Service Manuals, User Guides, Schematic Diagrams or docs for : LG TV pc73a_cf25a64_cf28a64
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Troubleshooting Guide
NO RASTER
Check +B voltage
at D825 Cathode.
Normal Abnormal
Is the voltage at pin8 and Check Open
37 of IC501 8V? No Fuse of AC line.
Check/replace
Check the in/output
Yes OK Fuse, D801 and
of IC607.
IC801.
Check pin40 of Check the voltage of 0V
No IC501 (H-Out). C808.
OK
Check the IIC Bus
Check/replace Check/replace
Yes Line (SDA,SCL) pin3 254~380V
IC501. R801 and D801.
and 4 of IC501.
Check Q451 Check the voltage Lower than 6V
No Collector waveform. at pin9 of IC801.
Check D802,
Check/replace Q451,
Yes D805, D807, Q801
T451 and R452.
and IC801.
Check Q452 Check/replace
Collector waveform. IC803, D824 and D835.
No
Check/replace
Q452. Yes
Check T401 &
each pin voltage.
NO SOUND
(PICTURE OK)
AM NO SOUND NICAM,FM NO SOUND
No Check Sound No
Select correct Check L System Select correct
system in MENU
system in MENU is right? system in MENU.
OSD.
Yes Yes
Check the logic of Check the AM Check demodulated Check the logic of OK Check Z103,
pin3 and 15 of Line. SIF signal (pin26 of pin3 and 15 of Q102
IC101. Abnor (pin27 of IC101) IC101). Not IC101. & pin25 of IC101.
mal OK
Normal Normal Not OK
Not OK
Check AM Input of Check Check C607 Check pin14
IC601, pin44. pin47 of IC601. Not & R601. & 25 of IC01.
OK
Not OK
OK OK
Normal
Check/replace Check/replace
Z104 & +B of pin14 & 25 of Check X601 & pin16 Not OK Check/replace
IC101. IC01. and 46 of IC601, IIC
X601 and IC601.
Bus Line.
OK OK
Check R, L input Not OK Check R,L Out
of IC651, pin2 and
of IC601.
5.
OK Not OK
Check +B of
Is any OSD
IC651
displayed?
& D822.
NO PICTURE
NO SOUND
Is any OSD displayed?
No Yes Check receiving system in
Go to
MENU & excute Auto-
NO RASTER (SOUND OK).
programme.
Go to Does the Auto-programme
NO SOUND. operate properly?
Not OK
Direct Input channel number
Yes & store in manual-program
MENU.
Go to NO SOUND
Not OK Check 5V, 12V,
PICTURE OK. And Check 5V, 12V, 33V & 33V
IIC Bus Line of TUNER. & IIC Bus Line.
OK
OK Is the CVBS signal
OK (pin 14 of IC101).
Not OK
OK
Check pin9 and 18 of
MICOM IC01.
Not OK
OK Check IC01 &
H-Sync Line.
NO RASTER
(SOUND OK)
Check the
Heater voltage of CPT(6-6.5Vrms).
OK OK Not OK
Check Check
Check
HV,SCREEN voltage of the HEATER pulse of FBT
lk Current of IC501,pin18.
CPT. T401.
OK Not OK
OK Check/replace OK Check Check
CPT Board components. FR405,FR901 & P402. FBT T401.
Not OK Not OK
Check/replace Check
FBT T401. P501,ZD564 & IC501.
NO PICTURE
NO COLOR
Is the CVBS signal at pin14 of
IC101 normal? No
Check Receiving system in
Yes MENU & go to NO PICTURE,
NO SOUND.
Is the CVBS signal at pin16 of
IC201 normal? No
Check the state of pin11 and 13
Yes of IC201,L201 and R206(+B of
IC201).
Is the CVBS signal at pin 13 of
IC501 normal? No
Check/replace
Yes
Q201,L603(12V) & CVBS Line.
Is the CVBS signal at pin 2 of
IC702 normal? No
Check pin9 of IC501, IC702
Yes
IIC Bus Line & Q701.
Is the CVBS signal at pin11 of No
IC501 normal?
Yes
Is the Y signal at pin 27 of
IC501 normal? No
Check IC502, L542
Yes
& pin26 of IC501.
Check if R-Y and B-Y signal of
pin32 and 33 of IC501 are
No
normal?
Check X501, IC503, L541,
ZD541 & IC504(In case of
SECAM system).
NO TELETEXT
Check the voltage of OK Check CVBS signal at pin2 Not OK Check/replace Q701, X701
pin7, 16 and 21 of IC701. of IC702 & X701. & IC501.
0V OK
Check 5V & 12V Supply OK Check IC701, 702 & IIC Bus
Line of IC701 and 702. Line (SDA, SCL).
And check pin803B & Power
Line (MAIN2 PCB).
ADJUSTMENT INSTRUCTIONS
System Frequency Modulation Output level Adjust
YSafety Precautions B/G/SECAM-L 38.9MHz OFF 10mVp-p L107
1. It is safe to adjust after using insulating transformer
SECAM-L' 33.9MHz OFF 10mVp-p VR102
between the power supply line and chassis input to
prevent the risk of electric shock and protect the
instrument. (Table 1)
2. Never disconnect leads while the TV receiver is on.
3. Don't short any portion of circuits while power is on.
4. The adjustment must be done by the correct appliances. T SECAM-L' Adjustment
But this is changeable in view of productivity.
5. Unless otherwise noted, set the line voltage to NOTE : This adjustment should be performed after PIF
230Vac!10%, 50Hz. adjustment.
YTest Equipment required Test Point : TP1
1. RF signal generator (with pattern generator)
2. DC Power Supply Adjust : VR102
3. Multimeter (volt meter)
4. Oscilloscope 1) Turn on S1 and S3 and off S2.
5. Color analyzer 2) Adjust VR101 so that the DC voltage may be indicated
3.1!0.1Vdc.
Main Board(Component side view)
V Multimeter or Oscilloscope
Power- 1
Supply
IC01
5V JP7 IC05
8V JP4 IC102 TP1 24 Signal-
103pF Generator
5V 6 JP1 38.9MHz
L107 33.9MHz
10 JP2
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