product, plug the FM antenna white wire into the Tuner PCB's

"FM ANT" position.

Screw A.

Screw B.

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Removing the Audio Board

1.Open & remove the rear panel

2. Remove the Connector CN201, CN202, CN203, CN405, CN502, CN801 & CN301 on the Audio Board.

3. Remove the two Screws C retaining the Audio Board.

CN202 Screw C

CN201

CN502

CN203

CN801 CN405

CN301

PC-X250

Removing the CD Mechanism

1 Open & remove the rear panel

2 Remove the Audio PCB

3 Remove the Two Screws D retaining the CD Tray Backet.

Removing the Tuner PCB Screw E

1 Open & remove the rear panel.

2 Remove the Audio PCB.

3 Remove CD mechanism.

Screw D

4 Remove the Eight Screws E retaining

on the Tuner Board.

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PC-X250

Adjustment method

Measurement instruments required for Tuner section

adjustment

Low frequency oscillator Voltage applied to tuner ---------- +B:DC 4.9V

This oscillator should have a capacity to output VT:DC 12V

0dBs to 600 at an oscillation frequency of Reference measurement ----- 26.1mV(0.28V)/3

50Hz-20KHz output

Input positions ----- AM : Standard loop antenna

Electronic voltmeter FM : TP1 (hot) and TP2 (GND)

Distortion meter

Frequency counter Standard measurement position of volume

Wow & flutter meter

Test tape Bass ----------------------------------------------------- Off

TCC-112 : Tape speed and running unevenness (3KHz) Active hoper bass pro ------------------------ Off

TCC-140 : Reference level (1KHz) Up and down adjustment of volume ----- Vol : 23

TCC-182A : Head angle (8KHz) , playback frequency

characteristics (1KHz) and dubbing frequency Precautions for measurement

characteristics (125Hz and 8KHz) 1 Apply 30PF and 33 Kohm to the IF sweeper output

Because of frequency - mixed tape with 63 , 1 , 10 and side and 0.082UF and 100 Kohm in series to the

14KHz (250nWb/m -24dB) , use this tape together sweeper input side .

with a filter . 2 The IF sweeper output level should be made as

Black tape low as possible within the adjustable range .

TYPE I : AC - 225 3 Since the IF sweeper is a fixed device , there is no

TYPE II : AC - 514 need to adjust this sweeper .

8 Torque gauge : For play and back tension 4 Since a ceramic oscillator is used , there is no need

FWD(TW2111A) , REV(TW2121a) and FF/REW(TW2231A) to perform any MIX adjustment .

5 Since a fixed coil is used , there is no need to

Measurement conditions adjust the FM tracking .

6 The input and output earth systems are separated .

Power supply voltage ---------------- AC 120V (60Hz) In case of simultaneously measuring the voltage in

Reference output -------------- Speaker : 0.866V/3 both of the input and output systems with an

Headphone : 0.245V/32 electronic voltmeter for two channels , therefore , the

Reference frequency and ----- 1KHz , AUX : 450~500mV earth should be connected particularly carefully .

input level 7 In the case of BTL connection amp. , the minus

Input for confirming recording and ------- AUX : -28dBs terminal of speaker is not for earthing . Therefore , be

playback characteristics sure not to connect any other earth terminal to this

Measurement output terminal ---------- Speaker J3002 terminal . This system is of an BTL system .

* Load resistance --------------------------- 3 8 For connecting a dummy resistor when measuring

the output , use the wire with a greater code size .

Radio Input signal 9 Whenever any mixed tape is used , use the band

pass filter (DV-12V)

AM frequency -------------------------------- 400Hz

AM modulation ---------------------------------- 30%

FM frequency --------------------------------- 1 KHz

FM frequency deviation ------------------------ 22.5KHz

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TAPE DECK ADJUSTMENTS

1 HEAD AZIMUTH ADJUSTMET

( 1 ) Load the test tape TCC-182A 8KHz for azimuth

adjustment. ( 2 ) Press the PLAY button. ( 3 ) Use a cross-tip screwdriver to turn the screw for azimuth

adjustment so that the left and right output are maximized ( 4 ) Press the STOP button ( 5 ) After completion of the adjustment. Use thread lock(TB-1401B)

to secure the azimuth-adjustment screw.

2 AC BIAS FREQUENCY ADJUSTMENTS

( 1 ) Connect frequency counter to CN202(BS); ( 2 ) R/P swith in recording state; ( 3 ) Adjusting T801 use a plastic screwdriver, AC bias frepuency ;61kHz +/- 1kHz..

PC-X250

3 TAPE SPEED ADJUSTMENT

( 1 ) Insert the test tape(MTT-111N,3,000 HZ) ( 2 ) Press the PLAY button. ( 3 ) Use a flat-tip screwdriver to turn the VR 501.

Adjust VR501 so that the frequency counter become 3,000Hz

TAPE HEAD AND SPEED ADJUSTMENT DIAGRAM

CASS DECK

E HEAD

L. SW

P/R HEAD

P HEAD

A DECK B DECK

L. SW

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PC-X250

Tape recorder section

Items Measrrnment methed

Confirmation Test tape 1 Playback the test tape TCC-182A (8KHz) Maximum Adjust the head

of head angle :TA-182A(8KHz) 2 With the recording & playback mechanism, output azimuth screw

Confirmation Test tape Adjust VR501 so that the frequrncy counter Tape speed VR501

of tape speed :TCC-112(3000Hz) reading becomes 3,010Hz +/-15Hz when of deck

Measurement Standard Adjusting]

conditions Values positions

Measurement output adjust the head azimuth screw so that the only when the

terminal left and right output levers become head has been

:Speaker terminal maximum, After adjustment, lock the head changed

Sperker R azimuth at least by half turn.

(Load resistance:3 )

:Headphone terminal

playing back the test tape TCC-112 (3000Hz) with :3,010Hz

Measurement output playback and recording mechanism after +/-15Hz

terninal ending forward winding if the taoe.

:Headphone terminal

Reference Values for Confirmation Items

ITEMS Measrrnment methed

Wow & flutter Test tape When the test tape TCC-112 (3000Hz) has been 0.25% or

Measurement Standard Adjusting]

conditions Values positions

:TCC-112(3000Hz) played back with the recording and playback less

mecganism at the beginning of forward (WRMS)

Measurement outut winding, the frequency counter reading of

terminal wow & flutter should be 0.25% or less

:Headphone terminal (WRMS).

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