LG FFH-3765MVA User manual

- 1-1 -
CONTENTS
SECTION 1. GENERAL
• SERVICING PRECAUTIONS ..................................................................................................................... 1-2
• ESD PRECAUTIONS.................................................................................................................................. 1-4
• SPECIFICATIONS ...................................................................................................................................... 1-5
SECTION 2. ELECTRICAL
• ADJUSTMENTS.......................................................................................................................................... 2-1
• TROUBLESHOOTING ................................................................................................................................ 2-3
• WAVEFORMS OF MAJOR CHECK POINT ............................................................................................. 2-20
• BLOCK DIAGRAM .................................................................................................................................... 2-21
• SCHEMATIC DIAGRAMS......................................................................................................................... 2-23
• PRINTED CIRCUIT DIARGAMS............................................................................................................... 2-33
• INTERNAL BLOCK DIAGRAM OF IC’s .................................................................................................... 2-43
• REPAIRS REGARDING CD MECHANISM .............................................................................................. 2-55
SECTION 3. EXPLODED VIEWS
• CABINET AND MAIN FRAME SECTION ................................................................................................... 3-1
• TAPE DECK MECHANISM: AUTO STOP DECK(OPTIONAL) ................................................................... 3-3
• TAPE DECK MECHANISM: AUTO REVERSE DECK................................................................................. 3-5
• CD MECHANISM ......................................................................................................................................... 3-7
SECTION 4. SPEAKER.............................................................................................................................. 4-1
SECTION 5. REPLACEMENT PARTS LIST........................................................................................... 5-1

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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
Pressure
Pressure
Cotton swab
Conductive Sheet

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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 TACT SWITCH 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 TACT SWITCH, pull the volume rotary knob and release it.
2. If you wish to operate the RESET TACT SWITCH, it is necessary to unplug the power cord.
Armband
Conductive
Sheet
Resistor
(1 Mohm)
Resistor
(1 Mohm)
VOLUME KNOB
UP
DOWN
VOLUME
RESET TACT SWITCH

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
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.
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SPECIFICATIONS
1. AMP SECTION
1) Power Output (6 Ω, 2 channel, T.H.D. 10%) .......................................................................... 50W+50W
2) T.H.D.............................................................................................................................................. 0.2%
3) Frequency Response (-3dB down).................................................................................... 42Hz~25kHz
4) Signal-to-noise Ratio...................................................................................................................... 80dB
5) Input Sensitivity AUX ............................................................................................................ 400±50mV
6) Channel Difference 1kHz ................................................................................................................. 3dB
2. TUNER SECTION
1) FM/OIRT
1) Frequency Range..................................................................................................... 87.5MHz~108MHz
................................................................................................or 65.0MHz~74.0MHz & 87.5MHz~108MHz
2) Intermediate Frequency ........................................................................................................... 10.7MHz
3) Sensitivity (70MHz/78.6MHz/83.0MHz/86.6MHz/90MHz/98MHz) ................................................. 12dB
4) Signal-to-noise Ratio 98.1MHz(Mono/Stereo)...................................................................... 61dB/58dB
5) Image Rejection 106.1MHz............................................................................................................ 20dB
6) IF Rejection 90.1MHz .................................................................................................................... 65dB
7) Distortion 98.1MHz(Mono/Stereo)............................................................................................ 1.2/1.5%
8) Frequency Response (-3dB) ............................................................................................. 60Hz~10kHz
9) Stereo Separation (100Hz/1kHz/10kHz)........................................................................................ 25dB
2) AM(MW)
1) Frequency Range......................................................................... 522kHz~1611kHz/530kHz~1720kHz
2) Intermediate Frequency ............................................................................................................. 450kHz
3) Usable Sensitivity........................................................................................................................... 55dB
4) Image Rejection (1404kHz) ........................................................................................................... 23dB
5) IF Rejection (603kHz) .................................................................................................................... 40dB
6) Selectivity (1008kHz) ................................................................................................................... ±23dB
7) Signal-to-noise Ratio (1008kHz) .................................................................................................... 35dB
8) Distortion (1008kHz) ...................................................................................................................... 1.5%
9) Frequency Response (1008kHz)................................................................................... 100Hz~2000Hz
3) LW(OPTIONAL)
1) Frequency Range ........................................................................................................ 153kHz~281kHz
2) Intermediate Frequency ............................................................................................................. 450kHz
3) Usable Sensitivity........................................................................................................................... 65dB
4) Signal To Noise Ratio (200kHz)..................................................................................................... 28dB
5) Distortion (200kHz) ........................................................................................................................... 3%

3. TAPE DECK SECTION
1) Tape Speed (MTT-111) / Normal Speed ............................................................................. 3(±1.5%)kHz
2) Wow Flutter (MTT-111) ................................................................................................................. 0.25%
3) Fast Forward and Rewind Time (C-60) ........................................................................................ 120sec
4) Frequency Response (6dB range) ...................................................................................... 125Hz~8kHz
5) Signal-to-noise Ratio (Playback/Record)................................................................................ 43dB/43dB
6) Distortion (Playback/Record) ...................................................................................................... 3% / 4%
7) Crosstalk (Playback: 1kHz).............................................................................................................. 55dB
8) Channel Separation (Playback: 1kHz) ............................................................................................. 50dB
9) Erase Ratio ...................................................................................................................................... 55dB
4. COMPACT DISC PLAYER SECTION
1) Frequency Response (40Hz-18kHz) ..................................................................................... +0.5/-3.0dB
2) Signal-to-noise Ratio (1kHz) ............................................................................................................ 70dB
3) Dynamic Range (1kHz).................................................................................................................... 70dB
4) T.H.D. (1kHz) ................................................................................................................................... 0.2%
5) Separation (100Hz/1kHz/10kHz)................................................................................... 45dB/45dB/40dB
6) Access Time Short / Long / LEAD IN .............................................................................. 3sec/6sec/9sec
5. GENERAL
1) Power requirement ................................................................................... Refer to the back panel of unit
2) Power consumption ......................................................................................................................... 100W
3) Dimension (W x H x D).......................................................................................... 273 x 326 x 360 (mm)
4) Weight (net) ..................................................................................................................................... 7.3kg
NOTE : Specification are subject to change without notice in the course of product improvement.
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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
SECTION 2. ELECTRICAL
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
A Deck Playback MTT-114 Speaker Out DECK Screw Maximum
Azimuth Screw
B Deck Playback MTT-114 Speaker Out Azimuth Screw Maximum
2. MOTOR SPEED ADJUSTMENT
Figure 2. Motor Speed Adjustment Connection Diagram
Head Playback Mode
Unit
Speaker Out
GND
L out
R out
Record/Playback
head
Test Tape
MTT-111
Frequency Counter
Deck Mode Test Tape Test Point Adjustment Adjust for Remark
Normal Speed MTT-111 Speaker Out VR201 3kHz ± 1% A Deck
HI-Speed MTT-111 Speaker Out more than 5.4kHz HI-Speed Dubbing Mode

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3. RECORD BIAS ADJUSTMENT
Head
Unit
PN202
GND
Record/Playback
head
Test Tape
MTT-5511
Record/Playback
and Pause Mode Frequency Counter
Deck Mode Test Tape Test Point Adjustment Adjust for
Rec/Pause MTT-5511 ERASE HEAD L203 60kHz±5kHz (Auto stop)
WIRE(PN202) 85kHz±5kHz(Auto Reverse)
Figure 3. Record Bias Adjustment Connection Diagram
4. TUNER ADJUSTMENT
Figure 4. Tuner(S curve) Adjustment Connection Diagram
Unit
Signal Generator
GND
Electronic
OSCILLOSCOPE
FM Antenna
Terminal Speaker
Item Test Point Adjustment Adjust for
DC Voltage Checker PIN TP101, 102 L106 0V±50mV
Item Test Point Adjustment Adjust for
AM IF SPEAKER OUT L110 OUTPUT MAXZMUM
(FM)
(AM)

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TROUBLESHOOTING
■ CD SECTION
CD PART
CD Function Select
Does initial reading occur?
Can disc be palyed?
OK
Check power supply circuitry.
Check laser circuitry.
Check focusing circuit.
Check disc.
Check tracking servo circuitry.
Check Audio circuitry.
Is power turned ON?
Is audio output supplied?
YES
YES
YES
NO
NO
NO
NO
YES

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A
B
Does disc motor rotate?
Does laser light?
Is RF waveform
output?
RFO
IC501 Pin
Is tracking servo
operating?
Is the lower enve-
lope of RFO
waveform flat?
1.3V
Is signal output at
(TEO)?
Is signal output, at
IC501 Pin ?
16
(FEO)
• Pattern defective.
• IC501 or IC502 defective.
Does IC502 Pin (GFS) as
figure?
Is rotation normal?
Is there any irregularity in
frequency?
Is HF signal normal without
dropout?
• Pick-up defective.
• Connector defective.
Is signal output at tracking output
IC503 Pin , ?
• IC502 defective.
• Disc initial reading damaged or
defective.
• Disc defective.
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO NO NO
If initial reading is not carried out (with disc)
35
15
36
57
• IC501 defective.
• Connector
defective.
• Pick-up
defective.
PN801 Pin , waveform.
14 15