LG CM2760, Service Manual

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SECTION 3
ELECTRICAL
CONTENTS
ONE POINT REPAIR GUIDE ............................................................................................................................ 3-2
1. NO POWER PROBLEM ......................................................................................................................... 3-2
2. SPEAKER NO AUDIO OUTPUT ............................................................................................................ 3-3
3. USB NO DETECT ................................................................................................................................... 3-4
4. PROTECTION ......................................................................................................................................... 3-5
ELECTRICAL TROUBLESHOOTING GUIDE OF AUDIO PART ..................................................................... 3-8
1. SMPS POWER CIRCUIT ........................................................................................................................ 3-8
2. FLD DISPLAY CHECK ......................................................................................................................... 3-10
3. TOUCH PAD CHECK ........................................................................................................................... 3-11
4. PWM MODULATION PART .................................................................................................................. 3-12
5. POWER AMP PART CHECK ............................................................................................................... 3-13
6. AUX FUNCTION CHECK ..................................................................................................................... 3-14
7. TUNER FUNCTION CHECK................................................................................................................. 3-15
ELECTRICAL TROUBLESHOOTING GUIDE OF CD PART ......................................................................... 3-16
1. CD PART .............................................................................................................................................. 3-16
2. OPEN/ CLOSE NG ............................................................................................................................... 3-17
3. “ READING ” DISPLAY CHECK (= ONLY “CD” DISPLAY) .................................................................. 3-17
4. READING OK CHECK (= “NO DISC” DISPLAY) ................................................................................. 3-18
5. USB PART ............................................................................................................................................ 3-22
WAVEFORMS OF MAJOR CHECK POINT .................................................................................................... 3-23
WIRING DIAGRAM .......................................................................................................................................... 3-29
BLOCK DIAGRAM .......................................................................................................................................... 3-31
CIRCUIT DIAGRAMS ...................................................................................................................................... 3-33
1. MAIN - SMPS CIRCUIT DIAGRAM ...................................................................................................... 3-33
2. MAIN - CD CIRCUIT ............................................................................................................................. 3-35
3. MAIN - DSP CIRCUIT DIAGRAM ......................................................................................................... 3-37
4. MAIN - AMP/ TUNER CIRCUIT DIAGRAM .......................................................................................... 3-39
5. MAIN - POWER CIRCUIT DIAGRAM ................................................................................................... 3-41
6. TOUCH CIRCUIT DIAGRAM ................................................................................................................ 3-43
7. VFD/ USB/ PORTABLE CIRCUIT DIAGRAM ....................................................................................... 3-45
CIRCUIT VOLTAGE CHART ........................................................................................................................... 3-47
1. CONNECTORS VOLTAGE ................................................................................................................... 3-47
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-49
1. MAIN P. C. BOARD .............................................................................................................................. 3-49
2. TOUCH P. C. BOARD .......................................................................................................................... 3-51
3. VFD P. C. BOARD ................................................................................................................................ 3-51
4. USB P. C. BOARD ................................................................................................................................ 3-53
5. PORTABLE P. C. BOARD .................................................................................................................... 3-53
3-1