LG LAC-3700 Service manual
CAR CD/MP3/WMA
RECEIVER
SERVICE MANUAL
MODEL : LAC3700
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL
.
MODEL : LAC3700
SERVICE MANUAL
P/NO : AFN33777095 JUNE, 2007
http://biz.lgservice.com
CONTENTS
SECTION 1 SUMMARY
SERVICING PRECAUTIONS..........................................................................................................................................1-2
ESD PRECAUTIONS .......................................................................................................................................................1-3
SPECIFICATIONS.............................................................................................................................................................1-4
SECTION 2 ELECTRICAL
ELECTRICAL TROUBLESHOOTING GUIDE & WAVEFORMS .............................................................................2-1
1. MAIN, FRONT & TUNER PART................................................................................................................................2-1
2. CD PART.....................................................................................................................................................................2-4
• WAVEFORMS..............................................................................................................................................................2-7
INTERNAL BLOCK DIAGRAM OF ICs......................................................................................................................2-10
1. IC301 (HA13173AH) ................................................................................................................................................2-10
2. IC302 (BA00CCOWFP) ...........................................................................................................................................2-12
3. IC401 (µPD78F1164) ...............................................................................................................................................2-12
4. IC601 (BD3805F) .....................................................................................................................................................2-15
5. IC801 (TB2904HQ) ..................................................................................................................................................2-16
6. IC901 (PT6523) ........................................................................................................................................................2-17
BLOCK DIAGRAM .........................................................................................................................................................2-19
CIRCUIT DIAGRAMS.....................................................................................................................................................2-21
1. MAIN CIRCUIT DIAGRAM ......................................................................................................................................2-21
2. CDP CIRCUIT DIAGRAM........................................................................................................................................2-23
3. FRONT CIRCUIT DIAGRAM ..................................................................................................................................2-25
4. LCD LIGHTING CIRCUIT DIAGRAM.....................................................................................................................2-27
PRINTED CIRCUIT BOARD DIAGRAMS..................................................................................................................2-29
1. MAIN P.C.BOARD ....................................................................................................................................................2-29
2. CDP P.C.BOARD .....................................................................................................................................................2-33
3. FRONT P.C.BOARD ................................................................................................................................................2-34
4. LCD LIGHTING P.C.BOARD...................................................................................................................................2-35
SECTION 3 EXPLODED VIEWS
1. CABINET AND MAIN FRAME SECTION ................................................................................................................3-1
SECTION 4 REPLACEMENT PARTS LIST.............................................................4-1
1-1
SECTION 1 SUMMARY
SERVICING PRECAUTIONS
1. Always disconnect the power source before:
1) Removing or reinstalling any component, circuit board, module or any other instrument assembly.
2) Disconnecting or reconnecting any instrument electrical plug or other electrical connection.
3) Connecting a test substitute in parallel with an electrolytic capacitor in the instrument.
CAUTION: A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result in an
explosion hazard.
2. Do not defeat any plug/socket B+ voltage interlocks with which instruments covered by this service
manual might be equipped.
3. Do not apply power to this instrument and or any of its electrical assemblies unless all solid-state
device heat sinks are correctly installed.
4. Always connect a test instrument’s ground lead to the instrument chassis ground before connecting
the test instrument positive lead. Always remove the test instrument ground lead last.
1) The service precautions are indicated or printed on the cabinet, chassis or components. When servicing,
follow the printed or indicated service precautions and service materials.
2) The Components used in the unit have a specified conflammability and dielectric strength. When replacing
any components, use components which have the same ratings. Components marked in the circuit diagram
are important for safety or for the characteristics of the unit. Always replace with the exact components.
3) An insulation tube or tape is sometimes used and some components are raised above the printed writing
board for safety. The internal wiring is sometimes clamped to prevent contact with heating components.
Install them as they were.
4) After servicing always check that the removed screws, components and wiring have been installed correctly
and that the portion around the service part has not been damaged. Further check the insulation between
the blades of attachment plug and accessible conductive parts.
1-2
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 know 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 ARROWHEAD 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 INTENED TO
ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY
INFORMATION IN SERVICE LITERATURE.
1-3
SPECIFICATIONS
• GENERAL
Output Power 50W x 4CH (Max.)
Power Source DC 12V
Speaker impedance 4Ω
Ground System Negative
Dimensions (W x H x D) 180 x 51 x 171mm (Without Control Panel)
Net Weight 2.0kg
• CD SECTION
Frequency Response 20Hz ~ 20kHz
S/N Ratio 80dB
Distortion 0.12%
Channel Separation (1kHz) 55dB
• RADIO SECTION
FM
Frequency Range 65 ~ 74, 87.5 ~ 107.9 or 87.5 ~ 108MHz
S/N Ratio 53dB
Distortion 0.7%
Usable Sensitivity 12dBµV
AM (MW)
Frequency Range 520 ~ 1720 or 522 ~ 1620kHz
S/N Ratio 45dB
Distortion 1.0%
Usable Sensitivity 28dBµV
1-4
SECTION 2 ELECTRICAL
ELECTRICAL TROUBLESHOOTING GUIDE & WAVEFORMS
1. MAIN, FRONT & TUNER PART
No Symptom Check Point Location No.
SYSTEM CONTROL
1 No Power Checked the Fuse. CN801
Checked the Back up Vdd, Gnd. CN801(16,15)
Checked the Micom Back Up Vdd. IC301(14), D307, IC401(30,47,50,99,100)
Checked the Micom Ground. IC401(20,51,97,98)
Checked the Reset. IC402, IC401(90)
Checked the X-tal. X401, X402
Checked the ACC in. Q301, Q302, IC401(38), CN801(14)
Checked the detachable switch. IC401(73)
Checked the Key line. IC401(52,53)
2 Not available Remocon Checked the Remocon Sens Vdd. CN901(12), Q316, Q317, D307
Checked the Remocon Sens line. RM901(1), IC401(5)
3 Not available to Volume control Checked the Encoder Volume. EV901(1), IC401(40,41)
4 Not available to Key Control Checked Tact switch. SW901 ~ SW919
Checked Key line. IC410(52,53)
5 No sound Checked the E-VR Vdd. IC301(10), IC601(16)
Checked the E-VR Ground. IC601(1,22)
Checked the E-VR control. IC601(22,23), IC401(1,2)
Checked the E-VR Signal in/out. IC601(3,5,6,7,10,11)
IC601(12,13,14,15)
Checked the E-VR Mute Control IC601(19), IC401(6)
* Power IC Checked the Power IC Vdd. IC801(6,20)
: Refer to next page Checked the Power IC Ground. IC801(1,2,8,13,18,24)
Checked the Power IC Control. IC801(4,22), IC401(3,10)
Checked the Power IC Signal in/out. IC801(11,12,14,15)
IC801(3,5,7,9,17,19,21,23)
Checked the Power IC Mute. IC801(22)
Checked the Power IC Standby. IC801(4)
Checked the Power IC Ripple. IC801(10)
Checked the Main Connector. CN801(1,2,3,4,8,9,12,13)
6 No Line out signal Checked the E-VR Vdd. IC301(10), IC601(16)
Checked the E-VR Ground. IC601(1,22)
Checked the E-VR control. IC601(20,21), IC401(1,2)
Checked the E-VR Signal in/out. IC601(3,5,6,7,10,11)
IC601(12,13,14,15)
Checked the Line out Mute circuit Q705, IC401(48)
Check the Line out Jack CN703
8 Heard Pop Noise Checked the Mute Control. IC601(19), IC801(4, 22), IC401(3,6,10)
Checked the AF Mute. TU101(19), IC401(4)
9 Not avaliable to Telephone Mute Checked the telephone Mute Control. CN801(5), Q305, Q306, IC401(62)
Checked the Mute Control. IC601(19), IC801(4, 22), IC401(3,6,10)
10 Not avaliable to ANT(Motor Type) Control Checked the ANT Control. IC301(12,13), IC401(87)
11 Not avaliable to Remote Checked the Remote control. CN801(6), IC402(1,2,4), Q308, Q309
(External AMP) IC401(63,64)
12 No output Beep sound. Checked the Beep Control. IC401(80)
2-1
CAUTION - Tip for repair
A
Before exchange power amp IC(TB2904) for no audio problem, you have to check
below list.
1. Check VCC (pin 20, 6) & GND
2. Check input pin 11, 12, 14, 15
3. Check Standby, pin 4
: Follow the below list.
4. Check Mute function, pin 22
: Follow the below list.
Stand-by Power Sound Voltage
ON OFF OFF 0 to 1.5
OFF ON ON 3.5 to 6V
5. Check Ripple pin 10.
: Normally it is high (about 10V)
Mute Sound Voltage
ON OFF 0 to 1.5
OFF ON 3.5 to 6V
6. Re-soldering all the pin of IC.
: Prevent crack of solder line.
* Keep changed IC, We request that you send it to HQ.
C1
C1
C6
C1
C1
PRE-GND
1 20 6
TAB V
IN1
11
IN2
12
C-GND
16
IN3
15
IN4
14
13
STBYRIP
10 25 22
2
C
4
CC1VCC2
OFF-SET
DET
OUT1
()
PW-GND1
OUT1 ( )
OUT2 ( )
PW-GND2
OUT2 ( )
OUT3 ( )
PW-GND3
OUT3 ( )
OUT4 ( )
PW-GND4
OUT4 ( )
MUTE
4
C
3
5
C
C
+
9
8
7
+
5
2
3
+
17
18
-
19
+
21
24
-
23
R
1
R
L
R
L
R
L
R
L
5 V
PLAY
MUTE
: PRE-GND
: PW-GND
Picture 1) Power IC desc.
2-2
No Symptom Check Point Location No.
DISPLAY & LIGHTING
1 No Display or Checked the LCD DRV Vdd. Q322, Q316, Q317
Some Display is broken IC901(58,59)
Checked the LCD DRV Ground. IC901(60)
Checked the LCD DRV OSC. IC901(61)
Checked the LCD DRV control. IC401(75,79,85,86),
IC901(57,62,63,64)
Checked the LCD DRV to LCD Pattern.
2 No LCD Lighting or Checked the LCD Lighting VDD. Q319, Q320, Q322, IC301(4,9)
Color is different IC401(64)
Checked the LED. LD930, LD931
3 Not avaliable to LCD Lighting Checked the LCD Lighting Control. CN801(11), Q303, Q304, Q321,
control IC401(58)
Checked the LED. LD930, LD931
4 No Key Lighting Checked the LED Lighting Vdd. IC301(4,9), IC401(64)
Checked the LED. LD901 ~ LD921
5 Don't moved Level bar Checked the Level Meter control. IC401(54,57)
6 Not avaliable to Dimmer control Chekced the Dimmer control. CN801(11), Q303, Q304, IC301(4,9)
IC901(1 ~ 55)
No Symptom Check Point Location No.
TUNER FUNCTION
1 Not available to Tuner Checked the Tuner Vdd. TU101(4,16), IC301(10), IC401(39)
Q350, Q351
Checked the Tuner Ground. TU101(3, 5,10,17)
Checked the PLL data. TU101(11,12,13,14,15)
IC401(67,68,44,45,46)
Checked the RF signal in. TU101(1, 2)
Checked the S-Meter control. TU101(7)
Checked the SD & ST IND. TU101(6)
2 Tuner no sound Checked the Tuner Signal out. TU101(8,9), IC601(6,7)
Checked the AF mute. TU101(19), IC401(4)
3 Not available to RDS Checked the RDS data. TU101(20,21), IC401(65,83)
2-3
2. CD PART
Something wrong with the CD player?
No loading?
YES
A B C
Checked the CD Vdd?
YES
Checked the CD DSP ground?
YES
Checked the motor DRV
VDD?
YES
Checked the CD DSP reset?
YES
Checked the CD DSP X-tal?
YES
Checked the disc in
load switch?
NO
NO
NO
NO
NO
NO
Fig 1, 2
CN510(13, 6)
IC506(26, 32, 47, 78, 18)
IC504(7, 8, 20)
IC506(72)
X503
CN509(15)
YES
Checked the loading
motor control?
YES
Checked the 8/12cm
sens switch?
YES
OK
NO
Fig 3, 4
NO
Fig 1, 2
2-4
CN509(12, 17)
IC513(12, 14, 15)
CN509(10)
A
No reading & "FILE CHECK"
DISPLAY?
YES
Checked the limit switch?
YES
Checked the motor DRV
mute control?
YES
Checked the motor
LD control?
YES
Checked the CD DSP control?
YES
Checked the focus control?
YES
NO
Fig 1, 2
NO
NO
Fig 3, 4
NO
Fig 10, 11
NO
Fig 5
CN509(8)
CN509(16)
D5, D6
IC506(67, 68, 69, 70, 71)
IC506(25)
IC513(17, 18)
Checked the focus error
level out.(FE mon)?
YES
Checked the PLL locking.
(FSEQ)?
YES
Checked the RF signal
out check?
YES
Checked the spindle
motor control?
YES
Checked the TRVP control?
YES
Checked the tracking control?
YES
OK
NO
Fig 5
NO
Fig 9
NO
Fig 8
NO
Fig 7
NO
Fig 13
NO
Fig 6
IC506(25)
R517
IC506(54)
IC506(41, 16)
IC506(21)
IC513(8, 5)
PN504(5, 6)
IC506(24)
IC513(19, 20)
2-5
Loading...