LG DM2740 User manual

DVD Micro Hi-Fi System
SERVICE MANUAL
MODEL: DM2740 (DM2740, CMS2730F)
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
MODEL: DM2740 (DM2740, CMS2730F)SERVICE MANUAL
4102,JUNE76615056NFA:ON/P
Website http://biz.lgservice.com
Internal Use Only

CONTENTS
SECTION 1 ........ SUMMARY
SECTION 2 ........ CABINET & MAIN CHASSIS
SECTION 3 ........ ELECTRICAL
SECTION 4 ........ REPLACEMENT PARTS LIST
1-1

SECTION 1
SUMMARY
CONTENTS
SERVICING PRECAUTIONS................................................................................................................... 1-3
ESD PRECAUTIONS .................................................................................................................................. 1-5
FIRMWARE UPGRADE ............................................................................................................................. 1-6
1. MPEG
2. AUDIO MICOM
3. TOUCH
EEPROM OPTION SETTING................................................................................................................... 1-7
SYSTEM RESET .......................................................................................................................................... 1-7
SPECIFICATIONS ....................................................................................................................................... 1-8
1-2

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 lens.
6) Never attempt to disassemble the pick-up.
Spring has 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 allow
contact with fingers or other exposed skin.
Magnet
How to hold the pick-up
Conductive Sheet
Cotton swab
Pressure
Pressure
1-3
SERVICING PRECAUTIONS

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 or 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 (1 MΩ)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent stat-
ic 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.
Resistor
(1 MΩ)Conductive
Sheet
Resistor
(1 MΩ)
Armband
1-4

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.
1-5
ESD PRECAUTIONS

1-6
1. MPEG
1) Copy firmware to USB (Do not change file name).
Ex) LG_DM2740LD1_1403190.rom
2) Change function to DVD/CD by pressing input key, and wait until home menu is shown.
3) Inset USB device which includes firmware.
4) Firmware is detected automatically and then, shows blue screen in TV.
ÖIf home menu is maintained after inserting USB, press music Icon.
5) Take off the USB and press PLAY key.
6) and then, upgrading is started.
- Do not turn off the set until upgrade is finished.
7) After finishing firmware upgrading, set will restart automatically.
8) Power off and on again by pressing POWER key.
2. AUDIO MICOM
1) Copy firmware to USB (Do not change file name).
Ex) DM2740_1403250.HEX
2) Change function to DVD/CD by pressing input key, and wait until home menu is shown.
3) Inset USB device which includes firmware.
4) Firmware is detected automatically and then, shows blue screen in TV.
ÖIf home menu is maintained after inserting USB, press music Icon.
5) Upgrading is started.
- Do not turn off the set until upgrade is finished.
- Do not pull out the USB device using firmware upgrading.
6) After finishing firmware upgrading, set will be turned off.
3. TOUCH
1) Copy firmware to USB (Do not change file name).
Ex) DM2740T_1402040.dld / TC390_LG_CMDM2740_140204_0.hex
2) Change function to DVD/CD by pressing input key, and wait until home menu is shown.
3) Inset USB device which includes firmware.
4) Firmware is detected automatically and then, shows blue screen in TV.
=> If Home menu is maintained after inserting USB, press music Icon.
5) Upgrading is started.
- Do not turn off the set until upgrade is finished.
- Do not pull out the USB device using firmware upgrading.
6) After finishing firmware upgrading, set will be turned off.
FIRMWARE UPGRADE

1-7
1) Change function to DVD/CD by pressing input key, and wait until home menu is shown.
- Do not insert disc or USB at the set.
2) Press "PAUSE 1 4 7 2" in order.
3) and then, option setting menu is displayed.
You can see 10 bytes option value.
Ex ) F9 00 C1 D4 00 11 90 10 E0 08
4) Move a cursor by pressing Arrow < > key.
5) Press Num key what you want to change.
6) Press "PAUSE" key to exit option setting menu.
After change option value, you need to make system reset.
1) Change function to DVD/CD by pressing input key, and wait until home menu is shown.
- Do not insert disc or USB at the set.
2) Go to SETUP menu by pressing SETUP button in HOME menu.
3) Move highlight at "DISPLAY -> TV Aspect -> 16:9".
4) Press "1 3 9 7 1 3 9 Enter" in order.
5) and then, system reset menu is displayed.
6) Power off and on by pressing POWER key.
EEPROM OPTION SETTING
SYSTEM RESET

SPECIFICATIONS
• GENERAL
Power requirements Refer to the main label.
Power consumption Refer to the main label.
Dimensions (W x H x D) (135 x 295 x 315) mm
Net Weight (Approx.) 3.7 kg
Operating temperature 41 °F to 95 °F (5 °C to 35 °C)
Operating humidity 5 % to 90 %
• INPUTS/ OUTPUTS
VIDEO OUT 1.0 V (p-p), 75 Ω, sync negative, RCA jack x 1
HDMI OUT (video/audio): 19 pin Type A, HDMI™ Connector
DIGITAL IN (OPTICAL): 3 V (p-p), Optical jack x 1
PORT. IN 0.5 Vrms (3.5 mm stereo jack)
• SYSTEM
Laser Semiconductor laser, wavelength: 650 nm
Signal system Standard NTSC color TV system
Frequency response 20 Hz to 20 kHz (48 kHz, 96 kHz, 192 kHz sampling)
Signal-to-noise ratio More than 80 dB
Harmonic distortion 0.05 % at 1 W
Dynamic range More than 85 dB
Bus Power Supply 5 V 1 A
• AMPLIFIER
Stereo mode 80 W + 80 W (4Ωat 1kHz)
• TUNER
FM Tuning Range 87.5 to 108.0 MHz or 87.50 to 108.00 MHz
• FRONT SPEAKER
Type 3 Way 4 speaker
Impedance 4 Ω
Rated Input Power 80 W
Max. Input Power 160 W
Dimensions (W x H x D) (126 X 295 X 315) mm
Net Weight 3.5 kg
• Design and specifications ae subject to change without notice.
1-8

SECTION 2
CABINET & MAIN CHASSIS
CONTENTS
EXPLODED VIEWS..................................................................................................................................... 2-1
1. CABINET AND MAIN FRAME SECTION (DM2740) ................................................................................ 2-3
2. DECK MECHANISM SECTION (SDP-08) ................................................................................................ 2-5
3. PACKING ACCESSORY SECTION ......................................................................................................... 2-7
4. SPEAKER SECTION (CMS2730F)........................................................................................................... 2-8
2-1

2-2

B
F
445
A26
G
D
E
C
260L
260R
251 253
254
261
A47
264
263
A42 A43
A44
267
268
262
CABLE2
SMPS
FRONT
USB
A
470
462
462
462
265
462
462
462
252
273
B/T
C
EF
D
A
BA46
MAIN
464
H
H
269
A48
A52
CABLE4
291
NFC
462
462
464
G300
EXPLODED VIEWS
1. CABINET AND MAIN FRAME SECTION (DM2740)
NOTES) THE EXCLAMATION POINT WITHIN AN
EQUILATERAL TRIANGLE IS INTENDED
TO ALERT THE SERVICE PERSONNEL
TO THE PRESENCE OF IMPORTANT
SAFETY INFORMATION IN SERVICE
LITERATURE.

2. DECK MECHANISM SECTION (SDP-08)
011
010
037
023
012
012
012
A26
023C
023B

801 Owner’s Manual
808 Battery 825 FM antenna
823 HDMI cable
811 Video cable 900 Remote control
803 Packing
802 Box
804 Bag
3. PACKING ACCESSORY SECTION

A60L
A60R
4. SPEAKER SECTION (CMS2730F)

3-1
SECTION 3
ELECTRICAL
CONTENTS
ONE POINT REPAIR GUIDE ............................................................................................................................ 3-2
1. NO POWER PROBLEM ......................................................................................................................... 3-2
2. SPEAKER NO AUDIO OUTPUT ............................................................................................................ 3-3
3. USB NO DETECT................................................................................................................................... 3-4
4. NO BOOTING ......................................................................................................................................... 3-5
ELECTRICAL TROUBLESHOOTING GUIDE................................................................................................... 3-6
1. POWER (SMPS) ..................................................................................................................................... 3-6
2. P-SENS................................................................................................................................................... 3-6
3. VKK CHECK ........................................................................................................................................... 3-6
4. μ-COM PART CHECK-1 ......................................................................................................................... 3-7
5. μ-COM PART CHECK-2 ......................................................................................................................... 3-7
6. FLD DISPLAY CHECK ........................................................................................................................... 3-8
7. TOUCH PART CHECK ........................................................................................................................... 3-9
8. PWM MODULATION CHECK............................................................................................................... 3-10
9. POWER AMP PART CHECK ............................................................................................................... 3-11
10. VIDEO PART CHECK........................................................................................................................... 3-12
11. TUNER FUNCTION CHECK................................................................................................................. 3-13
DETAILS AND WAVEFORMS ON SYSTEM TEST AND DEBUGGING ....................................................... 3-14
1. SYSTEM 27 MHz CLOCK,RESET,FLASH R/W SIGNAL .................................................................... 3-14
2. SDRAM CLOCK.................................................................................................................................... 3-16
3. VIDEO PART (100% FULL COLOR-BAR) ........................................................................................... 3-16
4. HDMI PART .......................................................................................................................................... 3-17
WIRING DIAGRAM.......................................................................................................................................... 3-19
BLOCK DIAGRAM .......................................................................................................................................... 3-21
CIRCUIT DIAGRAMS ...................................................................................................................................... 3-23
1. SMPS CIRCUIT DIAGRAM .................................................................................................................. 3-23
2. MAIN - MICOM CIRCUIT DIAGRAM.................................................................................................... 3-25
3. MAIN - MPEG CIRCUIT DIAGRAM...................................................................................................... 3-27
4. MAIN - RF SERVO CIRCUIT DIAGRAM.............................................................................................. 3-29
5. MAIN - I/O & ADC CIRCUIT DIAGRAM ............................................................................................... 3-31
6. MAIN - PWM & AMP CIRCUIT DIAGRAM ........................................................................................... 3-33
7. FRONT VFD CIRCUIT DIAGRAM ........................................................................................................ 3-35
8. FRONT JACK CIRCUIT DIAGRAM ...................................................................................................... 3-37
CIRCUIT VOLTAGE CHART........................................................................................................................... 3-39
1. ICs......................................................................................................................................................... 3-39
2. CONNECTORS..................................................................................................................................... 3-41
3. CAPACITORS....................................................................................................................................... 3-41
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-43
1. SMPS P.C.BOARD ............................................................................................................................... 3-43
2. MAIN P.C.BOARD ................................................................................................................................ 3-47
3. FRONT VFD P.C.BOARD..................................................................................................................... 3-49
4. FRONT JACK P.C.BOARD................................................................................................................... 3-51

3-2
ONE POINT REPAIR GUIDE
1. NO POWER PROBLEM
No power problem occurs when you power on the unit.
1-1. Solution
Replace X100, IC101, IC103.
1-2. How to troubleshoot (Countermeasure)
1) Check X100 (Crystal).
 If it does not oscillate, change X100.
2) Check IC103 (Reset IC).
 IF its output voltage is not more than +2.7 V, change IC103.
3) Check IC101 (Micom).
 After Power is ON if the pin63 of IC101 is not ‘High’, change IC101.
But, the new μ-com IC need to write program.
1-3. Service hint (Any picture / Remark)
< MAIN board top view > < MAIN board bottom view >
IC101 X100
IC103

3-3
ONE POINT REPAIR GUIDE
2. SPEAKER NO AUDIO OUTPUT
No audio output problem occurs when you power on the unit.
2-1. Solution
Reassemble AMP IC heat-sink, replace IC700.
2-2. How to troubleshoot (Countermeasure)
1) Reassemble AMP IC heat-sink (heat-sink screw must be assembled tightly).
2) Still NG, please check IC700 Pin1, 2, 22(12 V), Pin29, 30, 31, 36, 37, 38 (26 V).
3) If it is not appear Vcc, change SMPS board assembly.
2-3. Service hint (Any picture / Remark)
< MAIN board top view >
IC700

3-4
ONE POINT REPAIR GUIDE
3. USB NO DETECT
When USB insert, USB no detect on the unit.
3-1. Solution
Replace IC311.
3-2. How to troubleshoot (Countermeasure)
1) Please check IC311.
Pin3 : 5 V
2) If it is not OK, replace IC3A8.
3-3. Service hint (Any picture / Remark)
< FRONT JACK board top view >
IC311

3-5
ONE POINT REPAIR GUIDE
4. NO BOOTING
When you turn on unit, it will display “Hello” or “Please wait” message continuously on front
panel, and it will not boot-up normally.
4-1. Solution
Replace X500.
4-2. How to troubleshoot (Countermeasure)
1) Please check the soldering status of 27 MHz crystal (X500).
2) Please check the frequency of 27 MHz crystal (X500).
3) If the crystal doesn’t oscillate, replace X500.
4) After changing it, if the set is still not booting, replace MAIN board assembly.
4-3. Service hint (Any picture / Remark)
< MAIN board top view >
X500