LG FFH-185A 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 ............................................................................................... 2-8
• BLOCK DIAGRAM ...................................................................................................................................... 2-9
• SCHEMATIC DIAGRAMS......................................................................................................................... 2-11
• WIRING DIAGRAM .....................................................................................................................................2-19
• PRINTED CIRCUIT DIAGRAMS............................................................................................................... 2-21
• INTERNAL BLOCK DIAGRAM OF ICs ..................................................................................................... 2-30
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

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.
- 1-2 -
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

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.
- 1-3 -
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
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.
- 1-4 -

SPECIFICATIONS
1. AMP SECTION
1) Power Output (6 Ω, 2 channel, T.H.D. 10%) .......................................................................... 20W+20W
2) T.H.D............................................................................................................................................ 0.15%
3) Frequency Response (-3dB down).................................................................................... 42Hz~25kHz
4) Signal-to-noise Ratio...................................................................................................................... 80dB
5) Input Sensitivity AUX ............................................................................................................ 400±50mV
6) Channel Difference 1kHz ................................................................................................................. 2dB
2. TUNER SECTION
1) FM
1) Frequency Range..................................................................................................... 87.5MHz~108MHz
2) Intermediate Frequency ........................................................................................................... 10.7MHz
3) Sensitivity (90/98/106MHz) ............................................................................................................ 12dB
4) Signal-to-noise Ratio 98.1MHz(Mono/Stereo)...................................................................... 64dB/55dB
5) Image Rejection 106.1MHz............................................................................................................ 18dB
6) IF Rejection 90.1MHz .................................................................................................................... 60dB
7) Distortion 98.1MHz(Mono/Stereo)............................................................................................ 1.2/1.2%
8) Frequency Response (-3dB) ............................................................................................. 60Hz~10kHz
9) Stereo Separation (100Hz/1kHz/10kHz)........................................................................................ 25dB
2) AM(MW)
1) Frequency Range ...................................................................................................... 522kHz~1611kHz
2) Intermediate Frequency ............................................................................................................. 455kHz
3) Usable Sensitivity....................................................................................................................... 55dB/m
4) Image Rejection (1404kHz) ........................................................................................................... 20dB
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~1800Hz
3) SW(OPTIONAL)
1) Frequency Range......................................................................................................... 5.8MHz~18MHz
2) Intermediate Frequency ............................................................................................................. 450kHz
3) Usable Sensitivity....................................................................................................................... 40dB/m
4) Signal To Noise Ratio .................................................................................................................... 35dB
5) Distortion .......................................................................................................................................... 3%
4) 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%
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3. TAPE DECK SECTION
1) Tape Speed (MTT-111) / Normal Speed................................................................................. 4.75cm/sec
2) Wow Flutter (MTT-111) ................................................................................................................. 0.25%
3) Fast Forward and Rewind Time (C-60)......................................................................................... 120sec
4) Frequency Response (6dB range)....................................................................................... 250Hz~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/45dB
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/47dB/40dB
6) Access Time (Short / Long)...................................................................................................... 2sec/6sec
5. GENERAL
1) Power requirement ................................................................................... Refer to the back panel of unit
2) Power consumption........................................................................................................................... 60W
3) Dimension (W x H x D) ....................................................................................... 180 x 248 x 241.3 (mm)
NOTE : Specification are subject to change without notice in the course of product improvement.
- 1-6 -

- 2-1 -
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
Palyback MTT-114 Speaker Out DECK Screw Maximum
Azimuth Screw
2. 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 L201 60kHz±5kHz (Auto stop)
WIRE(PN201) 85kHz±5kHz(Auto Reverse)
Figure 2. Record Bias Adjustment Connection Diagram

- 2-2 -
3. TUNER ADJUSTMENT
Figure 3. Tuner(S curve) Adjustment Connection Diagram
Unit
Signal Generator
GND
Electronic
OSCILLOSCOPE
FM Antenna
Terminal Speaker
Item Test Point Adjustment Adjust for
DC Voltage Check Point TP1, TP2 L101 0V±50mV
(FM)

- 2-3 -
TROUBLESHOOTING
Turn power on.
Is power on?
Does initial read work?
Does it play?
Does it output audio?
Check power supply circuit.
(Check PN 501)
Check laser circuit.
Check focus circuit.
Check disc.
Check tracking servo circuit.
Check audio circuit.
OK
YES
YES
YES
YES
NO
NO
NO
NO

- 2-4 -
Fails to initial read
1.3V
A
B
YES YES
YES
YES
YES
YES
YES
YES
NO
NO
NO NO NONO
NO
NO
NO
NO
Does laser light?
Disc motor turns.
Does RF
waveform
appear?
Test Pin(RF)
Does tracking
servo work?
Lower envelope
of Test Pin(RF)
waveform is flat.
Does signal
appear at Test
Pin(TEO)?
Does signal appear at IC 502
Pin and Pin ?
Does GFS (IC503 pin 25)
show as below?
Is rotation normal?
Is there no dropout of RF
signal?
Does TE2 signal
appear at pin
of IC501? Defective IC
801, pick up
and/or open
wire.
Detective pattern.
Defective IC 501
and/or IC 502
Defective pick-up
and/or connector.
Defective IC 503.
Scratch in disc
initial read area.
Defective pick-up
adjustment focus offset.
53
26 27

- 2-5 -
A
NO
NO
NO
NO
NO
NO
Laser does not light.
Is “3.5V” applied to pin of IC 501?
Is power supplied to laser Q501?
(Q 501 collector: about 1.8V)
Does laser current flow?
1.0V across R507
Is data transferred from
MICOM IC ?
Does voltage appear at IC
502 pin , ?
Defective MICOM.
Defective MICOM.
Defective connector.
Defective IC 501, 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 of
PN503?
R507»1.0V
R507«1.0V
YES
YES
YES
YES
OPEN CLOSE
YES
YES
YES
YES
YES
YES
70
17 18
5

- 2-6 -
B
C
Does lens move up/down?
Does IC 501 out focus
search signal?
IC 501 pin (FEO)
Is focus search signal
applied to pin , of
PN502?
Laser lights.
Confirm
initial
read with
disc
Defective IC501
Defective IC502
Defective IC 501.
Open activator and/or
connector.
Open connector and/or
defective IC 501.
Incorrect turntable height.
Degraded laser diode.
Does Test Pin RF signal appear even in
low level?
Is laser output adjustment correct?
Does FOK(focus ok) signal appear?
YES
YES
YES
YES
YES
YES
IC501 Pin (RF)
IC501 pin
(FOK)
NO NO
NO
NO
NO
NO
48
13 16
40
74

- 2-7 -
FER
ISTAT(SENSE)
C
Start mode
Does FE1 signal appear? IC 501 pin
Does FZC signal (focus zero cross signal)
appear at pin of IC 501, ISTAT (SENSE)
terminal?
Does SMON signal appear
at pin of IC 503?
Does SMPO signal appear
at pin of IC 503?
Is drive voltage applied to disk motor?
Defective IC 501.
Open pick diode
Defective IC 501.
Defective Pattern between IC 501 and
IC 502.
Defective IC 501, 502 and/or
peripheral circuit.
Defective disk motor and/or insulation.
(Focus servo turns
ON by FZC signal
of FOK mod.)
NO
NO
NO
NO
YES
YES
YES
YES
YES
73
75
31
59

- 2-8 -
(CH1)
(CH2)
WAVEFORMS OF MAJOR CHECK POINT
1. HF signal (RF signal ) waveform
(Test Point) during normal play
2. EFM signal (pin IC 501)waveform
during Normal Play
3. Focus coil drive waveform(Pin NO 1, 2 of IC 502)
• When focus search failed or there is no disc on the tray
• Focus coil drive waveform(pin NO 1, 2 of IC 502) and
FOK (pin NO of IC 501) when focus search is
accomplished
4. Tracking coil drive waveform (pin NO , of IC 502)
and TEO during track traverse
(1) When time division is 20nS/div
(2) When time division 0.5nS/div.
(During forward track traverse)
(3) When time division is 0.5nS/div.
(During backward Track Traverse)
5. Feed motor drive waveform(pin NO 11, 12 of IC 502)
During normal play
CH1 : FOCUS COIL DRIVE
SIGNAL 2V/Div.
CH2 : FOAK
CH1 : TEO(Test Point)
1V/Div.
CH2 : TRACKING COIL DRIVE
SIGNAL 2V/Div.
(
(
(
CH1 : TEO(Test Point)
1V/Div.
CH2 : TRACKING COIL DRIVE
SIGNAL 2V/Div.
(
CH1 : TEO(Test Point)
1V/Div.
CH2 : TRACK COIL DRIVE
SIGNAL 2V/Div.
(
40
26
33
27
0.5V/Div.
500nS/Div.
(
2V/Div.
500nS/Div.
(
0.5V/Div.
500nS/Div.
OV
OV
OV
(CH1)
(CH2)
(CH1)
(CH2)
(CH2)
OV
OV
OV
OV
OV
OV
OV
OV
OV

2-9 2-10
BLOCK DIAGRAM
NOTE:
1. Shaded(■) parts are critical for safety.Replace only
with specified part number.
2. Voltages are DC-measured with a digital voltmefer
during Play mode.
NOTE: Warning
Parts that are shaded are critical With respect
to risk of fire or electrical shock.

SCHEMATIC DIAGRAMS
• MAIN SCHEMATIC DIAGRAM
2-11 2-12
NOTE:
1. Shaded(■) parts are critical for safety.Replace only
with specified part number.
2. Voltages are DC-measured with a digital voltmefer
during Play mode.
NOTE: Warning
Parts that are shaded are critical With respect
to risk of fire or electrical shock.

2-13 2-14
• FRONT/POWER SCHEMATIC DIAGRAM

• TUNER SCHEMATIC DIAGRAM
2-15 2-16

• CDP SCHEMATIC DIAGRAM
2-17 2-18

WIRING DIAGRAM
2-19 2-20
NOTE: Warning
Parts that are shaded are critical With respect
to risk of fire or electrical shock.