LG SB74 Service Manual Download

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2. SMPS P.C. BOARD DIAGRAM

NOTE: Warning

Parts that are shaded are critical With
respect to risk of fire or electrical shock.

3-33

3-34

Summary of Contents for SB74

Page 1: ...NUAL Stylish Powerful Portable Boom Box SERVICE MANUAL CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL MODEL SB74 Website http biz lgservice com Internal Use Only SEPTEMBER 2009 P NO AFN73250927 ...

Page 2: ...DED VIEWS CABINET AND MAIN FRAME SECTION SB74 2 1 PACKING ACCESSORY SECTION 2 5 SECTION 3 ELECTRICAL PART TROUBLESHOOTING GUIDE 3 1 WAVEFORMS OF MAJOR CHECK POINT 3 9 WIRING DIAGRAM 3 14 BLOCK DIAGRAMS 3 15 CIRCUIT DIAGRAMS 3 17 CIRCUIT VOLTAGE CHART 3 27 PRINTED CIRCUIT DIARGAMS 3 29 SECTION 4 REPLACEMENT PARTS LIST 4 1 CONTENTS ...

Page 3: ...ser beams may damage the eyes Absolutely never permit laser beams to enter the eyes Also NEVER switch ON the power to the laser output part lens etc of the pick up if it is damaged 5 Cleaning the lens surface If there is dust on the lens surface the dust should be cleaned away by using an air bush such as used for camera lens The lens is held by a delicate spring When cleaning the lens surface the...

Page 4: ...re replacing a component part first disconnect the power supply lead wire from the unit 2 All equipment measuring instruments and tools must be grounded 3 The workbench should be covered with a conductive sheet and grounded When removing the laser pick up from its conductive bag do not place the pick up on the bag This is because there is the possibility of damage by static electricity 4 To preven...

Page 5: ... 5 Do not use freon propelled chemicals These can generate electrical charges sufficient to damage ESD devices 6 Do not remove a replacement ESD device from its protective package until immediately before you are ready to install it Most replacement ESD devices are packaged with leads electrically shorted together by conductive foam aluminum foil or comparable conductive materials 7 Immediately be...

Page 6: ...SB74_VXX mcs 2 Insert the USB flash into the USB host 3 Set Function to the USB position Appear onto the LCD CHECKING UPGRADE SUCCESS 4 After finish Un plug the AC inlet about 2sec Than connect the AC inlet source again 5 Software upgrade completed 6 You can check the software version 7 At Power on mode Press STOP button of the set and PLAY key of the RCU together LCD shows SB74_VXX version ...

Page 7: ...7 5 108MHz Intermediate Frequency 128KHz Oscillator frequency 32 768KHz Frequency response Audio 100 Hz 10 KHz AMPLIFIER PORTABLE IN Out put Power 7 5 W 7 5 W In put sense 500 mV Frequency response Audio 100 Hz 18 KHz Signal to Noise Ratio More than 55dB SPEAKER Model G C40 55 8F 10W Type 1 Way 1 Speaker Impedance 8 Ω Rfrequency Response 120 Hz 20 KHz Rated Input Power 8 W Max Input Power 10 W Net...

Page 8: ...59R CABLE1 CABLE4 279R 279L A26 280 300 277A 277B 276 275R 275L 274L 274R CABLE3 CABLE2 BELT1 277C 458 461 463 456 462 456 462 451 460 460 451 458 458 451 451 451 460 FRONT USB CABINET AND MAIN FRAME SECTION SB74 NOTES THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE LITERATURE SECTION 2 EXPLO...

Page 9: ...2 3 2 4 ...

Page 10: ...2 5 PACKING ACCESSORY SECTION Remote Control 900 Battery 808 Instruction Ass y 801 Packing 803 Box 802 Packing 803 Bag 804 ...

Page 11: ...2 6 ...

Page 12: ...of Main PCB is short 12V NO Is the D911 nomal Is Vcc 9V 25V supplied to IC911 pin5 YES Check or replace the D911 NO Replace the D952 Is the D952 nomal YES NO Replace the D950 Is the D950 nomal YES NO 2 P SENS PART Check U301A Does 4V appear at U301A YES Is the D702 nomal Check JK600 pin21 YES Replace the D702 Check IC603 pin58 SECTION 3 ELECTRICAL PART Check D306 Refer SMPS 12V Check NO NO NO NO N...

Page 13: ...place Q206 Q208 Check R635 4 AUDIO ABNORMAL NO YES YES Check the connection of speakers NO Check the High of U200 pin7 NO Check the function input Check the output of U200 pin1 2 14 15 Check the input signal of U200 pin4 12 Check the DC 12V of U200 pin3 13 YES NO Normal Check the FB302 Check the Power Circuit YES NO Check the IC603 pin81 HIGH or LOW YES Replace IC603 ...

Page 14: ... 23 YES PORTABLE Check the input signal of U503 pin7 8 NO Check the input signal CN500 NO Check L800 L802 NO Check R800 R801 YES Check the output signal of U503 pin19 23 NO Check C810 C811 YES TUNER Check the input signal of U503 pin1 2 NO Check the output signal of U101 pin5 6 NO Check the output signal of C102 C103 NO Check the output signal of R100 R101 YES Check the output signal of U503 pin19...

Page 15: ...02 Reset circuit When power supply to IC603 pin107 Low High OK YES NO NO NO NO U302 3 3V output normal YES OK Replace ZD302 Check Q308 output normal YES Check ZD302 normal YES Check R308 YES NO Replace R308 OK Check D301 YES NO Replace D301 Check R328 YES NO Replace R328 Check Q302 output 12V YES Check ECO POWER is HIHGT YES NO NO Check or replace R305 R303 Q301 OK Check F301 YES NO Replace F301 N...

Page 16: ...IC604 pin13 is 3 3V NO YES Check or replace X601 Check IC600 pin1 6 X601 operation NO OK 9 U654 ABNORMAL NO Check U654 pin1 CE pin6 SCK YES Check U654 pin2 5 SO SI YES NO Replace U654 OK NO Refer to 3 3V troubleshooting Check U654 pin8 VDD 3 3V YES OK 10 IC601 ABNORMAL NO Check IC601 pin34 CLK pin35 CKE YES Check MCU IC603 YES NO Replace MCU OK NO Refer to MCU troubleshooting Check MCU IC603 volta...

Page 17: ...heck the control function NO OK 12 U501 ABNORMAL NO YES Refer to power supply U302 3 3V LCD display check Check the power supply to U501 pin7 YES NO Check MICOM U603 pin71 CS pin72 DAT pin73 WR Check U501 pin1 CS pin3 WR pin4 data YES NO Replace MICOM YES OK 13 U101 FM TUNER MODULE YES Check Q305 B High Check the power supply of U101 pin3 NO YES Check JK600 pin24 26 Check TU SCL TU SDA NO YES OK C...

Page 18: ... 0V NO NO NO NO 15 CD READING CHECK NO YES Check CN723 pin6 7 SL SL Check Connector locking CN703 CN723 Does sled motor move YES NO Does the laser move YES NO Defective pickup or U703 U704 YES NO Defective pickup or U703 U704 Check CN703 pin1 2 F F YES NO Does laser light YES NO Defective pickup or Q701 Check CN703 pin19 LD YES NO Does the spindle motor rotate YES NO Defective pickup or U703 U704 ...

Page 19: ...705 NO NO NO Check reading YES Check CN705 pin3 4 D D Check CN401 pin2_5V NO NO Playing Check audio output YES Check U503 pin3 4 Check U703 pin55 57 YES NO NO Check SMPS power supply NO Check Power supply circuit Q308 Check Power supply circuit Q302 Check F301 YES Replace Q308 YES Replace Q302 YES Replace F301 NO Check MICOM IC603 pin116 117 D D ...

Page 20: ...VE AND MOTOR WAVEFORM WAVEFORMS OF MAJOR CHECK POINT SL SL SP SP U704 pin19 1 U704 pin20 2 U704 pin22 3 U704 pin21 4 TE EE FE SP U703 pin62 5 U703 pin61 6 U703 pin60 7 U704 pin21 8 2 WHEN CD PLAYING FE EE TE SP WAVEFORM ...

Page 21: ...3 10 3 WHEN CD SEARCHING EE TE FE WAVEFORM EE TE FE U703 pin61 9 U703 pin62 10 U703 pin60 11 TD FD U703 pin14 12 U703 pin13 13 4 WHEN CD PLAYING FD TD WAVEFORM ...

Page 22: ...STOP ACTION SLE SP T F WAVEFORM Sp SLE TE FE U704 pin21 14 U704 pin20 15 U704 pin4 16 U704 pin2 17 MCK DIN RW BUSY U703 pin41 18 U703 pin19 19 U703 pin20 20 U703 pin21 21 6 CD READING CD MCK DIN RW BUSY WAVEFORM ...

Page 23: ...3 12 7 WHEN CD PLAYING RF WAVEFORM U703 pin63 22 LRCK BCK MCK DATA U703 pin39 23 U703 pin40 24 U703 pin41 25 U703 pin38 26 8 CD READING DAC LRCK BCK MCK DATA WAVEFORM ...

Page 24: ...3 13 9 WHEN USB OPERATING D 5V D WAVEFORM D 5V D CN705 pin4 27 CN705 pin2 28 CN705 pin3 29 SDIO RST SCK U101 pin2 30 U101 pin8 31 U101 pin1 32 10 RADIO OPERATING TU DA CLK RST WAVEFORM ...

Page 25: ...3 14 WIRING DIAGRAM JK500 3P 13P CN501 CON2 2P SPK 2P 5P 8P 5P 3P CN580 24P 9P ...

Page 26: ...3 15 BLOCK DIAGRAM ...

Page 27: ...3 16 ...

Page 28: ...AL DESIGN BE MODIFIED OR ALTERED WITH OUT PERMISSION FROM THE LG CORPORATION ALL COMPONENTS SHOULD BE REPLACED ONLY WITH TYPES IDENTICAL TO THOSE IN THE ORIGINAL CIRCUIT SPECIAL COMPONENTS ARE SHADED ON THE SCHEMATIC FOR EASY IDENTIFICATION THIS CIRCUIT DIAGRAM MAY OCCASIONALLY DIFFER FROM THE ACTUAL CIRCUIT USED THIS WAY IMPLEMENTATION OF THE LATEST SAFETY AND PERFORMANCE IMPROVEMENT CHANGES INTO...

Page 29: ...A 1 2 3 4 5 6 7 8 9 10 11 12 B C D E F G H I J K L M N O P Q R S T MAIN SB74 2009 07 10 30 31 32 2 MAIN CIRCUIT DIAGRAM 3 19 3 20 WAVEFORM ...

Page 30: ... 1 2 3 4 5 6 7 8 9 10 11 12 B C D E F G H I J K L M N O P Q R S T CD SB74 2009 07 10 1 16 17 2 15 3 4 8 14 5 22 10 6 9 7 11 12 13 18 25 24 23 26 19 20 21 27 28 29 WAVEFORM 3 22 3 CD CIRCUIT DIAGRAM 3 21 ...

Page 31: ...A 1 2 3 4 5 6 7 8 9 10 11 12 B C D E F G H I J K L M N O P Q R S T MCU9800 SB74 2009 07 10 3 23 3 24 4 MCU9800 CIRCUIT DIAGRAM ...

Page 32: ...A 1 2 3 4 5 6 7 8 9 10 11 12 B C D E F G H I J K L M N O P Q R S T LCD USB PH SB74 2009 07 10 3 25 3 26 5 LCD USB PH CIRCUIT DIAGRAM ...

Page 33: ...ND 119 DGND 120 1 20V 121 DGND 122 1 20V 123 DGND 124 1 2 125 1 85 126 0 3 127 1 5 128 3 24 IC604 1 0 02 2 0 02 3 0 05 4 DGND 5 3 3 6 0 03 7 DGND 8 3 28 9 DGND 10 0 04 11 GND 12 0 06 13 3 25 14 AGND 15 0 19 16 0 19 17 0 04 18 0 19 19 0 19 20 0 04 IC605 1 GND 2 3 31 3 1 2 IC654 1 3 25 2 0 01 3 2 12 4 DGND 5 1 31 6 2 68 7 2 12 8 3 25 U200 1 7 74 2 7 75 3 15 52 4 1 49 5 NC 6 7 78 7 7 45 8 GND 9 GND 1...

Page 34: ...PRINTED CIRCUIT BOARD DIARGAMS 1 1 MAIN P C BOARD DIAGRAM TOP VIEW 3 29 3 30 ...

Page 35: ...1 2 MAIN P C BOARD DIAGRAM BOTTOM VIEW 3 31 3 32 ...

Page 36: ...2 SMPS P C BOARD DIAGRAM NOTE Warning Parts that are shaded are critical With respect to risk of fire or electrical shock 3 33 3 34 ...

Page 37: ...3 1 MCU9800 P C BOARD DIAGRAM TOP VIEW 3 35 3 36 ...

Page 38: ...3 2 MCU9800 P C BOARD DIAGRAM BOTTOM VIEW 3 37 3 38 ...

Page 39: ...4 FRONT P C BOARD DIAGRAM 5 CD JACK P C BOARD DIAGRAM 3 39 3 40 ...

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