LG LX-U150X User manual

MODEL :LX-U150X(LXU-150)
SERVICE MANUAL
MICRO COMPONENT
SYSTEM
SERVICE MANUAL
MODEL : LX-U150X (LXS-U150)
http://biz.lgservice.com

- 1-1 -
SECTION 1. GENERAL
• SERVICING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
• ESD PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
• SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
SECTION 2. ELECTRICAL
• ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
• WAVEFORMS OF MAJOR CHECK POINT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
• TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
• BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
• WIRING DIAGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33
• PRINTED CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35
• INTERNAL BLOCK DIAGRAM OF ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-43
SECTION 3. EXPLODED VIEWS
• CABINET AND MAIN FRAME SECTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
SECTION 4. SPEAKER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
SECTION 5. REPLACEMENT PARTS LIST
• REPLACEMENT PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
[CONTENTS]

- 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 mag-
netism 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 -
Electrostatically Sensitive Devices (ESD)
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components com-
monly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated cir-
cuits 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 known earth ground.Alternatively, obtain and wear a com-
mercially 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 sur-
face 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 conduc-
tive 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 OBSERVEALL 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 gener-
ate static electricity sufficient to damage an ESD device).
CAUTION. GRAPHIC SYMBOLS
THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS
INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED “DANGER-
OUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE A RISK OF ELECTRIC
SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE SER-
VICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE LITERA-
TURE.
ESD PRECAUTIONS

- 1-5 -
SPECIFICATIONS
SECTION MODEL LX-U150A/D/X
Power supply Refer to the back panel of the unit
General Power consumption 20W
Mass 3kg
External dimensions(WxHxD) 146x238x251mm
Frequency Response 40 ~ 18000Hz
CD Signal-to-noise ratio 60dB
Dynamic Range 60dB
Tuning Range 87.5 ~ 108.0MHz or 65 ~74MHz, 87.5 ~ 108.0MHz
FM Intermediate Frequency 10.7MHz
Signal-to-noise ratio 55/50dB(Mono/Stereo)
Frequncy Response 60 ~ 1000Hz
Tuning Range 522 ~ 1620kHz or 520 ~ 1720kHz
AM Intermediate Frequency 450kHz
Signal-to-noise ratio 35dB
Frequency Response 100 ~ 1800Hz
Output Power 5W + 5W
AMP T.H.D 0.5%
Frequncy Response 60 ~ 20000Hz
Signal-to-noise ratio 60dB
Tape Speed 4.75cm/sec
Wow Flutter 0.3%(MTT-111, JIS-WTD)
F.F/REW time 120sec(C-60)
TAPE Frequency Response 250 ~ 8000 Hz
Signal-to-noise ratio 40dB(P/B)/38dB(R/P)
Channel Separation 32dB(P/B)/30dB(R/P)
Erase Ratio 50dB(MTT-5511)
MODEL LXS-U150
Type 1Way 1 Speaker
Impedance 4Ω
Frequency Response 100 ~ 18000Hz
SPEAKER Sound Pressure Level 86dB/W(1m)
Rated Input Power 5W
Max.Input Power 10W
Net Dimension(WxHxD) 146x238x185mm
Net weight 1.4kg
TUNER
NOTE : Specification are subject to change without notice in the course of product improvement.

- 1-6 -
MEMO

This set has been aligned at the factory and normally will not require further adjustment. As a result, it is
not recommended that any attempt is made to modificate any circuit. If any parts are replaced or if anyone
tampers with the adjustment, realignment may be necessary.
IMPORTANT
1. Check Power-source voltage.
2. Set the function switch to band being aligned.
3. Turn volume control to minimum unless otherwise noted.
4. Connect low side of signal source and output indicator to chassis ground unless otherwise specified.
5. Keep the signal input as low as possible to avoid AGC and AC action.
TAPE DECK ADJUSTMENT
TUNER ADJUSTMENT
Item Test Frequency Test Point Adjustment Adjust for Remark
DC Voltage FM 98MHz 60dBuV Oscilloscope L104 0V ± 50mV R145
AM IF AM 603kHz 80dBu Speaker out L103 Maximum Maximum Waveform
- 2-1 -
ADJUSTMENTS
SECTION 2. ELECTRICAL
Azimuth MTT-114 Speaker out Azimuth Maximum
Screw
Bias Frequency Tape Rec Tape Rec L201 65V ± 5kHz
Item Test Tape Test Point Adjustment Adjust for Remark
1
2
1
2

- 2-2 -
PIN9:FSEQ
PIN8:CE
PIN7:CL
PIN9:FSEQ
PIN8:CE
PIN7:CL
PIN6:DI
PIN6:DO
PIN4:RESET
PIN14:WRQ
PIN6:DI
PIN6:DO
PIN 4:RESET
PIN14:WRQ
#1. MICOM INTERFACE WAVEFORM
(PN805 PIN 3, 4, 5, 6) during power on
#1. MICOM INTERFACE WAVEFORM
(PN805 PIN 3, 4, 5, 6) during normal play
#1. MICOM INTERFACE WAVEFORM
(PN805 PIN 7, 8, 9) during power on
#1. MICOM INTERFACE WAVEFORM
(PN805 PIN 7, 8, 9) during normal play
WAVEFORMS OF MAJOR CHECK POINT

- 2-3 -
PIN 25 : FAO
PIN 16 : FA+
PIN 25 : FAO
PIN 16 : FA+
PIN 5 : SLIN
PIN 13 : SL+
PIN 5 : SLIN
PIN 13 : SL+
#2. SLED DRIVE AND MOTOR WAVEFORM
(IC802 PIN 5, 13) when focus search
#2. SLED DRIVE AND MOTOR WAVEFORM
(IC802 PIN 5, 13) during normal play
#3. FOCUS DRIVE AND MOTOR WAVEFORM
(IC802 PIN 25, IC802 PIN 16)
● When focus search failed or there is no disc on tray
#3. FOCUS DRIVE AND MOTOR WAVEFORM
(IC802 PIN 25, IC802 PIN 16)
● There is disc on tray and focus search success

- 2-4 -
PIN 2 : RFOUT
PIN 10 : FE
PIN 16 : TE
PIN 22 : TAO
PIN 17 : TA+
PIN 6 : SPIN
PIN 11 : SP+
#5. TRACK DRIVE AND MOTOR WAVEFORM
(IC802 PIN 22 , IC802 PIN 17) during normal play
#4. SPINDLE DRIVE AND MOTOR WAVEFORM
(IC802 PIN 6, 11) when TOC reading
#6. RF, FOCUS AND TRACKING ERROR WAVEFORM
(IC801 PIN 2, 10, 16) during normal play

- 2-5 -
• AUDIO PART
TROUBLESHOOTING
P-SENS PART
Does +5V appear at ZD902?
YES NO
POWER CIRCUIT
Check the DC output
Of C914(+)
Check the DC 9V
Output of IC903
END
NO
YES
NO
NO
YES
YES
NO
YES NO
YES
NO
YES
NO
YES NO
YES
IC300 PIN 26 Check
Check the Fuse
Check the DC 6.02V
Output of IC902
Check the 5V of Q9011 "C"
(CD FUNCTION)
Replace the fuse
Check the DC voltage of
CN901 Pin3,4 Replace the
Transformer
Replace the
Transformer
Replace the D908,909
910,911
Check the DC voltage of
CN901 Pin 8 , Pin 9
Replace the D908,909,
910,911
Replace the D902,903
Check the "High" of
Q902 "B"
Replace the Q901
Check the "High"
Of CN601 pin7
D920 , CN901 Check

- 2-6 -
MUTING CIRCUIT(MUTE)
YES
NO
NO
NO
AUDIO ABNORMAL
YES
NO
YES
NO
YES
NO
YES
NO
YES
Check the "LOW" of Q701
Q901, "C"
Check the Output of IC701
Pin 8,12
Check the waveform
Of D920(+)
Replace ZD902
Check the Signal
Output of IC701 pin2,4
Check the DC 10V
of IC601 Pin1
Check the DC 9V
of IC903
Check the Power Circuit
Check the speaker
connection
Check the "High" of
IC701 pin5
Check the FUNC input
Normal
Does "High" appear at
Q701, Q702 "B"
MUTE
Replace the TR

- 2-7 -
FUNCTION MODE AUDIO ABNORMAL
NO
YES NO
NO
YES
NO
YES
NO
YES
Check the signal input of
IC601 pin3, 26
TAPE
Check the signal input of
IC601 pin4, 25
Check the signal input of
IC601 pin6, 23
Check the signal input of
IC601 pin5, 24
IC601 pin12, 17 output
IC601 pin12, 17 output
IC601 pin12, 17 output
CN201, PN201 check
IC201 pin4, 11 check
Check signal input JK602
Check the signal input of CN601 pin
1, 3 and refer to CD troubleshooting
IC102 pin17, 18 check
CD
TUNER
AUX
IC601 pin12, 17 output

- 2-8 -
IC301 TROUBLESHOOTING
NO
YES
IC601 TROUBLESHOOTING
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
Check the power supplying IC300 pin17,54,90
Check the P-SENS "HIGH" of IC300 pin26
Check the oscillation of X301
When power supplying to IC300 pin11.
(Low High)
Refer to "Power Circuit Troubleshooting"
Check the P-SENS
Replace the X301
Check the RESET circuit
Check the power supplying
To IC601 pin1
Check the CLK Data of IC601 pin14, 15
Check the Control function
END
Refer to "Power Circuit Troubleshooting"
Check the Data of IC300 pin6, 7
(CD TAPE FUNCTION)
Replace the
IC201 Check the pattern
of IC300, IC601
Refer to IC300
Troubleshooting
Replace the IC300

- 2-9 -
IC103 TROUBLESHOOTING
NO
YES
NO
YES
NO
YES
AM COIL TROUBLESHOOTING
YES
NO
YES
NO
YES
Check the Power input of IC103 Pin 17
X104 oscillation
Check CE,DI,DO,CLK
Check the Operation
END
Check the "High" L102 Pin 2
Replace X104
D107 ,D108 ,IC902 Check
CE : Chip Enable
DI : Data input (from Micom)
DO : Data output (to Micom)
CLK : Tuner mode clock
Check the oscillation the L102 Pin 13
Refer to "IC103 Troubleshooting"
Check the IC102 Troubleshooting
Replace to L102

- 2-10 -
FM(TU101) TROUBLESHOOTING
YES
IC 102 TROUBLESHOOTING
NO
NO
YES
YES
NO
NO
YES NO
YES NO
YES
YES
YES
NO
YES
YES NO
Check the 10V input of TU101 Pin 6
Check the "High" of TU101 Pin5
Check the Power input of IC102 pin8
Check the 10V of Q102 "E"
Check the OSC waveform of
TU101 pin8
Refer to "IC102 Troubleshooting"
Check the waveform of IC102 pin16, 17
Check the "LOW" of IC103
pin7
Replace the Q102
Refer the TU101
Check the Power circuit
Refer to "IC103
Troubleshooting"
Check the waveform of IC102 pin20, 21
IC903,D105,D106 Check
Check the
FM(TU101) ,AM(L102)
Replace the IC102
Replace the IC103
Check the "LOW" of
IC102 pin13 Refer to "IC103
Troubleshooting"
END

- 2-11 -
DECK PLAY
NO
YES
NO
YES
RECORDING
YES NO
YES
NO
YES
Check the B+ Power to Leaf Switch
IC201 signal check Pin 4 , Pin 11
Check the signal output
IC201 Pin 4 , Pin 11
PN202 Check
SW202 Check
Check PN201 , Q201
Audio output ( PN201 Pin 8 , Pin 9 )
Check the oscillation of L201
Check the signal input to
PN201 Pin 8 , Pin 9
Check Leaf S/W B+
Check R218,L201,L204
Check Head Connector ( PN202 )
Check the PN201
Pin 4 , Pin 5

- 2-12 -
• CD PART
NO
YES
NO
YES
NO
YES
NO
YES
TURN ON CD
OPEN CLOSE CHECK
"READING"
DISPLAY CHECK
READING OK CHECK
IF PLAY, AUDIO
OUTPUT CHECK
CONNECTOR CHECK ( CN808 ,PN305 )
PN304 PIN 12 (LEAF S/W) VOLTAGE CHECK
-. OPEN : 5V , CLOSE : 2.5V
CHECK POWER SUPPLY CIRCUIT( PN601 )
CONNECTOR CHECK ( CN802 ,PN601)
CHECK MICOM INTERFACE CIRCUIT( PN305 )
CHECK MICOM INTERFACE CIRCUIT( PN305 )
CONNECTOR CHECK( PN801,CN802 )
CHECK PICKUP MOVEMENT
CHECK LC78690W (IC801)
CHECK SA5810 (IC802)
CONNECTOR CHECK (PN601)
OK

- 2-13 -
OPEN CLOSE NG
NO
YES
NO
YES
NO
CONNECTOR LOCKING CHECK ( CN808 )
CHECK POWER SUPPLY CIRCUIT( PN305,PN601)
PN305 PIN 12 = 5V
PN601 PIN 7 =5V
PN305 PIN 13 (LEAF S/W) VOLTAGE CHECK
OPEN : 5V , CLOSE : 2.5V
IC902(KIA7805)
CHECK
DEFECTIVE MICOM
IC300 PIN 20 (LEAF S/W) VOLTAGE CHECK
DEFECTIVE IC300