LG LF-U850D Bedienungsanleitung
MICRO HI-FI SYSTEM
SERVICE MANUAL
MODEL: LF-U850D, LF-U850A,
LFS-U850
SERVICE MANUAL MODEL: LF-U850D, LF-U850A, LFS-U850
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS” IN THIS MANUAL.
- 1-1 -
[CONTENTS]
❍SECTION 1.GENERAL
• SERVICING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
• ESD PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
• SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5
❍SECTION 2.ELECTRICAL SECTION
• TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
• INTERNAL BLOCK DIAGRAM of ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
• BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
• CD PART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
• WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26
• PRINTED CIRCUIT BOARD DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
❍SECTION 3. EXPLODED VIEWS
• CABINET AND MAIN FRAME SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
• Deck Mechanism Exploded View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
❍SECTION 4. SPEAKER PART
• MODEL:LFS-U850 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
❍SECTION 5. REPLACEMENT PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
- 1-2 -
SECTION 1. GENERAL
❏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.
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
Conductive Sheet
Cotton swab
Pressure
Pressure
- 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 magnet-
ism 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 (1M Ω)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent sta-
tic 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.
Resistor
(1 Mohm) Conductive
Sheet
Resistor
(1 Mohm)
Armband
RESET jump wire
VOLUME
VOLUME KNOB
DOWN
UP
- 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 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 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
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 gen-
erate 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 “DAN-
GEROUS 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.
- 1-5 -
❏SPECIFICATIONS
MODEL LF-U850D/A
SECTION
Power supply Refer to the back panel of the unit.
Power consumption 50 W
Mass 3.7 kg
Battery Operation 187 X 255 X 257 mm
Frequency response 40 - 18000 Hz
Signal-to-noise ratio 70 dB
Dynamic range 70 dB
Tuning Range 87.5 - 108.0 MHz or 65 - 74 MHz, 87.5 - 108.0 MHz
Intermediate Frequency 10.7 MHz
Signal to Noise Ratio 60/55 dB
Frequency Response 60 - 10000 Hz
Tuning Range 522 - 1620 kHz or 520 - 1720 kHz
Intermediate Frequency 450 kHz
Signal to Noise Ratio 34 dB
Frequency Response 120 - 2000 Hz
Output Power 80 W + 80 W
T.H.D 0.5 %
Frequency Response 42 - 20000 Hz
Signal-to-noise ratio 75 dB
Type Bass Reflex 3Way 4Speaker
Impedance 6 Ω
Frequency Response 60 - 20000 Hz
Sound Pressure Level 82 dB/W (1m)
Rated Input Power 80 W
Max. Input Power 160 W
Net Dimensions (WxHxD) 162x320x258 mm
Net Weight (1EA) 4.0 kg
[General][CD][Amp][Speakers]
[TUNER]
[AM] (MW)
[FM]
* Designs and specifications are subject to change without notice.
- 2-1 -
SECTION 2. ELECTRICAL SECTION
P-SENS PART CHECK
SMPS ASSY CN943 -> 4PIN 5V OPERATION CHECK
MAIN PCB PN101 4PIN 5V CHECK
MAIN PCB PN304 27PIN 5V CHECK
REFER TO SMPS TROUBLESHOOTING
❏ TROUBLESHOOTING GUIDE
YES
YES
NO
PN101 CONTACT STATUS CHECK
MAIN PCB PATTERN disconnection check
NO
FRONT CN304 7PIN 5V CHECK
YES
FRONT IC302 OPERATION AND INPUT VOLTAGE 4.7V~5.0V CHECK
YES
YES
U-COM 26PIN 5V CHECK
YES
IC302 INPUT VOLTAGE 4.7V OR ABOVE , OUTPUT VOLTAGE
3V OR ABOVE OPERATION CHECK
IC304 KIA7042 REPLACEMENT
NO
YES
VKK CHECK
CN943 6PIN DC -33V CHECK
MAIN PCB PN101 6PIN VOLTAGE -33V CHECK
REFER TO SMPS TROUBLESHOOTING
YES
YES
NO
MAIN PCB PATTERN DISCONNECTION CHECK
NO
PN304 3PIN VOLTAGE CHECK (-33V)
YES
FFC WIRE ASSEMBLY STATUS CHECK
NO
FRONT PCB CN304 3PIN VOLTAGE CHECK (-33V)
IC301 51PIN VOLTAGE CHECK
YES
FRONT PCB PATTERN DISCONNECTION CHECK
NO
- 2-2 -
U-COM 5V VOLTAGE CHECK
SMPS ASSY CN943 -> 3PIN 5V OPERATION CHECK
MAIN PCB PN101 3PIN 5VCHECK
REFER TO SMPS TROUBLESHOOTING
YES NO
MAIN PCB PN304 5PIN 5.6VCHECK
PN101 CONTACT STATUS CHECK
YES
MAIN PCB PATTERN DISCONNECTION CHECK
YES
NO
FRONT CN304 29PIN 5.6V CHECK
FFC WIRE ASSEMBLY STATUS CHECK
YES NO
U-COM 17,46,72,90PIN 4.7V~5V CHECK
FRONT PCB PATTERN DISCONNECTION CHECK
YES NO
Q303 (A103S) BASE "HIGH" CHECK
Q301, Q302,Q502,Q503(D1304S) BASE "HIGH" CHECK
C-COM 10PIN (HIGH) OPERATION STATUS CHECK
YES
IC603(CS5340) 10PIN,12PIN INPUT CHECK
IC603(CS5340) 2PIN (MCLK), 4PIN (SDOUT), 7PIN
(SCLK), 8PIN (LRCK) OUTPUT WAVEFORM CHECK
YES
Q303(A103S)OPERATION STATUS CHECK
YES
REPLACE Q303(A103S) IF FAULTY
YES
MUTE
YES
NO
REPLACE EACH APPROPRIATE TR
NO
C-COM 10PIN LINE CHECK AND U-COM
REPLACEMENT
NO
MUTING CIRCUIT TROUBLESHOOTING (ON MUTE CONDITION)
HEAD PHONE MUTE CHECK
- 2-3 -
FUNCTION INPUT UNFELT (IC601 BU4052)
CD FUNCTION
IC601 (BU4052)5,14PIN INPUT WAVEFORM CHECK
NORMAL OPERATION
U-COM (IC301)83PIN,84PIN COMMUNICATION CHECK.
MUTING MODE CHECK IC301 REPLACEMENT
C601 (BU4052)16PINVDD,8PIN VSS POWER CHECK
REPLACE APPROPRIATE PARTS
YES
YES
YES
YES
NORMAL
REPLACE APPROPRIATE PARTS
YES
YES
NORMAL
NORMAL
IC602 (MC4580) 4PIN VSS,8PIN VDD POWER CHECK. REFER TO SMPS
TROUBLESHOOTING
PN805 ASSEMBLY STATUS CHECK
YES
IC602 (MC4580) 2,6PIN INPUT WAVEFORM CHECK
YES
NO
NO
IC601 (BU4052)3,13PIN OUTPUT WAVEFORM CHECK
YES
NO
YES
FRONT CN304 MAIN PCB PN302 FFC WIRE
contact and assembly status check
NO
REPLACE FAULTY PARTS
- 2-4 -
AUX FUNCTION
IC601 (BU4052)4,11PIN INPUT WAVEFORM CHECK
NORMAL OPERATION
U-COM (IC301)83PIN,84PIN COMMUNICATION CHECK.
MAIN PCB PATTERN DISCONNECTION CHECK
IC601 (BU4052)16PINVDD,8PIN VSS POWER
CHECK
REPLACE APPROPRIATE PARTS
YES
YES
YES
YES
NORMAL
REPLACE APPROPRIATE PARTS
YES
YES
NORMAL
NORMAL
IC602 (MC4580) 4PIN VSS,8PIN VDD POWER
CHECK.
REFER TO SMPS
TROUBLESHOOTING
JK601 CONTACT STATUS CHECK
YES
IC602 (MC4580) 2,6PIN INPUT WAVEFORM CHECK
YES
NO
NO
IC601 (BU4052)3,13PIN OUTPUT WAVEFORM
CHECK
YES
NO
YES
FRONT CN304 MAIN PCB PN302 FFC
WIRE contact and assembly
NO
REPLACE FAULTY PARTS
Dieses Handbuch passt für folgende Modelle
2
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