LG MDV902 User manual

KARAOKE MINI
HOME THEATER
SERVICE MANUAL
MODEL : MDV902(MDS902V, MDS902S, MDS902W)
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
MODEL : MDV902(MDS902V, MDS902S, MDS902W)
SERVICE MANUAL
P/NO : AFN35036903 JULY, 2007
http://biz.lgservice.com

1-1
CONTENTS
SECTION 1
GENERAL
SERVICING PRECAUTIONS ......................................1-2
• NOTES REGARDING HANDLING OF THE PICK-UP
• NOTES REGARDING COMPACT DISC PLAYER REPAIRS
ESD PRECAUTIONS ...................................................1-4
LOCATION OF USERS CONTROLS.........................1-5
SPECIFICATIONS ........................................................1-7
SECTION 2
EXPLODED VIEWS
CABINET AND MAIN FRAME SECTION..................2-1
TAPE DECK MECHANISM EXPLODED VIEW ........2-3
1. TAPE DECK MECHANISM
(A/R & A/S : LEFT A/R DECK) ..........................2-3
2. TAPE DECK MECHANISM
(A/R & A/S : RIGHT A/S DECK).........................2-5
DVD MECHANISM EXPLODED VIEW ......................2-7
SPEAKER EXPLODED VIEW ....................................2-9
1. MODEL : MDS902V (FRONT SPEAKERS) ....2-9
2. MODEL : MDS902S (REAR SPEAKERS) .....2-11
3. MODEL : MDS902W (SUBWOOFER)...........2-13
PACKING ACCESSORY SECTION .........................2-17
SECTION 3
AUDIO PART ELECTRICAL
ELECTRICAL TROUBLESHOOTING GUIDE...........3-1
1. POWER (SMPS) ................................................3-1
2. P-SENS...............................................................3-2
3. VKK CHECK.......................................................3-2
4. MICOM (IC302) CHANGE.................................3-3
5. P-CTRL CHECK.................................................3-3
6. MUTING TROUBLESHOOTING (MUTE STATE) .......3-4
7. EXPEND IC (IC501 / 502) STATE ....................3-4
8. FUNCTION MODE HAS NO SOUND
(NJW1190) IC601................................................3-5
9. IC601 (NJW1190) TROUBLUSHOOTING .......3-9
10. AMP MODULE TROUBLESHOOTING..........3-10
11. REC CHECK
(Q201, Q202 ON : R276, R226 HIGH) ...........3-11
12. DUBBING CHECK
("NORMAL OR REC" // "HIGH") ......................3-12
INTERNAL BLOCK DIAGRAM OF ICs...................3-13
1. HA12237F.........................................................3-13
2. NJW1190 ..........................................................3-14
3. AF330W20FT ...................................................3-14
4. AF350W01FT ...................................................3-16
WIRING DIAGRAM ....................................................3-18
BLOCK DIAGRAM.....................................................3-20
SCHEMATIC DIAGRAMS .........................................3-22
1. SMPS (POWER) SCHEMATIC DIAGRAM ....3-22
2. SUB SMPS (POWER) SCHEMATIC DIAGRAM ....3-24
3. AUDIO MAIN SCHEMATIC DIAGRAM ..........3-26
4. DECK SCHEMATIC DIAGRAM ......................3-28
5. USB, AUX2 & HEADPHONE AMP
SCHEMATIC DIAGRAM .................................3-30
6. I/O JACK SCHEMATIC DIAGRAM.................3-32
7. AMP SCHEMATIC DIAGRAM.........................3-34
8. WOOFER AMP SCHEMATIC DIAGRAM ......3-36
9. FRONT SCHEMATIC DIAGRAM ...................3-38
PRINTED CIRCUIT DIAGRAMS...............................3-40
1. MAIN P.C.BOARD............................................3-40
2. SMPS (POWER) P.C.BOARD ........................3-44
3. SUB SMPS (POWER) P.C.BOARD ...............3-45
4. FRONT P.C.BOARD ........................................3-46
5. AMP P.C.BOARD .............................................3-50
6. WOOFER AMP P.C.BOARD ...........................3-52
SECTION 4
DVD PART ELECTRICAL
ELECTRICAL TROUBLESHOOTING GUIDE...........4-1
1. POWER...............................................................4-1
2. TEST & DEBUG .................................................4-2
3. USB .....................................................................4-7
WAVEFORMS ...............................................................4-8
1. WHEN POWER ON,
RESET & DATA ETC WAVEFORM ...................4-8
2.
OPEN / CLOSE WAVEFORM AT POWER ON
.......4-9
3.
STARTING ACTION WAVEFORM IN MD DEVICE ......4-9
4. FOCUS WAVEFORM (AT CD).........................4-10
5. FOCUS WAVEFORM (AT DVD) ......................4-10
6. AT POWER ON, SPINDLE SIGNAL AT MD DECK ........4-11
7. AT FIRST ACTION, FOCUS SIGNAL A, B, C, D ....4-11
8. TRACKING SIGNAL..........................................4-12
9. RF WAVEFORM ................................................4-12
10. DISK TYPE JUGEMENT WAVEFORM...........4-13
SCHEMATIC DIAGRAMS .........................................4-15
1. MPEG SCHEMATIC DIAGRAM .....................4-15
2. SERVO SCHEMATIC DIAGRAM ...................4-17
3. USB SCHEMATIC DIAGRAM.........................4-19
4. INTERFACE SCHEMATIC DIAGRAM ...........4-21
PRINTED CIRCUIT DIAGRAM .................................4-23
DVD P.C.BOARD .................................................4-23
SECTION 5
REPLACEMENT PARTS LIST ........5-1

1-2
NOTES REGARDING HANDLING OF THE PICK-UP
1. Notes for transport and storage
1) The pick-up should always be left in its conductive bag until immediately prior to use.
2) The pick-up should never be subjected to external pressure or impact.
2. Repair notes
1) The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.
2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and
impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or
damage to the printed-circuit board.
3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason
the adjustment point and installation screws should absolutely never be touched.
4) Laser 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, therefore, a cotton
swab should be used, taking care not to distort this.
6) Never attempt to disassemble the pick-up.
Spring by excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab. (Do not
use any other liquid cleaners, because they will damage the lens.) Take care not to use too much of this
alcohol on the swab, and do not allow the alcohol to get inside the pick-up.
SERVICING PRECAUTIONS
SECTION 1 GENERAL

1-3
NOTES REGARDING COMPACT DISC PLAYER REPAIRS
1. Preparations
1) Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). These components
are sensitive to, and easily affected by, static electricity. If such static electricity is high voltage, components
can be damaged, and for that reason components should be handled with care.
2) The pick-up is composed of many optical components and other high-precision components. Care must be
taken, therefore, to avoid repair or storage where the temperature of humidity is high, where strong
magnetism is present, or where there is excessive dust.
2. Notes for repair
1) Before 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 prevent AC leakage, the metal part of the soldering iron should be grounded.
5) Workers should be grounded by an armband (1MΩ)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent
static electricity changes in the clothing to escape from the armband.
7) The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.
CLEARING MALFUNCTION
You can reset your unit to initial status if malfunction occur(button malfunction, display, etc.).
Using a pointed good conductor(such as driver), simply short the RESET jump wire on the inside of
the volume knob for more than 3 seconds.
If you reset your unit, you must reenter all its settings(stations, clock, timer)
NOTE: 1. To operate the RESET jump wire, pull the volume rotary knob and release it.
2. If you wish to operate the RESET jump wire, it is necessary to unplug the power cord.

1-4
ESD PRECAUTIONS
Electrostatically Sensitive Devices (ESD)
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components
commonly are called electrostatically sensitive devices (ESD). Examples of typical ESD devices are
integrated circuits and some field-effect transistors and semiconductor chip components. The following
techniques should be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain
off any electrostatic charge on your body by touching a know earth ground. Alternatively, obtain and
wear a commercially available discharging wrist strap device, which should be removed for potential
shock reasons prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive
surface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.
4. Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static"
can generate electrical charges sufficient to damage ESD devices.
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 before removing the protective material from the leads of a replacement ESD device, touch
the protective material to the chassis or circuit assembly into which the device will by installed.
CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL
OTHER SAFETY PRECAUTIONS.
8. Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless
motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor
can generate static electricity sufficient to damage an ESD device).
[CAUTION. GRAPHIC SYMBOLS]
THE LIGHTNING FLASH WITH ARROWHEAD SYMBOL. WITHIN AN EQUILATERAL
TRIANGLE, IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE
OF UNINSULATED "DANGEROUS VOLTAGE" THAT MAY BE OF SUFFICIENT
MAGNITUDE TO CONSTITUTE A RISK OF ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENED TO
ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY
INFORMATION IN SERVICE LITERATURE.

1-5
LOCATION OF USERS CONTROLS
FRONT PANEL / REAR PANEL
WOOFER SYSTEM
AUX IN
SUB WOOFER
SPEAKER
RL
COMPONENT
Y MONITOR
OUT
S-VIDEO
OUT
VIDEO OUT
(PROGRESSIVE SCAN)
1. • DISC SKIP button
• OPEN / CLOSE button
• DISC SELECT buttons (DISC1, DISC2,DISC3)
2. NUMERIC buttons (0-9)
3. DISC DOOR
4. ( )POWER button
5. DISPLAY WINDOW
6. XDSS button
7. • (PROG./MEMO.) PROGRAM / MEMORY button
• ( REC/PAUSE )
RECORD / RECORD PAUSE button
• (PLAY MODE) PLAY MODE / DEMO button
• (SET/CD / (RDS-OPTIONAL) / AM-NOISE button
• FUNCTION SELECT buttons
(TUNER, KARAOKE/DVD, TAPE, USB, AUX / AV)
• VOLUME knob
• EQ button
• SURROUND button
• (MP3 OPT) MP3 OPTIMIZER button
• USER EQ button
MULTI JOG.
• MANUAL TUNING
• CD SKIP( SKIP )
• CLOCK ADJUST
• (b-KEY CON-#) KEY CONTROL
8. HEADPHONE Jack (PHONES): ø6.3mm
9. • GAME LINK connector (VIDEO IN, AUDIO L/R)
• USB connector ( )
10. PUSH EJECT position (TAPE 1)
PUSH EJECT position (TAPE 2)
11.• MIC VOLUME knob (MIC VOL.)
• MIC Jacks (MIC1 / MIC2) : ø6.3mm - OPTIONAL
12.OAO button
13.• AUTO TUNING DOWN/UP button
• REWIND / FAST FORWARD( )
• TEMPO DOWN(-) / TEMPO UP(+)
• PRESET DOWN / UP button
• STOP / CLEAR( ) button
• BACKWARD PLAY ( ) button - OPTIONAL
• FORWARD PLAY ( ) button
14.• CLOCK button
• TIMER button
• (ST. / MONO) STEREO/MONO,
(NOR.DUBB.) NORMAL DUBBING button
• CD SYNCHRO RECORDING (CD SYNC.),
HIGH DUBBING (HI-DUBB.) button
15.• COMPONENT VIDEO OUT
(PROGRESSIVESCAN) connector (Y Pb Pr)
• MONITOR OUT Jack
• S-VIDEO OUT Jack
16.SPEAKER Terminal
17.POWER CORD
18.SUBWOOFER SPEAKER Terminal
19.WOOFER SYSTEM Terminal
20.(AUX IN) AUXILIARY INPUT Jack
21.(FM/AM) ANTENNA Jack

1-6
1. POWER button
2. FUNCTION SELECT buttons
(TUNER / BAND, DVD / KARAOKE, AUX, USB)
3. NUMERIC buttons (0-9)
4. TAPE FUNCTION buttons
• REVERSE PLAY ( )
• PLAY ( )
• REWIND / FAST FORWARD PLAY ( )
• TAPE 1-2 SELECT buttons (1-TAPE-2)
• RECORD/ RECORD PAUSE ( /)
• TAPE STOP ( )
5. SET UP button
6. • ARROW buttons ( /)
(For use in highlighting a selection on a GUI
menu screen, TITLE and MENU screen.)
• PRESET (-/+) buttons ( )
• TUN. (-/+) buttons ( )
7. SELECT / ENTER button
8. MENU button
(Use the MENU button to display the menu screen
included on DVD video discs.)
9. STOP ( ), PAUSE( ) / STEP, PLAY ( ) buttons
10.PROG. / MEMO., REPEAT, REPEAT A-B buttons
11. EQ ,OAO, FEMALE( ), AUDIO / MALE( ),
SUBTITLE (S-TITLE), SHADOW, CLEAR buttons
12.ECHO VOL. ( ) buttons
13.MIC VOL. ( ) buttons
14.RDS, PTY buttons (OPTIONAL)
15.XDSS ,SURROUND(SURR.), ZOOM,
RETURN ( ) buttons
16.• MARKER, SEARCH, MUTE( ) buttons,
• SCAN ( ) / TEMPO (- / +), / KEY CON
(b/#)/, SKIP ( )
17.VOLUME -/+ buttons
18.TITLE button
(Use the TITLE button to display the title screen
included on DVD video discs.)
19.DISPLAY button
20.DIMMER button
21.SLEEP button
22.DISC SKIP (D.SKIP) button
REMOTE CONTROL

1-7
SPECIFICATIONS
• GENERAL
Power supply Refer to the main label.
Power consumption 200W
Net Weight 8.65kg
External dimensions (W x H x D) 280 X 365 X 370 mm
• TUNER/AMPLIFIER
FM Tuning Range 87.5 - 108.0MHz or 65 -74MHz, 87.5 -108.0MHz
Intermediate Frequency 10.7MHz
Signal to Noise Ratio 60 / 55dB (Mono / Stereo)
Frequency Response 140 - 10000Hz
AM Tuning Range 522 - 1620kHz or 520 - 1720kHz
Intermediate Frequency 450kHz
Signal to Noise Ratio 30dB
Frequency Response 140 - 1800Hz
Output Power Front : 270W + 270 W (6Ω, THD 10%)
Surround : 110W + 110 W (8Ω, THD 10%)
Subwoofer : 110W (6Ω, THD 10%)
T.H.D 0.7%
Frequency Response 42 - 20000Hz
Signal-to-noise ratio 75dB
• DVD / VCD / CD PLAYER • CASSETTE TAPE PLAYER
Frequency response (audio) 40 - 20000Hz Tape Speed 3000 3% (MTT-111.
Signal-to-noise ratio (audio) More than 75dB (1kHz) NORMAL-SPEED)
Signal-to-noise ratio (video) More than 55dB (1kHz) Wow Flutter 0.25%
Dynamic range (audio) More than 75dB (MTT -111, JIS-WTD)
Video output 1.0V (p-p), 75ΩF.F/REW. Time 120sec (C-60)
S-video output (Y) 1.0V (p-p), 75ΩFrequency Response 125 - 8000Hz
(C) 0.3V (p-p), 75ΩSignal to Noise Ratio 43dB
Component Video output (Y) 1.0V (p-p), 75ΩChannel Separation 50dB (P/B)/45dB (R/P)
(Pb) / (Pr) 0.7V (p-p), 75ΩErase Ratio 55dB (MTT-5511)
• SPEAKERS
Speaker Name Front Speaker (L/R) Subwoofer
Type Bass Reflex 3Way 3Speaker Bass Reflex 1Way 1Speaker
Impedance 6Ω6Ω
Frequency Response 55 - 20000Hz 43 - 1500Hz
Sound Pressure Level 86dB/W (1m) 84dB/W (1m)
Rated Input Power 270W 350W
Max. Input Power 540W 700W
Net Dimensions (W x H x D) 260 X 436 X 330mm 290 X 438 X 340mm
Net Weight 11.2kg 12kg
Speaker Name Surround Speaker (L/R)
Type Bass Reflex 2Way 2Speaker
Impedance 24Ω
Frequency Response 60 - 20000Hz
Sound Pressure Level 86dB/W (1m)
Rated Input Power 110W
Max. Input Power 220W
Net Dimensions (W x H x D) 210 X 436 X 285mm
Net Weight 4.5kg

1-8
MEMO

SMPS
SUB
MAIN
FRONT
DVD
SVC purchase order caution
MAIN board is array coming USB & JACK
board.
Purchase order board separately supply
incomprehensible.
Supply is possible in Location No A46 state
in exploded views.
450
303
452
A46U 454
266
450
450
453
265
450
292
450
261
293
274
268
270
271
A43
450
289
A00
291
450
277 281
451
282
455
A46J
276
453 296
450
278
301
283
456
450
283
450
453
A47
456
454
450
A46
450
274
269
CABLE5
A56
454
280
450
290
454
454
454
279
457
450
FAN
294
305
A52
285
CABLE1
260
259
265
450
288
255
250
450
450
CABLE6
248
A51 450
302
275 A41
A26
CABLE2 CABLE4
CABLE3
2-1 2-2
SECTION 2 EXPLODED VIEWS
CABINET AND MAIN FRAME SECTION