SAMSUNG SCM7270LC Service Manual

MUSIC CENTER

SCM-7270

SERVICE

Manual

MUSIC CENTER CONTENTS

1. Precautions

2. Specifications

3. Disassembly and Reassembly

4. Alignment and Adjustments

5. Special Circuit Descriptions

6. Troubleshooting

7. Exploded Views and Parts List

8. Electrical Parts List

9. Block Diagrams

10. PCB Diagrams

11. Wiring Diagram

12. Schematic Diagrams

MONO/ST

CLOCK

TIMER

TUNING

TUNER

TAPE

PHONO

VOLUME

BAND

PRESET/MANUAL

MEMORY

CLASSIC POPS ROCK

EQ PRESET

PLAY/PAUSE

STOP/CLEAR

HI-SPEED DUBBING

OPEN/CLOSE

DISPLAY

INTRO

SKIP

REPEAT

RANDOM

ON/STANORY

POWER

DECK 1

REC/PLAY

PLAYBACK

DECK 2

HIGH SPEED DUBBING CONTINUOUS PLAY

PHONES

REC PLAY REW STOP/EJ PAUSEF.FWD PLAY REW F.FWD STOP/EJ PAUSE

1. Precautions

Follow these safety, servicing and ESD precautions to prevent damage and protect against potential hazards such as electrical shock and X-rays.

1-1 Safety Precautions

1. Be sure that all of the built-in protective devices are replaced.

(Reading should

2. When reinstalling the chassis and its assemblies, be sure to restore all protective devices, including control knobs and compartment covers.

3. Make sure that there are no cabinet openings through which people-particularly children--might insert fingers and contact dangerous voltages. Such openings include the spacing between the picture tube and the cabinet mask, excessively wide cabinet ventilation slots, and improperly fitted back covers.

Device Under

Test

Test all

exposed metal

surfaces

2-Wire Cord

Also test with plug reversed (using AC adapter plug as required)

Fig. 1-1 AC Leakage Test

not be above

0.5mA)

Leakage Currant Tester

Earth Ground

4. Design Alteration Warning: Never alter or add to the mechanical or electrical design of the unit. Example: Do not add auxiliary audio or video connectors. Such alterations might create a safety hazard. Also, any design changes or additions will void the manufacturer's warranty.

5. Leakage Current Hot Check (Figure 1-1): Warning: Do not use an isolation transformer during this test. Use a leakagecurrent tester or a metering system that complies with American National Standards Institute (ANSI C101.1, Leakage Current for Appliances), and Underwriters Laboratories (UL Publication UL1410, 59.7).

With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. With the unit's AC switch first in the ON position and then OFF, measure the current between a known earth ground (metal water pipe, etc.) and all exposed metal parts. Examples: Handle brackets, metal cabinets, screwheads and control shafts. The current measured should not exceed 0.5 milliamp. Reverse the powerplug prongs in the AC outlet and repeat.

6. Insulation Resistance Cold Check: (1) With the unit's AC plug disconnected from the AC source, connect an electrical jumper across the two AC prongs. (2) Set the power switch to ON. (3) Measure the resistance between the shorted AC plug and any exposed metallic parts. Example: Screwheads, antenna, control shafts or handle brackets.

If any of the exposed metallic parts has a return path to the chassis, the measured resistance should be between 1 and 5.2 megohms. If there is no return path, the measured resistance should be "infinite." If the resistance is outside these limits, a shock hazard might exist. See Figure 1-2

Antenna Terminal

Exposed Metal Part

ohm

Ohmmeter

Fig. 1-2 Insulation Resistance Test

Samsung Electronics 1-1

Precautions

1-1 Safety Precautions (Continued)

7. Components, parts and wiring that appear to have overheated or that are otherwise

damaged should be replaced with parts that meet the original specifications. Always determine the cause of damage or overheating, and correct any potential hazards

8. Observe the original lead dress, especially

near the following areas: Antenna wiring, sharp edges, and especially the AC and high voltage power supplies. Always inspect for pinched, out-of-place, or frayed wiring. Do not change the spacing between components and the printed circuit board. Check the AC power cord for damage. Make sure that no wires or components touch thermally hot parts.

1-2 Servicing Precautions

9. Product Safety Notice: Some electrical and mechanical parts

have special safety-related characteristics which might not be obvious from visual inspection. These safety features and the protection they give might be lost if the replacement component differs from the original--even if the replacement is rated for higher voltage, wattage, etc.

10 Components that are critical for safety are

indicated in the circuit diagram by

shading, or . Use replacement

components that have the same ratings,

especially for flame resistance and

dielectric strength specifications. A

replacement part that does not have the

same safety characteristics as the original

might create shock, fire or other hazards.

Warning1: First read the "Safety Precautions" section of this manual. If some unforeseen circumstance creates a conflict

between the servicing and safety precautions, always follow the safety precautions.

1. Servicing precautions are printed on the cabinet. Follow them.

2. Always unplug the unit's AC power cord from the AC power source before attempting to: (a) Remove or reinstall any component or assembly, (b) Disconnect an electrical plug or connector, (c) Connect a test component in parallel with an electrolytic capacitor.

3. Some components are raised above the printed circuit board for safety. An insulation tube or tape is sometimes used. The internal wiring may be clamped to prevent contact with thermally hot components. Reinstall all such elements to their original position.

4. After servicing, always check that the screws, components and wiring have been correctly reinstalled. Make sure that the portion around the serviced part has not been damaged.

5. Check the insulation between the blades of the AC plug and accessible conductive parts (examples: metal panels, input terminals and earphone jacks).

6. Insulation Checking Procedure: Disconnect the power cord from the AC source and turn the power switch ON. Connect an insulation resistance meter (500V) to the blades of the AC plug.

The insulation resistance between each blade of the AC plug and accessible conductive parts (see above) should be greater than 1 megohm.

7. Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit (or any of its assemblies) unless all solid-state heat sinks are correctly installed.

8. Always connect a test instrument's ground lead to the instrument chassis ground before connecting the positive lead; always remove the instrument's ground lead last.

Samsung Electronics1-2

1-3 Precautions for Electrostatically Sensitive Devices (ESDs)

Precautions

1. Some semiconductor ("solid state") devices are easily damaged by static electricity. Such components are called Electrostatically Sensitive Devices (ESDs). Examples include integrated circuits and some field-effect transistors. The following techniques will reduce the occurrence of component damage caused by static electricity.

2. Immediately before handling any semiconductor components or assemblies, drain the electrostatic charge from your body by touching a known earth ground. Alternatively, wear a discharging wrist-strap device. (Be sure to remove it prior to applying power--this is an electric shock precaution.)

3. After removing an ESD-equipped assembly, place it on a conductive surface such as aluminum foil to prevent accumulation of electrostatic charge.

4. Do not use freon-propelled chemicals. These can generate electrical charges that damage ESDs.

5. Use only a grounded-tip soldering iron when soldering or unsoldering ESDs.

6. Use only an anti-static solder removal device. Many solder removal devices are not rated as "anti-static" (these can accumulate sufficient electrical charge to damage ESDs).

7. Do not remove a replacement ESD from its protective package until you are ready to install it. Most replacement ESDs are packaged with leads that are electrically shorted together by conductive foam, aluminum foil or other conductive materials.

8. Immediately before removing the protective material from the leads of a replacement ESD, touch the protective material to the chassis or circuit assembly into which the device will be installed.

9. Minimize body motions when handing unpackaged replacement ESDs. Motions such as brushing clothes together, or lifting a foot from a carpeted floor can generate enough static electricity to damage an ESD.

1-4 Special Precautions and Warning Labels for Laser Products

(UL)

This Product Complies with DHHS Rules 21CFR, Sub chapter J.At date of Manufacture

(SCAN)

CAUTION : INVISIBLE LASER RADIATION WHEN OPEN

AND INTERLOCKS DEFEATEO AVOIDEXPOSURE TO BEAM

ADVARSEL:USYNLIG LASERSTRÅLING VED ABNING

NÅR SIKKERHEDSAFBRYDERE ER UDE AF FUNKTION

UNDGA UDSAETTELSE FOR STRALING

VARO:AVATTAESSA JA SUOJALUKITUS OHITETTAESSA

OLET ALTTINA NAKYMATTÖMALLE LASERSATEILYLLE ALA KATSO SATEESEEN!

VARNING:OSYNLIG LASERSTRÅLNING NAR DENNA DEL

AR OPPNAD OCH SPARREN AR URKOPPLAD BETRAKTA EJSTRÅLEN!

CERTIFIED ONLY TO CANADIAN ELECTRICAL CODE.

CERTIFIE EN VERTU DU CODE CANADIAN DE LELETRICITE SEULEMENT

Fig. 1-3 Warning Labels (Location: Enclosure Block)

(EU)

(CSA)

UL : Manufactured for U.S.A. Market. CSA : Manufactured for Canadian Market. EU : Manufactured for European Market. SCAN : Manufactured for Scandinavian

Market.

(EU)

CLASS 1 LASER PRODUCT

Fig. 1-4 Warning Labels (Location: Disc Clamper, Inner Side of Unit Door or Nearby Unit Chassis )

Samsung Electronics 1-3

Precautions

1-4 Special Precautions and Warning Labels for Laser Products (Continued)

1-4-1 Warnings

1. When servicing, do not approach the LASER exit with the eye too closely. In case it is necessary to confirm LASER beam emission, be sure to observe from a distance of more than 30 cm from the surface of the objective lens on the optical pick-up block.

2. Do not attempt to handle the objective lens when the DISC is not on the tray.

1-4-2 Laser Diode Specifications

Material: GaAs+ GaAlAs Wavelength: 760-800 nm Emission Duration: Continuous

Laser Output: 0.2 mw (measured at a

1.6 mm distance from the objective lens surface on the optical pick-up block.)

1-4-3 Handling the Optical Pick-up

1. Static electricity from clothing or the body may cause electrostatic breakdown of the laser diode in the Optical Pickup. Follow this procedure:

2. Place a conductive sheet on the work bench (i.e., the black sheet used for wrapping

repair parts.) Note: The surface of the work

bench should be covered by a copper

ground plane, which is grounded.

3. The repair technician must wear a wrist strap which is grounded to the copper sheet.

4. To remove the Optical Pickup block: Place the set on the conductive sheet, and momentarily touch the conductive sheet

with both hands. (While working, do not

allow any electrostatic sources--such as clothes--to touch the unit.)

5. Ground the "Short Terminal" (located on the PCB, inside the Pickup Assembly) before replacing the Pickup. This terminal should be shorted whenever the Pickup Assembly

is lifted or moved.

short terminal

SOH91VI(LDP)

short terminal

SOH91CI(CAR,walkman)

6. After replacing the Pickup, reopen the Short Terminal. See diagrams below:

THE UNIT

(1) WRIST-STRAP FOR GROUNDING

short terminal

SOH-A1

(CMS-V10,CMS-V30)

SOH94T4N

(CMS-V10,CMS-V30)

CONDUCTIVE SHEET

short terminal

Samsung Electronics1-4

2. Product Specfications

Samsung Electronics

2-1

General

Amp

Cassette

Tuner

Compact Disc

Power source Power consumption Dimensions (mm)

Power output Total harmonic distortion Frequency range Signal to noise ratio Channel separation Input sensitivity (PHONO)

Frequency range Usable sensitivity Signal to noise ratio IF rejection ratio Total harmonic distoration Separation (Stereo)

Frequency range Usable sensitivity Signal to noise ratio IF rejection ratio Total harmonic distortion

Frequency range Usable sensitivity Signal to noise ratio

Frequency range WOW FLUTTER Erasing effect (W/Filter) Signal to noise ratio Total harmonic distortion

Frequency response Signal to noise ratio Channel separation Total harmonic distortion

125Hz ~ 8KHz

0.35% 60 dB 40 dB 5%

100Hz ~ 10KHz(±1dB) 85 dB(1kHz 0dB) 75 dB(1kHz 0dB)

0.1%(1kHz 0dB)

87.5 ~ 108MHz 15 dB 55 dB 60 dB

1.5% 25 dB

522 ~ 1611KHz 54 dB 40 dB 30 dB 2%

146 ~ 290KHz 60 dB 35 dB

10W

0.5% 50Hz ~ 17kHz 60 dB 45 dB 400mV

AC 230V 50HZ 62 W 350(W) x 328(H) x 316(D)

* Specifications are subject to change without notice.

Samsung Electronics

Remote Control Exploded View

2-2

EQ PRESET MUTE

MONO/ST

PHONO

POWER

PLAY/PAUSE

VOLUME

TUNING

INTRO

MEMORY BAND

SLEEP PRESET/MANUAL

CLOCK TIMER

TUNER

SKIP/SEARCH STOP

REPEATDISPLAYPROGRAM

TAPE CD

VOLUME

3. Disassembly and Reassembly

3-1 Turn-Table, Cabinet-Front , Cabinet-Bottom

1. Remove Door-CD (Direction A).

2. Release 6 screws !.

3. Remove Turn-Table (Direction B).

4. Release 2 screws @.

5. Release 2 screws #.

6. Remove Front-Cabinet.



Figure 3-1

Samsung Electronics 3-1

Figure 3-2

3-2 Samsung Electronics

3-2 Deck-CD, Front-PCB, Cassette-Deck, Door-Cassette

Disassembly and Reassembly

1. Release 2 screws !.

2. Remove Deck-CD AssÕy.

3. Release 4 screws @.

4. Remove Deck-CD.

5. Release 17 screws #.

6. Remove Front-PCB, SUB-PCB.

7. Release 7 screws $.

8. Remove Cassette-Deck.

3-3 Cabinet-Bottom and Main-PCB

1. Release 3 screws !.

2. Remove the Main-PCB .

Figure 3-3

Samsung Electronics 3-3

Disassembly and Reassembly

Figure 3-4

3-4 CD Pack

3-4 Samsung Electronics

Disassembly and Reassembly

1. Undo 2 screws (A), and remove the Chuck-Bracket @, the Ferrite-Magnet 5, Chuck Union-Table $ and Chunk-Holder &.

2. Undo 2 screws(B), pull the Tray-M1 1 forward to remove.

3. Undo 1 screw(C), and remove the Cam-Spring 8 and the Cam #.

4. Undo 1 screw(D), and remove the Gear-Pulley ( the Belt-Pulley @, the Gear-A % and the Gear-B ^.

5. Undo 2 screws(E), and remove the Motor-Pulley ) and the Dc-Motor 0.

6. Undo 2 screws(F), and remove the Leaf-Switch 9 and the Detector-Switch “.

Disconnect the Lead-Connector assÕy 4 with soldering iron.

7. Remove the AssÕy PCB 3 with soldering iron and remove the PCB-Holder +.

8. Undo 4 screws from the CD-Shaft 7, and remove the CD-Rubber 6 and the CD-Deck ‘.

Figure 3-5

Samsung Electronics 3-5

3-5 CD Deck

1. Remove the Shaft !.

2. Lift the P/U @.

Note : Do not to touch the surface of lens.

3. Lift the Center-ring #.

4. Remove the Spring-T/Table $.

5. Remove the Turn-Table (M) %.

6. Remove 2 screws ^ and then remove the Spindle-Motor &.

7. Remove the Cover-Gear * by pushing the hook.

8. Remove the Gear (c) ( by pushing the hook.

9. Lift the Gear(b) ).

10. Remove the Gear(a) 1.

11. Remove 2 screws 2 and the then remove the Feed-Motor 3.

12. Remove the Chassis-Deck (M) 4.

Disassembly and Reassembly

4. Alignment and Adjustments

4-1 Tuner

Samsung Electronics 4-1

FM THD Adjustment

Minimum Distortion (Figure 4-1)

SSG FREQ. Adjustment

point

(IT1)

98 MHz

FM DETECTOR COIL

FM Search Level Adjustment

Adjust ISVR1 so that “TUNED” of LCD is lighted (Figure 4-2)

Figure 4-2 FM Auto Search Level Adjustment

Figure 4-3 FM Stereo Separation Adjustment

Figure 4-1 IF CENTER and THD Adjustment

SSG FREQ. Adjustment

point

(ISVR1)

98 MHz

SEMI-VR(50KΩ)

FM Seperation Adjustment

L-CH/R-CH : Maximum (Figure 4-3)

SSG FREQ. Adjustment

point

(ISVR2)

98 MHz

SEMI-VR(5KΩ)

FM SSG

GND

30 dB

FM SSG

Output GND

Speaker Terminal

FM Antenna Terminal

Distortion Meter

Input

SET

Input

output

Oscilloscope

Speaker terminal

FM antenna

OUT

GND

VTVM

SET

EXT

FM SSG

Stereo Modulator (Pilot 10%)

75Ω

50Ω

Dummy

FM IN

FM Antenna

SET

50 KΩ

5 KΩ

CSVR801

CCON801

ISVR2

ISVR1

IT2

OT1

OT2

OCT2

OCT4

OCT3

OL2

OL1

TCON1

OCT1

IT1

KT431

1. AM Standard Signal Generator (S. S. G) : 400Hz, 30% MOD

2. Oscilloscope

3. VTVM

4. Frequency counter

5. Loop antenna

6. Dummy load (4½)

7. DC voltmeter

1. Check the source voltage.

2. Set function and band switches to the band to be aligned.

3. Set the equalizer, volume and balance controls to mid position

4-2 Samsung Electronics

4-1-1 Test Equipment

4-1-2 Pre-Adjustment

Alignment and Adjustments

Intermediate frequency(IF) adjustment

Figure 4-5

522 KHz

IT2

OT1

0.9V

9VOCT2

OCT1

OL1

1611 KHz

594 KHz

1404 KHz

Maximum output

Remark

Adjsut. Point

FREQ.Setting

SSG.FREQ.

Item

Step

Pre-Setup Condition

Figure 4-4 Connect DC voltmeter to TCON1 and GND(TP1)

AM tracking adjustment

522 KHz

594 KHz

1404 KHz

AM Signal Generator

Test Loop Antenna

Speaker terminal

VTVM

AM Loop Antenna Jack

SET

TP2

TP1

Input

DC Voltmeter

SET

60 cm

GND

Oscilloscope

OUT

AM frequency coverage adjustment

Repeat step 2 and 3 serveral times

Repeat step 5 and 6 serveral times

Figure 4-4 AM Frequency Coverage Adjustment

Figure 4-5 AM Tracking Adjustment

Samsung Electronics 4-3

Alignment and Adjustments

4-2 Cassette Deck

4-2-1 Additional Test Equipment : Testing Tape

4-2-2 Recording Bias Adjustment

Tape speed (normal speed) adjustment

Figure 4-6

CSVR801

3 KHz

Figure 4-7

To Adjust

Remarks

Pre-Setup

Item

Pre-Setup Condition

Figure 4-8

Insert MTT-111 to Deck A or B Press PLAY button

Maximum output and identical phase of L,R channel. Set the screw after adjustment

Insert MTT-114 to Deck A and Deck B Press PLAY button

AZIMUTH (DECK A,B) adjustment

Speaker Terminal

SET

Frequency Counter

Figure 4-6

Figure 4-7

Recording /Play head

REVERSE PLAY

AZIMUTH control knob

Figure 4-8

In Out

Speaker Terminal

Oscilloscope

SET

(GND)

VTVM

V H

CSVR801

CCON801

ISVR2

ISVR1

IT2

OT1

OT2

OCT2

OCT4

OCT3

OL2

OL1

TCON1

OCT1

IT1

KT431

1. Connect frequency counter KC434 and press the REC button.

2. Adjust KT431(BIAS OSC COIL) until frequency counter reads 85 ±0.2KHz.

1. MTT-111(or equivalent) : Test tape on which 3 KHz signal is recorded.(Tape speed adjustment)

2. MTT-114(or equivalent) : Test tape on which 10 KHz signal is recorded. (Azimuth adjustment)

4-3 CD

Alignment and Adjustments

4-4 Samsung Electronics

4-3-1 To Adjust FOCUS BIAS (STOP mode)

1. Set Volt/Div of the oscilloscope to DC 100mV.

2. Ground the scope input and set the waveform to 0V, DC range.

3. Connect the GND terminal of the oscilloscope to Vref, and (+) terminal to center of TP1.

4. Set NVR1701 to 0mV.

4-3-2 To Adjust Tracking Gain (PLAY mode)

1. Connect the ground terminal of the oscilloscope to Vref and (+) terminal to TP2.

2. Load and play the disc.

3. While the disc is running, adjust the gain with NVR1704 as shown below.

4-3-3 To Adjust Focus Gain (PLAY mode)

1. Connect the ground terminal of the oscilloscope to Vref and (+) terminal to TP1.

2. Load and play the disc.

3. While the disc is running adjust the gain with NVR1703 as shown in the following figure.

4-3-4 To Adjust E/F Balance (PLAY mode)

1. Set Time/Div of the oscilloscope to 2mS.

2. Set Volt/Div of the oscilloscope to 0.5V.

3. Ground the scope input and set to DC, and then set the DC range.

4. Connect the ground terminal of the oscilloscope to Vref and (+)terminal to center to TP2.

5. Load and play the disc.

6. Turn NVR1704 counterclockwise to the minimum value.

7. Raise NVR1702 and adjust the waveform so that its middle comes to ground of the oscilloscope, (or until the upper half of waveform becomes symmetrical to the bottom half,A=B).

8. Adjust NVR1704(arrow) for normal sound.

TP2

TP1

Vref

NVR1704

NVR1703 NVR1702

NVR1701

TE CENTER

FE CENTER

E.F BAL

F.BIAS

Normal Frequency

VOLT/DIV : 0.2V TIME/DIV : 2mS

Low Frequency

High Frequency

A=B

Normal Frequency

VOLT/DIV : 0.1V TIME/DIV : 2mS

Low Frequency

High Frequency

100mV

250mV

100mV

6. Troubleshooting

6-1 Amplifier

6-1-1 Power Malfunction

Yes

LCD lamp is ON

Pins 73,31 of UIC1(LC72362) is at 5V

Voltages at RQ702,RQ703 are normal

Power Transistor & fuse normal

Connection

are soldering

of SCON1-FCW2

are normal

Voltages at RQ1, RQ2 and RFR1 are normal

Voltage at RQ701 is normal

Replace RQ701

Check Voltage at RIC1

Samsung Electronics 6-1

6-1-2 No Output

6-1-3 AM No Sound

Yes

Voltages at

IIC1(LC1851N) and semi conductors tuner section are normal

TCON1 is at

1.5V±1.5 on low coverage

7.5V±0.5 on high coverage

Voltage at FET are normal

Voltage at power supply section

Check pump charge circuitry(OQ5) connection or soldering of SCON1, FCW2, FCON1 soldering of pin77 of LC72362

Replace FET

Yes

Check pump charge circuitry (OQ5) connection of SCON1, FCW2, FCON1 soldering of pin77 of LC72362N

Yes

Voltage

at LC1851N(IIC1) and tuner semi conductors are normal (Refer to Schematic Diagram)

Voltage between TCON1: AM(MW) Low coverage 0.9V ±0.5 High coverage 9V ± 0.5 LW Low coverage 0.7 V ±0.5

High coverage

4.5V ± 0.5

Check loop antenna soldering and connection of OL1, OL2, OT1,OT2, IT2

Check voltage at power supply section

6-2 Samsung Electronics

Troubleshooting

6-1-4 Tape Not Playing

6-1-5 Audio Output Problem

Yes

Connection and soldering of head wire normal

Replace JIC1 (KA22291)

Voltage at

JIC1(KA22291) are normal

(Refer to Schematic

Diagram)

Check power supply circuitry

Noise occurs at

pin3,22 or pin4,21 with volume

control at mid position

Noise occurs at pins1,24

Check function selector section

Yes

Speaker connections are normal

all pins of AIC1(LA4620)

are normal (Refer to Schematic

Diagram)

Voltage at base of AQ601,

AQ651(C945) is

less than

0.6V

Pattern & Speaker Jack normal

Check power supply section

Check Muting circuitry

Voltages to

Samsung Electronics 6-3

Troubleshooting

6-2-1 Malfunction of Disc Revolution

Check CLOSE S/W voltage.

CLOSE condition : 0V

Is Focus Search done properly ?

Check oscillation of NXF100 (16.9344MHz).

Does Laser function during

Focus Search ?

Replace PICK-UP.

Check NIC9282 pin73 voltage

Replace NIC9282.

Yes

POWER ON

Check CLOSE MOTOR driving

Replace NIC9220 or NIC9258.

element and CLOSE S/W.

during Focus Search : 5V

Yes

6-4 Samsung Electronics

Troubleshooting

6-2 CD

+ 45 hidden pages