LG LX-230A User manual

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[CONTENTS]
❍ SECTION 1. GENERAL
• SERVICING PRECAUTIONS..................................................................................................... 1-2
• ESD PRECAUTIONS ................................................................................................................. 1-4
• SPECIFICATION ........................................................................................................................ 1-5
❍ SECTION 2. TROUBLESHOOTING
• ADJUSTMENTS ......................................................................................................................... 2-1
• TROUBLESHOOTING ............................................................................................................... 2-2
• WAVEFORMS OF MAJOR CHECK POINT............................................................................... 2-6
• BLOCK DIAGRAM.................................................................................................................... 2-15
• SCHEMATIC DIAGRAMS ........................................................................................................ 2-17
• WIREING DIAGRAM ................................................................................................................ 2-23
• PRINTED CIRCUIT DIAGRAMS .............................................................................................. 2-25
• INTERNAL BLOCK DIAGRAM OF ICs .................................................................................... 2-33
❍ SECTION 3. EXPLODED VIEWS
• CABINET AND MAIN FRAME SECTION................................................................................... 3-1
❍ SECTION 4. SPEAKER PART
• SPEAKER PART ........................................................................................................................ 4-1
❍ SECTION 5. REPLACEMENT PARTS LIST
• REPLACEMENT PARTS LIST .................................................................................................... 5-1

❏SERVICING PRECAUTIONS
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.
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Storage in conductive bag Drop impact
NEVER look directly at the laser beam, and don’t let
contact fingers or other exposed skin.
Magnet
How to hold the pick-up
Pressure
Pressure
Cotton swab
Conductive Sheet
SECTION 1. GENERAL

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.
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Armband
Conductive
Sheet
Resistor
(1 Mohm)
Resistor
(1 Mohm)
VOLUME KNOB
UP
DOWN
VOLUME
RESET jump wire

❐ 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 known 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]
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THE LIGHTNING FLASH WITH APROWHEAD 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 INTENDED TO
ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY
INFORMATION IN SERVICE LITERATURE.

❏ SPECIFICATIONS
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SECTION MODEL LX-230A
General Power supply Refer to the back panel of the unit
Power consumption 50W
Mass 4.35kg
Extemal dimensions(W X H X D) 161 X 255 X 268mm
CD Frequency Response 40 -18000Hz
Signal-to-noise ratio 70dB
Dynamic range 70dB
Tuning Range 87.5 -108.0MHz
Intermediate Frequency 10.7 MHz
FM Signal-to-noise ratio 60/55 dB
Frequency Response 60 -10000Hz
Tuning Range 522-1611kHz or 530-1610kHz
AM Intermediate Frequency 450kHz
Signal-to-noise ratio 35 dB
Frequency Response 100 -1800 Hz
AMP Output Power 18W
T.H.D 0.15%
Frequency Response 40-25000Hz
Signal-to-noise ratio 80dB
TAPE Tape Speed 4.75cm/sec
Wow Flutter 0.25% (MTT-111,JIS-WTD)
F.F/REW Time 120sec(C-60)
Frequency Response 250-8000Hz
Signal-to-noise ratio 43dB
Channel Separation 50dB(P/B)/45dB(R/P)
Erase Ratio 55dB (MTT-5511)
Speaker MODEL LXS-230
Type 1 Way 1 Speaker
Impedance 6Ω
Frequency Response 85-20000Hz
Sound Pressure Level 88dB/W(1m)
Rated Input Power 20W
Max.Input Power 40W
Net Dimension(W XH XD) 160 X 248 X 192mm
NOTE : Specification are subject to change without notice in the course of product improvement.
TUNER

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MEMO

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TAPE DECK ADJUSTMENT
1. AZIMUTH ADJUSTMENT
Figure 1. Azimuth Adjustment Connection Diagram
CH1 CH2
Speaker Out
Playback Mode
Head
Test Tape
MTT-114
L ch
R ch GND
Dual-trace
synchroscope
Electronic
Voltmeter
L out
R out
Unit
❏ ADJUSTMENTS
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.
Deck Mode Test Tape Test Point Adjustment Adjust for
Palyback MTT-114 Speaker Out DECK Screw Maximum
Azimuth Screw
SECTION 2. ELECTRICAL SECTION

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❏ TROUBLESHOOTING
• CD PART
Turn power on.
Is power on?
Does initial
read work?
Does it play?
Does it output
audio?
Check power supply circuit.
PN508 PIN8, 6.2V
PN508 PIN7, 5V
IC503 PIN2, 3.3V
Check the connector
PN503, PN504, PN507
Check the tracking servo.
Check the PN508 PIN1, 3
OK
NO
YES
YES
YES
NO
NO
NO
NO
NONO
Check the DISK circuit
Check the Laser
Check the focus circuit
Check the TRAKING servo.
NO
NO

- 2-3 -
A
B
2V
5V
0V
5V
0V
1V
2V
1.2V
0V
0.8V
FAILS TO INITIAL READ
NO NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
Disc motor turns
Does RF waveform
appear? IC501 Pin3
Check the Data transferred from PN507
pin8 to CD DSP
Check the Data transferred from
PN507 pin6 to MICOM
SLDO Voltage
(IC501 pin23)
Check the change of
SL +, SL - Voltage
(IC502 pin 18, 19)
Check the Voltage change of
PN 507 PIN2(OPEN, CLOSE)
Defective connector
PN507
Defective connector
PN507, Defective
MICOM
Defective
connector PN507,
Defective IC501
Defective IC501
Defective IC502
Defective contact PN503
Defective PICK-UP
Does laser light?
focus coil drive wareform.
TRACKING ERROR wareform
Is rotation normal?
Defective IC501
Defective PICK-UP
Is there no dropout of RF signal?
Does FA+ waveform appear at
IC502 pin18?
Does TE waveform appear at
IC501 pin15?

- 2-4 -
NO
NO
NO
NO
NO
NO
Laser does not light.
Is “3.5V” applied to pin80
of IC801?
Is power supplied to laser Q501?
(Q501 collector: about 1.8V)
Does laser current flow?
(R508’s voltage are 1.0V)
Is data transferred from
MICOM IC ?
Does voltage appear at IC
502 pin18, 19?
Defective MICOM.
Defective MICOM.
Defective connector.
Defective IC501, 502
Defective slide motor and/or
connector.
Defective LMT SW and/or
connector.
Defective Q 501 and/or laser.
Defective laser and/or
connector.
Did pickup return to
innermost circular?
Does it stop at inner pick
circular after shift?
Is defect output from LM
SW applied to pin 5 of
PN503?
R508 »1.0V
R508 «1.0V
YES
YES
YES
YES
OPEN CLOSE
YES
YES
YES
YES
YES
YES

- 2-5 -
B
NO
NO
NO
NO
NO
YES
YES
YES
YES
Laser lights
Does lens move up/down? Check the signal of FOCUS
SEARCH
(IC501 Pin 21)
Chekc the signal of PN502
pin 13, 14
Does FE signal appear?
(IC501 pin 13)
Does DRF signal appear?
(IC501 pin67)
Defective IC501
Defective IC502
Open activator and/or
connector
Defective IC501
Degraded laser diode
Defective PICK-UP

- 2-6 -
(CH1)
(CH2)
❏ WAVEFORMS OF MAJOR CHECK POINT
1. HF signal (RF signal ) waveform
(IC501 pin4) during normal play
2. EFM signal (IC501 pin 3)waveform
during Normal Play
3. Focus coil drive waveform(IC502 pin13)
• When focus search failed or there is no disc on the tray
• Focus coil drive waveform(FDO: IC501 pin21) and
DRF(IC501 pin67) when focus search is accomplished
4. Tracking coil drive waveform and TE during track
traverse
(1) When time division is 20mS/Div.1V/Div.
(3) When time division is 0.5nS/div.
(During backward Track Traverse)
5. Feed motor drive waveform(IC 502 pin18)
During normal play
CH1 : FOCUS COIL DRIVE
SIGNAL 2V/Div.
CH2 : DRF
CH1 : TRACKING COIL DRIVE
SIGNAL 2V/Div. (IC502 pin27)
CH2 : TRACKING ERROR(TE: IC501 pin15)
1V/Div.
(
(
(
CH1 : TRACKING COIL DRIVE (IC502 pin27)
SIGNAL 2V/Div.
CH2 : TRACKING ERROR (TE: IC501 pin15)
1V/Div.
(
CH1 : TRACKING COIL DRIVE (IC502 pin27)
CH2 : TRACKING ERROR (TE: IC501 pin15)
(
0.5V/Div.
500nS/Div.
(
1S/Div.
1V/Div.
(
1mS/Div.
1V/Div.
(
0.5V/Div.
5µS/Div.
(
2S/Div.
0.5V/Div.
OV
OV
OV
(CH1)
(CH2)
(CH1)
(CH2)
(CH2)
OV
OV
OV
OV
OV
OV
OV
OV
OV

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❏ AUDIO PART
VKK PART
Does DC - 27V appear at
PN601 pin .
Check the pattern of FRONT
PCB ASS’Y
Check the DC -34V of C928(-)
Check the DC -27V of
ZD 902(-)
Check the DC -27V of
Q901 “E”
Check the PATTERN
Replace the D936
Replace the ZD902
Replace the Q901
YES
YES
YES
YES
NO
NO
NO
NO
P-SENS PART
Does +5V appear at ZD901?
Check the pattern of
IC301 pin .
Check the waveform
of D937 (+).
Replace ZD901.
Replace the D937
YES
YES
NO
NO
26
16

- 2-8 -
POWER CIRCUIT
Check the Fuse
Check the DC output
of C923(+)
Check the DC 12V
Output of IC901
Check the DC 6.2V
output of IC902
Check the DC 12V
Output of IC903
Check the 5.6V of Q604 “C”
(CD FUNCTION)
END
Replace the Fuse
CHECK THE AC VOLTAGE
OF CN901 pin 5, 6
Check the DC VOLTAGE of
D939(+)
Replace the Q501
Replace the D925, D926,
D927, D928
Replace the IC902
Check DC VOLTAGE OF
D930(+)
Check the “LOW” of
IC501 pin8
Check the “High” of Q605“B”
Replace the Q604
Replace the IC902
Replace the Transformer
Replace the D939
Replace the D930
Replace the IC501
Check the “High” of
IC501 pin4
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO

- 2-9 -
AUDIO ABNORMAL
Check the signal output of
IC701 pin2, 4
Check the signal input of IC701
pin7, 11
Check the DC +9V of IC601
pin1
Check the “High” of Q702 “B”
Check the “High” of
IC701 pin5
Check the power of IC701
Check the connecting to
SPEAKER
YES
YES
YES
NO
NO
NO
MUTING CIRCUIT (MUTE)
Dose “High” appear at
Q701, Q751“B”
check the “Low” of Q701,
Q751, “C”
MUTE
Check the “High” of PN601 pin12
Check the “High” of
the IC301 pin2
Replace the Q703
Replace the TR
Refer to IC 301
Troubleshooting
YES
YES
YES
NO
NO
NO

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FUNCTION MODE AUDIO ABNORMAL
TAPE
Check the signal input
of IC601 pin6, 23
Refer to “IC201 Troubleshooting”
AUX
Chekc the signal input of IC601, pin 5, 24
Check the signal input of JK601
Check the signal input of IC601 pin 3, 26
Check the signal input of CN603 pin6, 8
Check the signal input of IC601 pin4, 25
Refer to “TUNER PACK Troubleshooting”
CD
TUNER

- 2-11 -
Refer to “IC301
Troubleshooting”
IC301 TROUBLESHOOTING
IC601 TROUBLESHOOTING
Check the power supplying IC301
pin 17, 46, 72, 90?
Refer to “Power Circuit Troubleshooting”
Check the P-SENS
Replace the X301
Check the RESET circuit
Refer to “Power Circuit Troubleshooting”
Check the Data of IC301 pin9, 10
(CD ➞ TAPE FUNCTION)
Replace the
IC601 Check the pattern
Check the P-SENS “High” of IC301 pin26
Check the oscillation of X301
When power supplying to IC301 pin12.
(Low ➞ High)
Replace the IC301
Check the power supplying
to IC601 pin1
Check the CLK Data of IC601 pin14, 15
Check the IC601 FUNCTION SELECTOR
END
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO

- 2-12 -
TUNER PACK TROUBLESHOOTING
Check the PLL- of CE, DI, DO, CLK
Is the normal ?
END
CE: Chip Enable
DI: Data Input(from u-com)
DO: Data Output(to u-com)
CLK: Tuner mode clock
Replace the TUNER PACK
YES
NO
TUNER PACK POWER TROUBLESHOOTING
Check the +9V of OPN602 pin2
Check the +DC C670
Check the pattern
Refer to “Power circuit
Troubleshooting”
Check the GND of PN602 pin4, 10
END
YES
YES
YES
NO
NO
PLAY
Check the VCC supplying to IC201 pin4
Refer to “Power Circuit
Troubleshooting”
Check the Deck Mecha
Replace the Deck
Mecha.
Replace the IC201
Check the signal output of IC201 pin3, 6
Check the “LOW” of Q201, Q251, “B”
YES
YES
YES
NO
NO
NO

- 2-13 -
REC (Q252, Q202 ON / R273, R223 HIGH)
Check signal supplied to IC203 pin2, 8 ?
Check the output of IC203 pin3, 7
Check the “voltage” of L201 pin5
Refer to “power circuit Troubleshooting”
Check the power
supplying to C227(+)
Check the oscillation
of Q204, “E”
Check the signal of
R212, R262
Check the Pattern
Check the Vcc power of IC203 Pin6
Check the oscillation of L201 pin 1, 3
Replace the DECK
Check the “Low” of Q202,
Q252 “B”
Replace the Q202, Q252
Check the “Low” of
IC501 pin9
Refer to
“Power Circuit
Troubleshooting”
Check the 0.6V of
Q205 “B”
Replace the L201
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO

- 2-14 -
MEMO