LG HT904TA User manual

MODEL:HT904TA(HT904TA, SH94TA-F/S/C/W)SERVICE MANUAL
MODEL: HT904TA
Website http://biz.lgservice.com
Internal Use Only
DVD RECEIVER SySTEM
SERVICE MANUAL
(HT904TA, SH94TA-F/S/C/W)
P/NO : AFN73078818 JUNE, 2009

1-1
[CONTENTS]
❍ SECTION 1. GENERAL
•SERVICINGPRECAUTIONS................................................. 1-2
•ESDPRECAUTIONS....................................................... 1-4
• SERVICE INFORMATION FOR EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
•
HOW TO UPDATE AUDIO MICOM & DVD PROGRAMS. .
........................1-6
•SPECIFICATIONS......................................................... 1-7
❍ SECTION 2. ELECTRICAL PART
•TROUBLESHOOTINGGUIDE................................................ 2-1
• DETAILS AND WAVEFORMS ON SYSTEM TEST AND DEBUGGING . . . . . . . . . . . . . . . 2-14
•WIRINGDIAGRAM ....................................................... 2-27
•OVERALLBLOCKDIAGRAM ............................................... 2-29
•CIRCUITDIAGRAMS...................................................... 2-31
•CIRCUITVOLTAGECHART................................................ 2-59
•PRINTEDCIRCUITDIARGAMS ............................................. 2-63
❍ SECTION 3. EXPLODED VIEWS
• CABINET AND MAIN FRAME SECTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
• DECK MECHANISM EXPLODED VIEW (DP-15A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
•PACKINGACCESSORYSECTION............................................ 3-5
•SPEAKERSECTION....................................................... 3-6
❍ SECTION 4. MECHANISM (DP-15A) ....................................... 4-1
❍ SECTION 5. REPLACEMENT PARTS LIST ................................. 5-1

1-2
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 cot-
ton 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
SECTION 1. GENERAL

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 or humidity is high, where strong magne-
tism 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
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.
Resistor
(1 M Ω)Conductive
Sheet
Resistor
(1 M Ω)
Armband

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 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
SERVICE INFORMATION FOR EEPROM
POWER ON
DVD LOGO Status (NO Disk status)
Remote control
Pause key→1→4→7→2 in order.
Press number 0~9, Press character
A~F (1~6 for a while)
Use arrow key (
▲
▲
▲
▲
) to move
to appropriate position and make
changes
Press pause key once
Change will be applied when power
OFF→ON.
NAME
OPT 1
OPT 2
OPT 3
OPT 4
OPT 5
OPT 6
OPT 7
OPT 8
OPT 9
OPT A
HEX
DETECT NEW EEPROM
(OPTION EDIT SCREEN)
F1
00
C8
C9
00
0D
F0
20
C3
00

1-6
HOW TO UPDATE AUDIO MICOM & DVD PROGRAMS
1. How to update AUDIO MICOM program.
[Update using CD]
1. Change the filename to download as “(MODEL NAME)_(Version).HEX”. Only upper cases are permitted.
ex) HT904 : “HT904_0810010.HEX”
2. Copy the file to the root folder of a CD and burn it.
3. Insert the CD to the SET, and move to the DVD function. Then the upgrade process will be started with
the upgrade information.
4. If the upgrade process is complete, the set will be rebooted with “Complete” message.
[Update using USB]
1. Change the filename to download as “(MODEL NAME)_(Version).HEX”. Only upper cases are permitted.
ex) HT904 : “HT904_0810010.HEX”
2. Copy the file to the root folder of USB storage.
3. Put the USB into the SET, and move to the USB function. Then the upgrade process will be started with
the upgrade information.
4. If the upgrade process is complete, the set will be rebooted with “Complete” message.
2. How to update DVD program.
[Update using CD]
1. Rename the filename to download as “LOGO_MODELNAME.ROM” in upper cases.
ex) HT904 : “LG_HT904.ROM”
2. Copy the file to CD, and burn it.
3. Insert the CD to the SET, then after a while the CD tray will be opened with upgrade information on the
screen.
4. Remove the CD, and press “PLAY” key in remote controller.
5. Remove and reconnect the power cable when it changes to logo screen from upgrade information.
Then the upgrade process is completed.
[Update using USB]
1. Rename the filename to download as “LOGO_MODELNAME.ROM” in upper cases.
ex) HT904 : “LG_HT904.ROM”
2. Copy the file to the formatted USB, and burn it.
3. Move to the USB function, and insert the USB to the set.
The upgrade information will be shown on the screen.
4. Remove the USB, press PLAY key of the remote controller.
5. Remove and reconnect the power cable when it changes to logo screen from upgrade information. Then
the upgrade process is completed.

1-7
SPECIFICATIONS
GENERAL
Power supply Refer to main label.
Power consumption Refer to main label.
Net Weight 3.9 kg
External dimensions (W x H x D) 430 x 73 x 327 mm
Operating conditions Temperature 5°C to 35°C, Operation status: Horizontal
Operating humidity 5% to 85%
Laser Semiconductor laser, wavelength 650 nm
TUNER
FM
FM Tuning Range 87.5 - 108.0 MHz
FM Intermediate Frequency 128 kHz
AM [MW]
AM Tuning Range 552 - 1,620 kHz or 520 - 1,720 kHz or 522 - 1,710 kHz
AM Intermediate Frequency 45 kHz
AMPLIFIER
Stereo mode 155 W + 155 W (4 Ωat 1 kHz, THD 10 %)
Surround mode Front: 155 W + 155 W (THD 10 %)
Center*: 155 W
Surround*: 155 W + 155 W (4 Ωat 1 kHz, THD 10 %)
Subwoofer*: 225 W (3 Ωat 30 Hz, THD 10 %)
SPEAKERS (SH94TA)
Front Speaker Rear Speaker
SH94TA-F SH94TA-S
Type 2 Way 3 Speaker 2 Way 3 Speaker
Impedance 4 Ω4 Ω
Rated Input Power 155 W 155 W
Max. Input Power 310 W 310 W
Net Dimensions (W x H x D) 290 x 1150 x 290mm 290 x 1150 x 290mm
Net Weight 4.3 kg 4.0 kg
Center Speaker Passive Subwoofer
SH94TA-C SH94TA-W
Type 2 Way 3 Speaker 1 Way 1 Speaker
Impedance 4 Ω3 Ω
Rated Input Power 155 W 225 W
Max. Input Power 310 W 450 W
Net Dimensions (W x H x D) 350 x 105 x 93 mm 216 x 405 x 360 mm
Net Weight 1.5 kg 7.3 kg
(* Depending on the sound mode
settings and the source, there may
be no sound output.)

1-8
SPEAKERS (SH94PA)
Front Speaker Rear Speaker
SH94PA-F SH94PA-S
Type 2 Way 3 Speaker 1 Way 1 Speaker
Impedance 4 Ω4 Ω
Rated Input Power 155 W 155 W
Max. Input Power 310 W 310 W
Net Dimensions (W x H x D) 290 x 1150 x 290mm 96 x 240 x 108 mm
Net Weight 4.3 kg 0.8 kg
Center Speaker Passive Subwoofer
SH94PA-C SH94PA-W
Type 2 Way 3 Speaker 1 Way 1 Speaker
Impedance 4 Ω3 Ω
Rated Input Power 155 W 225 W
Max. Input Power 310 W 450 W
Net Dimensions (W x H x D) 350 x 105 x 93 mm 216 x 405 x 360 mm
Net Weight 1.5 kg 7.3 kg
SPEAKERS (SH94SA)
Front/Rear Speaker Center Speaker Passive Subwoofer
SH94SA-S SH94SA-C SH94SA-W
Type 1 Way 1 Speaker 1 Way 1 Speaker 1 Way 1 Speaker
Impedance 4 Ω4 Ω 3 Ω
Rated Input Power 155 W 155 W 225 W
Max. Input Power 310 W 310 W 450 W
Net Dimensions (W x H x D) 96 x 240 x 108 mm 350 x 105 x 93 mm 216 x 405 x 310 mm
Net Weight 0.8 kg 0.9 kg 5.42 kg
Designs and specifications are subject to change without prior notice.

2-1
TROUBLESHOOTING GUIDE
1. Power Supply Circuit
SECTION 2. ELECTRICAL PART
YES
Check power plug and power
supply circuit.
NO
Check power supply circuit.
NO
Check laser circuit.
NO
Check focus circuit.
Check disc.
Check tracking servo circuit.
NO
Check audio circuit.
NO
Is the Digitron on correctly?
YES
Is power on?
YES
Does initial read work?
YES
Does it play?
YES
Does it output
audio?
YES
YES
Turn power on.
Insert power cord.
OK

2-2
2. Front circuit (1/2)
Reconnect it.
NO
YES
YES YES
NO Check if
CN301 (or CN304)
and PN301 are ok?
(*1)
Red LED turn off?
NO
Refer to SMPS part.
NO
YES
NO Check if the front
power is ok?(*2)
YES
Is the Digitron on
correctly?
NO
Check pattern and resoldering
NO
Check if
DIS301 is ok?
YES
Check if the remote
control is ok?
YES
Check if all
buttons are ok?
Power on.
Front B/D ok.
1
2
*1 : CN301 : WITH I-POD DOCKING
CN304 : W/0 I-POD DOCKING
*2 : PN106 Pins.
PIN1 : -34 VKK, PIN2 : -28 FL+, PIN3 : -32 FL-,
PIN12 : +5.6VA, PIN13 : +5V

2-3
2. Front circuit (2/2)
1
Refer to power(SMPS).
NO
Replace R345~R350, R149.
NO
Check if the
power part of the
front is ok?
YES
Check if
R345~R350, R149 are
ok?
YES
Refer to MICOM circuit.
2
Refer to power(SMPS).
NO
Check if the
power part of the front
is ok?
YES
Refer to MICOM circuit.
NO
Check if the remote
control waveform of CN301 (or CN304)
pin11 is ok?
YES
Check RM circuit
NO
Check if RC01
voltage is ok(5V)?
YES
Resolder or Replace RC01.

2-4
3. I-pod circuit
Refer to Front Circuit.
NO
YES
YES YES
NO Check CN3C1 & FFC
Cable connection.
(*3)
Does it detect ipod?
Check Connector Status.
NO
YES
Does it play?
Check IC3C4.
NO
YES
Does it change?
YES
Does it output
Video/Audio?
I-pod Insert
OK
Reconnect or Resoldering.
Check CN301 & FFC
Cable Connection.
NO
*3: CN3C1 Pins.
Pin1 : 5V
Pin16, 17 : 5.6VA

2-5
4. System operation flow
YES
YES
YES
Tray closed?
1. Initializes SERVO, DSP & RISC registers.
2. Write RISC code to SDRAM.
3. Reset RISC.
Show LOGO.
Tray close to closed position.
SLED at inner
side?
Recieve
OPEN/ CLOSE
Key?
Receive
CLOSE Key?
SLED moves to inner position.
1. Judge whether have disc and disc type.
2. Jump to related disc reading procedure.
1. Execute Pressed Key & IR Key.
2. System operation routine loop.
NO
NO
NO
NO
YES
1. Stop Playback & Open Tray.
2. Display tray open message & LOGO.
POWER ON.

2-6
5. Test & debug flow
Check the POWER PART.
NO
Check the POWER PART.
NO
YES
Check the
AC voltage Power PCBA (110V
or 220V).
Check the regulators or diode.
NO
1. Check 27MHz system clock.
2. Check system reset circuit.
3. Check FLASH R/W enable signal PRD,
RWR.
4. Check FLASH Memory related circuit.
NO
Replace FLASH.
NO
YES
Are the
DC Voltage outputs OK? (-34V, -28V, -32V, ±12V,
3.5V, 5.6VA, 5V, 7V).
YES
Are 3.3V and
5V DC outputs normal on main
PCBA?
YES
YES
Update
FLASH successfully?
YES
Switch on the Power PCBA.
TEST.
A

2-7
NO
Check connection lines
between FLASH & MT1389MH
and the FLASH access time
whether is suitable or not.
NO
YES
YES
YES
YES
Check AV cable
connection to TV set.
YES
YES
YES
Flash
Memory operates
properly?
Check connection lines
between SDRAM(IC503) &
MT1389MH and the SDRAM
is damaged.
NO
SDRAM
works properly?
Check the related circuit of
MT1389MH IC501 Pins138,
142, 144, 145.
NO
MT1389MH
VIDEO outputs
properly?
Show LOGO?
NO Check the load OPEN &
CLOSE switch.
NO
Check AV cable connection
between main PCBA and
loader. (MECHA)
YES
YES
YES
Normal
OPEN_SW,
CLOSE_SW
signal?
Check the Tray control IO pins
on MT1389MH.
NO
Normal
TROPEN & TRCLOSE
signal?
Check the Tray control MOTOR
& SERVO circuit IC400.
NO
Normal
LOAD+ & LOAD-
signal?
Does Tray
move inside when it
is not at closed
position?
Power On.
A
B

2-8
NO Check the connection line of
M_STBY.
NO
YES
YES
YES
Check the cable connection
with MECHA.
Do not put in disc
and close tray.
YES
YES
YES
Motor
Driver M_STBY
pin is high?
Check the related circuit of
SLD.
NO
Motor
Driver M_STBY
pin is High?
Check the amp circuit on
motor driver.
NO
SLED+ and
SLED- output
properly?
Does
the SLED move to inner
side when it is at outer
position?
NO Check Focus connection on
MT1389MH and motor driver.
NO
Check cable connection with
pick-up head.
YES
YES
Proper
Focus outputs
to motor driver?
Check the amp circuit on motor
driver.
NO
Proper F+ & F-
outputs?
Optical Lens
has movements for
searching Focus?
B
C

2-9
NO
NO
Check the laser power circuit
on MT1389MH and
connecting to power
transistor.(Q403, Q405)
YES
YES
YES
YES
YES
YES
Check cable connection
between transistor output and
pick-up head.
Laser off.
Check the RF connection
between AM5890 and MT1389MH.
YES
YES
DVDLD or
CDLD output
property?
Check the related circuit on
laser power transistor.
NO
NO
Collector
voltage of power transistor
is OK?(Q403, Q405)
Laser
turns on when
reading disc?
Put disc in?
Check the cable connection
between spindle and main
PCB.
YES
YES
Check the spindle control amp
circuit of motor driver.
SPNP
& SPNN output
properly?
NO Check the SPINDLE related
circuit on MT1389MH.
Proper
SPINDLE signal on
MT1389MH.
Does spindle rotate?
NO Check the related circuit on
MT1389MH RF signal.
NO
NO
NO
Proper
RF signal on
MT1389MH.
Disc ID is correct?
C
D

2-10
Check connections between
MT1389MH and pick-up head.
Check the related circuit on
MT1389MH CD_DVDCT.
Check the related circuit on
MT1389MH.
Check the TRACK connection
on MT1389MH and motor driver.
Check the tracking control amp
circuit on motor driver.
NO NO
YES
YES
YES
Check CD_DVDCT connection
between AM5890 and
MT1389MH.
Check cable connection
on pick-up head.
YES
YES
Proper
signals on A, B, C,
D of MT1389MH.
NO
Proper
CD_DVDCT signal on
MT1389MH.
Focus on ok?
NO
Disc Playback?
NO NO
NO
NO
YES
Proper
CD_DVDCT signal on
MT1389MH.
YES
Proper
TRACK signal
on MT1389MH.
YES
T+ & T- output
properly?
Track On OK?
D
YES
E
Check RF signal waveform.

2-11
NO Check connection between
IC601 BCK, LRCK, ADATA0,
ADATA1, ADATA2(Pins19, 20,
23, 24, 25).
YES
YES
Check Digital Amp circuit
(IC701, IC702, IC703, IC704).
YES
Check the related circuit of
PWM.(Check Audio out
Pins 54, 55, 58, 59, 61, 62, 67,
68, 70, 71, 74, 75)
NO
NO
YES
PWM IC
received correct data
stream?
Normal
PWM IC out?(IC601).
Normal Audio
output when disc
playback?
E
TEST END.