LG FFH-1850, FFH-2850-AX Service 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

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.

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Armband

Conductive Sheet

Resistor (1 Mohm)

VOLUME KNOB

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.

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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

..........................................................................................................................................

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)

...........................................................................................................................

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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.

YES

- 2-4 -

Fails to initial read

1.3V

YES

NO NO NONO

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.

- 2-5 -

A

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 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

OPEN

YES

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