LG DT-7000 Manuale utente
SERVICE MANUAL
LG DT-7000
MODEL
NO TELETEXT
NO RASTER
(SOUND OK)
Check the voltage
of ZD701 (5V)
Abnormal Normal
NG
NG
NG NG
Check the 5V line
to be correct. Check if the video signal is
at pin 10 of IC702. Check the
CVBS line.
Check/Replace
IC702, 703, X701.
Check I2C BUS lines.
(SDA, SCL)
Check pin 51, 52, 53 and 54
of IC702.
Check the voltage of
CPT Heater
Check the voltage of
HV and SCREEN of CPT.
Check/Replace
CPT Board.
Check the Heater pulse
at pin 9 of T701.
Check/Replace
T701.
Check/Replace
T701.
Check/Replace
Connector, FR459 and FR901.
Check/Replace IC503.
NO PICTURE/NO COLOR
Is the CVBS signal at pin 14
of IC101 normal? Check/Replace
IC101.
Is the CVBS signal at pin 26
of IC501 normal? Check/Replace
Q201.
Is the R-Y, B-Y signal at pin 3, 4
of IC501 normal? Check/Replace
IC501, 502.
Is the Y, U, V(in, 50Hz) signal at
pin 12, 13 and 14 of IC501 normal? Check/Replace
IC101.
Is the Y, U, V(out, 100Hz) signal at
pin 3, 4 and 6 of P101 normal? GO to
DIGITAL BLOCK.
Is the R, G, B signal at
pin 1, 3 and 5 of IC501 normal? Check/Replace
IC503.
Check/Replace
IC503.
NG
NG
NG
NG
NG
NG
NO SOUND
(PICTURE OK)
(NO AM Sound)
Check the Audio signal
at pin27 of IC101.
Check/Replace
IC101
Check the Audio signal
at pin55 of IC601.
(NO FM/NICAM Sound)
Check if the SIF signal at pin26 of
IC101 normal.
Check/Replace
IC101.
Are the Audio signal at pin28 and
29 IC601 normal?
Are the Audio signal at pin 2 and
5 of IC605 normal?
Are the Audio signal at pin 7 and
11 of IC605 normal?
Check/Replace
Connectors and Speakers.
Check/Replace
X601, IC601 and IC606.
Check LO, ROlines.
Check/Replace
IC605, Sound +B Line.
Check AM line
NG
NG
NG
NG
NG
NG
NO PICTURE/NO SOUND
(RASTER OK)
Is the Auto programme
operation normal?
Is the CVBS signal at pin14
of IC101 normal?
yes
yes OK
OK
no
no
no
Go to NO PICTURE Block.
NO SOUND Block
Check the voltages
5V, 12V and 33V of Tuner.
Check/Replace
ZD101, 102,
5V, 12V and 33V Lines.
Check/Replace
IC101.
Check I2C bus lines.
(SDA, SCL)
Check/Replace TUNER.
NO RASTER
NO SOUND
Check +B voltage at J306.
Is there the square waveform at
pin4 of P101 (H-out)
140V
yes
yes
yes
OK
230~380V
Lower than 6V
no
NG
0V
no
Is the waveform at the collector of
Q402 normal?
Check/Replace
T701 and CONNECTORS.
Is the voltage at pin 24
of IC01 5V?
Check/Replace IC803,
D826, 827, 828, 829, T805,
T801, 804 and Fuse (FC02).
Check the part of
Digital PCB ASSY
Check the voltage of C834.
Check the voltage at pin9
of IC801.
Check/Replace
D802, D803, Q801 and
IC801.
Check/Replace
D801.
no
Check/Replace
Q401, T401and Q402.
Check/Replace
IC802, IC804, D810 and R832.
Digital assy Trouble shooting
Check with Color Bar signal input.
Check the circuit from PQ101
to CQ54,57
Replace an IC causing Power
drop.
Check ICQ501.
Replace ICQ05
Replace ICQ04
Replace ICQ09
Replace ICQ08
Replace ICQ07
Replace ICQ02
Check Deflection Part
Replace ICQ01
Replace IC501
Replace ICQ06
Check IC503
No Picture or
screen flows
Check Y,U,V signal
input of PQ101.
Check Y,U,V
signals at CQ54(+),CQ57(+)
and CQ58(+).
Check the Vcc
of each IC.
Check Pin 34~40 and
Pin 48~51 of ICQ05.
Check Pin10 of ICQ06
Check Pin15 and
16 of ICQ06 for 27MHz and
13.5MHz waveform.
Check the Video
Sync at CQ54(+).
Check if Pin13 and 20
of ICQ01 have 32¥s?
Check Pin61~68 and
Pin2~5 of ICQ04
Check Pin13~16, Pin18~21,
Pin22~25 of ICQ02.
Check the outputs
of Pin 2,4,5 of PQ102.
no no
no
no
no good
no good
Pin13~16 no signal
Pin18~21
no signal
Pin22~25
no signal
no signal
Yes
No Picture
Screen flows
good
no good
no good
no good
good
Yes
good
Yes
good
good
Yes
Yes
Yes
* VCO (Voltage Controlled Oscillation) Adjustment
a) For B/G system
1) Turn on DC power supplies.
2) Adjust VCO adjust coil(L107)so that DMM reads 2.5Vdc+_0.1V.
Preparation for VCO Adjustment
1. Connect the measuring equipment to the TV as shown in Fig. 1.
2. Set RF output level of sweep S.G.(Signal Generator) to 80dBuV.
3. Set Alignment Scope, Volts/Div to 100mV, AC/DC switch to
AC, Line/Ext switch to Ext.
IC101
TDA4474
C123(+)
Multimeter &
oscilloscope
2.5Vdc
SW1
SW2
24
34 5 L107
J169 5V
GND
AM/FM SW
L/L'SW
Z101
G3962
J77
12Vdc
R124
C25(+)
R139
C25(-)
Power
Supply
GND(C26(-))
38.9MHz
Signal
generator
GND
Ceramic
CAP.
10000pF
Ceramic
CAP.
10000pF
MAIN BOARD
Fig.1: Connection Diagram of Equipment for BG VCO Adjustment
Test Poin t :Pin 24 of IC101 (+ lead of C123)
Adjust :L107
b) For Secam-L' system
1) Turn on DC power supplies.
2) Apply 5Vdc to the + lead of C25.
3) Adjust VCO adjust volume(VR102) so that the DMM reads 2.5Vdc+_0.1V.
* Screen voltage adjustment
1) Tune the TV set to receive digital pattern.
2) Press PSM button on the Remote Controller to get the STANDARD picture.
3) Turn the screen VR of FBT until the black level of picutre signal is 150Vdc at the digital pattern.
IC101
TDA4474
C123(+) GND(C122(-))
Multimeter &
oscilloscope
2.5Vdc
SW1
SW2
24
34 5 VR102
J139 GND
5V
AM/FM SW
L/L'SW
Z102
G3953
J77
12Vdc
R124
C25(+)
R169
C25(-)
Power
Supply
GND(C26(-))
33.9MHz
Signal
generator
GND
Ceramic
CAP.
10000pF
Ceramic
CAP.
10000pF
MAIN BOARD
Fig. 2 : Connecting Diagram of Equipments for secam-L' system.
Test Poin t : J5 (one lead of R533)
Adjus t : VR102
GND
CPT BOARD
OSCILLSCOPE
Rk
BLACK Level
150Vdc 1.5V
Fig. 3 Fig. 4
* RF AGC (Auto Gain Control) Adjustment
The RF AGC contro l(VR101)was aligned at the time of manufacture for optimum performance over a wide range
conditions. Readjust of VR101 should not be necessary unless unusual local conditions exist, such as ;
1) Channel interference in a CATV system
2) Picture bending and/or color beats, which are unusually due to excessive RF signal input when the receiver is too close
to a transmitting tower or when the receiver is connected to an antenna distribution system where the RF signal has
been amplified.
In this case, the input signal should be attenuated (with pad or filter) to a satisfactory level.
3) Picture noise caused by “broadcast noise” or weak signal.
If the broadcast is “clean” and the RF signal is at least 1mV (60dBu), the picture will be noise free in any area.
Adjusting th eVR101 (RF AGC)control to one end of rotation will usually cause a relatively poor signal to noise ratio;
Adjusting to the other end of rotation will usually cause a degradation of over load capabilities resulting in color beats or
adjacent channel reference.
For best results, adjust VR101 control while performing on all other local channels, or the voltage at J173 will be 6.0+_0.1Vdc.
(RF level: 60dBuV).
* Focus Adjustment
NOTE : This adjustment should be performed after warming up for 10 minutes.
1) Set color & brightness to minimum, contrast to 50% respectively.
2) Input the PAL BG Digital Pattern signal.
3) Adjust the Focus control for best overall focus.
Test Poin t : J173 or Observing Display
Adjus t : VR101
J173
6Vdc
AGC TP. VR101
(AGC ADJ.)
Digital
Multimeter
MAIN BOARD
TUNER
Fig. 5
Test Poin t : Observing Display
Adjus t : Focus control of FBT
Indice
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