LG CHASSIS PV-71A User manual

SERVICE MANUAL
LG CHASSIS PV-71A
MODEL

1
Is there about 6V
at pin 9 of P804?
YES
Is there about 11V
at '+' terminal
of C856?
YES
Is there about 6.1V
at pin 9 of IC801?
YES
Is there voltage at
pin 9 of T801?
YES
NO POWER : NO STAND-BY
Replace the Fuse
Check the 6V Line
of MAIN 1 BOARD
Check if the
Fuse is O.K.?
YES
NO
Check/Replace
D801, D802, 803, 804, R801, C807.
NO
Check/Replace
D806, Q801, R807, ZD801, C814,
IC801.
NO
¡Check/Replace FR851, D852,
C856, Q860, Q861, Q862,
ZD860, ZD861, R874.
¡Check the pin 11 of P804 :
'LOW"
NO
Check/Replace
R863, IC857, D858, R877, C875
NO
TROUBLE SHOOTING

2
Is there about 115V
at '+' terminal of C865?
YES
Is there about
6V at pin 9 of P804?
YES
NO POWER : NO MONITOR ON
Go to NO POWER (NO ST-BY)
BLOCK
Go to NO RASTER BLOCK
Check T701, Q781 and go to
NO RASTER BLOCK
Check the
NO POWER(NO ST-BY)
BLOCK
YES
NO
Check the pin 10 of P804 ; "HIGH"
NO
¡Check/Replace D851, L851,
C860, IC851.
¡Check the pin 10 of P804 :
'HIGH"
NO

3
Is there about
6.3VAC at HEATER of CPT
SOCKET?
YES
Does the waveform
appear at the collector
of Q781?
YES
Does the square
waveform appear at pin 1 of
P805?
YES
Is there about 8V
at pin 6 of P805?
YES
NO RASTER
Go to NO POWER BLOCK
Go to NO PICTURE BLOCK
Is there about 115V
at pin 3 of T701?
YES
NO
¡Check/Replace F852, D850,
C857, R899, IC853, C863.
¡Check the 8V LINE of VCD
BOARD
NO
¡Check the H-OUT LINE of VCD
BOARD.
¡Check/Replace IC501 of VCD
BOARD.
NO
Check/Replace Q782, T781, R783,
R787, Q781.
NO
Check/Replace T701, 5PIN
CONNECTOR, FR2901, FR2902
(14" : FR1901)
NO

4
Is there about
44V at pin 6 of IC701?
YES
Is there about
15V at pin 3 of
IC701?
YES
V. Deflection ERROR
Check the vertical part of VCD
BOARD
Check/Replace IC701
Does the V-A, V-B
signal appear at pin 4, 7
of P805?
YES
NO
Check/Replace FR702, D702, C704,
L731
Check;/Replace FR701, D701, C708,
L732, C734.
NO
Is there about
200V at pin 1 of P2901B?
(14" : P1901B)
YES
NO PICTURE
Check the CVBS line of VCD BOARD
(Refer to VCD BLOCK DIAGRAM)
¡Check/Replace IC2901.
(14" : IC1901)
¡Check screen voltage
Does the RGB signal
appear at pin 3, 5, 7 of
P2902? (14" : P1902)
YES
NO
Check/Replace FR704, D703, C702,
T701, 5PIN CONNECTOR, L2901,
R2924 (14" : L1901, R1924)
NO
NO

5
Does the sound
signal appear at pin 4
of IC601?
YES
Does the sound
signal appear at pin 9
of P805?
YES
NO SOUND
Check/Replace FR854, D855, IC601.
Check/Replace speaker,
speaker connector.
Is there about
25V at pin 5
of IC601?
YES
NO
Check the Audio source line of
VCD BOARD
¡Check the voltage at collector of
Q601.
¡Check/Replace IC601, external
components of IC601.
NO
NO

2-2
EXPLODED VIEW
102
913
170 150 153 511
103
112
520
501
603
604
640
650
660
601
602
620
630
610
A20
A00
P851
400 20"
400
943
943
14"
350
330
340 320
315
310
360
300
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120
14"
350
120
330
340 320
315
310
360
300
20"

2-3
EXPLODED VIEW PART LIST The components identified by shading and
mark are critical for safety.
Replace only with part number specified.
LOCA. NO PART NO DESCRIPTIONS
102 341-721E HOLDER,D-COIL(FOR SAFA,L=65)
103 341-721F HOLDER,D-COIL(FOR SAFA,L=130)
112 2055-V1221B CPT A48QAD220X 03N7ND(+0.4) 20"
2055-V0744D CPT A34KPU02XX 31N7ND(+0.4) 14"
120 120-C93G SPEAKER,GENERAL C091P06K1459 8OHM 5/ 20"
120-101B SPEAKER,C080P17-54PK14 14"
150 150-D02M COIL,DEGAUSSING,CU 20" 60T 15OHM
150-D02B COIL,DEGAUSSING,CU 14" 42T 5.7OHM
153 153-276A DY DCAM1-20PLAA 20"
153-113V DY DCAD2-14SNAB 14"
170 170-851B LEAD SET ASSY,CPT EARTH(L=640) 20"
170-851A LEAD SET ASSY,CPT EARTH(L=460) 14"
300 3091V00057E CABINET ASSY,KI-20U72X KPLKU,LG (SILVER)
3091V00064A CABINET ASSY,KI-14U71
315 315-740H DOOR,FOR TVCR
310 5020V00118A BUTTON,CONTROL 20"
5020V00137A BUTTON,CONTROL 14"
320 4970V00001A SPRING,CST DOOR(2880)
330 320-075B SPRING,KNOB 20"
320-075R SPRING,COIL 14"
340 5020V00116A BUTTON,POWER MAIN 20"
5020V00135A BUTTON,POWER MAIN 14"
350 5020V00119A BUTTON,CH/VOL 20"
5020V00138A BUTTON,CH/VOL 14"
360 5020V00117A BUTTON,POWER SUB 20"
5020V00136A BUTTON,POWER SUB 14"
400 3809V00043E BACK COVER ASSY,KI-20U72 KPLKU
3809V00043F BACK COVER ASSY,KI-20U71 KPLKU
3809V00076E BACK COVER ASSY,KI-14U71 KPLKU
501 4810V00012A BRACKET,SMPS(27DECK)
511 6620VBC001A SOCKET,CPT 29.1 PHI SINGLE(PCS629-03A) 20"
381-100F SOCKET,CPT 022.5 S/LESS(PCS625-11) 14"
520 6871VDM027A PWB ASSY,MAIN2 PV-71A 20INCH(SMPS/CPT)
6871VDM027E PWB ASSY,MAIN2 PV-71A 20INCH(SMPS/DEF)
6871VDM027F PWB ASSY,MAIN2 PV-71A 14INCH
601 4810V00062B BRACKET,MAIN 1 ASSY SUS SPUUPRTER
602 4814V00016A SHIELD,BOTTOM
603 4814V00015A SHIELD,TOP 20"
4814V00015D SHIELD,VCR ASSY SBHG1-A 14"
604 4980V00014A SUPPORTER,YC,VCD PCB
610 6871VMM065B PWB ASSY,MAIN1, PV71A(I/I,2T,W/TXT)
6871VMM065N PWB ASSY,MAIN1, PV71A(I/I,1T,W/O TXT)
6871VMM065M PWB ASSY,MAIN1, PV71A(I/I,1T,W/TXT)
620 6871VSM094B PWB ASSY,Y/C PV71A,(W/O SECAM), M/I
630 6871VSM121B PWB ASSY,EXTRA SUB PV71A ETC (2T,B/G,I/
6871VSM121C PWB ASSY,A/V PV71A (1T,B/G,I/I)
640 6871VSM095C PWB ASSY,VCD PV71A 20" (I/I,TXT),M/I
6871VSM095F PWB ASSY,VCD PV71A 20" (I/I,W/O TXT)
6871VSM203G PWB ASSY,VCD PV71A 14" (I/I,W/O TXT)
6871VSM203A PWB ASSY,VCD/TXT 14"
650 6871VSM122B PWB ASSY,PV71A, TUNER2(I/I) ,M/I
660 6871VSM070A PWB ASSY,KEY BOARD MV-64A
913 332-057B SCREW ASSY,HEXAGON HEAD 20"
332-057A SCREW ASSY,HEXAGON HEAD 14"
943 1PPF0403116 SCREW,PAN HEAD D4 L16
A00 145-001H DECK ASSY,TV27A20P183B(6731RTV005B)
A20 146-001B HOUSING ASSY,D27S(VIDEO (219-023A))
P851 174-225E CORD ASSY,POWER UK,224A
" 174-225K CORD ASSY,POWER UK L4=100

3-5
ADJUSTMENT INSTRUCTIONS
Notes;
(Adjustments must be performed by the following procedures)
1. It is recommended that an isolation transformer be used
when servicing this chassis to prevent electric shock and
damage to test equipment.
2. The ac line voltage must be maintained at 230 vac, +- 10%,
50/60 hz.
3. Prior to making any adjustments, the receiver must be
operated for 10 minutes.
1. DECK ADJUSTMENT
1. Deck Transit System Adjustment
1-1. Necessary Instruments
1)TAPE for SP (4HD), Normal (2HD)
2)Oscilloscope
3)10:1 Probes 2EA
4)Adjustment Driver
(P2, P3, X-distance (NUT), Audio (NUT) control)
5)RMS Meter (Audio Level Meter)
1-2.Preliminary Steps
1) Connect CH 1 of the oscilloscope to J439 (H/SW) on the
main PCB. Trigger on this channel.
2)Connect CH 2 of the oscilloscope to J218 (RF) on the main
PCB. Monitor this waveform when preceding with step 4.
3)Play an alignment tape.
4)When the "auto Trk" caption appears on screen, press the
TRK up (+) button on the RCU to initialize the manual
tracking feature.
5) If manual tracking differs from auto tracking, precede with
steps 1-3 (RF Linearity) and 1-4 (X-Distance Adj.).
1-3. RF linearity check and adjustment
1)Adjust P2 & P3 so that the RF ENVELOPE waveform is
maximum and stabilized .
2)Check if the ENVELOPE waveform is at its maximum size
by pressing TRK UP(+) and DOWN(-) button one step.
1-4. X-Distance Adjustment
1)Turn the Cone Screw of the DECK left or right so that the
RF waveform is maximum.
2)Check if the RF waveform satisfies the linearity by
pressing TRK UP(+) and DOWN(-) button one step.
CAUTION:If the RF waveform becomes maximum with
the Cone Screw more than 2 turns, its out of adjustment.
(2 turns; 720)
1-5. Audio Level Check and Adjustment
1)Connect "+" terminal of RMS Meter (Audio Level Meter)
to J233 on MAIN PCB AUDIO OUT and "-" terminal to
GND, respectively.
2)Play the 1khz and 7khz segments on the alignment tape
and confirm if the spec is meet in item #3. If not adjust
the azimuth screw to meet this spec.
3)Audio Level Spec: 1KHz ; 0.5 +_0.1Vrms
6KHz ; 1K +_1.5dB
2. CIRCUIT ADJUSTMENT
1. PG Adjustment
1-1. Necessary Instruments
1)Alignment tape SP
2)Oscilloscope
3)10 : 1 Probe
1-2.Adjustment
1)PLAY exclusive use of SP tape. (2HD: NORMAL TAPE)
2)Connect CH 1 of the Oscilloscope to J439 (H/SW) on the
MAIN PCB and VOL/DIV to 1V Range and Trigger the
Oscilloscope.
3)Connect CH 2 of the oscilloscope to J454 (Video Out) on
the main PCB and set the VOL/DIV to 500mV Range.
4)Set TIME/DIV of oscilloscope to 50us Range.
5) Adjust VR01 so that V-sync Falling Edge of Video signal
become 412usec+_20usec.
DRUM
P2
FE HEAD
P1
ARM
TENSION
P0
SUPPLY
REEL TAKE-UP REEL
PINCH
ROLLER
TAPE
CAPSTAN
T/UP
ARM
P4
A/C
HEAD
P3 X-DISTANCE
ADJUST SCREW
AZIMUTH
SCREW CONE POINT
SCREW
A/C HEAD
HEIGHT ADJUST NUT
<Adjust Parts Location>
P2 POST ADJUST
P2
P3
P3 POST ADJUST
<Adjustment waveform>
Adjust waveform
<Adjustment Waveform>

3-6
2. Normal REC Bias Level Adjustment
2-1. Necessary Instruments
1) Blank tape for Recording
2)RMS Meter
2-2. Adjustment
1) Set the TV/VCR to A/V input mode.
2)Insert a tape and press REC button.
3)Connect RMS Meter's (+), (-) to R401 on MAIN PCB.
4)Adjust VR401 so that the RMS Meter's indicator become
within 2.6mV+_0.05mV.
3. Focus Voltage Adjustment
1)Receive the cross hatch pattern.
2)Press the PICTURE button to set the Standard ON
condition.
3)Adjust Focus control knob so that the focus of center &
circumference to be best.
4. Screen Adjustment
1)Press TV/AV button and select AV mode.
2)Adjust SCREEN control until the retrace line is visible and
return until the retrace line is invisible.
*HHHHoooowwwwttttooooggggeeeettttiiiinnnnttttooooSSSSVVVVCCCCmmmmooooddddeeeewwwwhhhheeeennnnyyyyoooouuuuddddoooonnnn''''tttthhhhaaaavvvveeeeSSSSVVVVCCCC
RRRReeeemmmmooootttteeeeCCCCoooonnnnttttrrrroooolllllllleeeerrrr....
PPPPuuuusssshhhhtttthhhheeee""""OOOOKKKK""""KKKKeeeeyyyyoooonnnntttthhhheeeeuuuusssseeeerrrr''''ssssRRRReeeemmmmooootttteeeeCCCCoooonnnnttttrrrroooolllllllleeeerrrraaaannnnddddllllooooccccaaaallll
""""OOOOKKKK""""bbbbuuuuttttttttoooonnnnaaaatttttttthhhheeeessssaaaammmmeeeettttiiiimmmmeeee....
5. VCO Adjustment
1)Select channel 0.
2) Input PAL Digital pattern (175.25MHz).
3)Press SVC Key on the Service Remote Controller to get
into SVC mode and press PR +/- Key to select VCO.
4)Press VOL +/- Key until OK is displayed on the screen.
6. LCO Adjustment
1)Select channel 99.
2) Input SECAM-L' pattern (55.75MHz).
3)Press SVC Key on the Service Remote Controller to get
into SVC mode and Press PR +/- Key to select LCO.
4)Press VOL +/- Key until OK is displayed on the screen.
7. RF AGC Adjustment
1)Input PAL DIGITAL PATTERN.
2)Connect DMM to AGC(J232) test point on the Main PCB.
3)Press SVC Key on the Service Remote Controller to get
into SVC mode and press PR +/- Key to select AGC.
4) Press VOL +/- Key until DMM reads the data on the table
below.
NNNNooootttteeee::::When adjusting 2 TUNER Model, select BOOSTER OFF
from MENU.
8. White Balance Adjustment
1)Input a signal which lower half is black and upper half is
white.
2) Set the picture at standard on.
3)Press SVC Key on the Service Remote Controller to get
into Service mode.
4)Press PR +/- Key to select BG, RG.
Press VOL +/- Key until X=281+_3, Y=288+_3.
*GG is fixed data at 32 so, do not adjust GG data.
9. Deflection Data Adjustment
1)Input PAL Digital Pattern.
2)Press SVC Key on the Service Remote Controller and
select LINE SERVICE 2 mode.
3)Press PR +/- Key to select an adjustment mode.
4) Press VOL +/- Key to adjust data.
5) Vertical SLOPE adjustment
a) Select V-SLP mode with PR +/- Key.
b) Press VOL +/- Key until the horizontal center line of
the large circle coincides with Blanking Line.
6) Vertical amplitude adjustment
a) Select V-AMP mode with PR +/- Key.
b) Press VOL +/- Key until the upper and lower end of the
large circle reach 5 mm inside from the effective area
of CPT.
7) Vertical Shift Adjustment
a) Select V-SFT mode with PR +/- Key.
b) Press VOL +/- Key until the horizontal center coincides
with the vertical sign slot mark of CPT.
8) Horizontal Shift Adjustment
a) Select H-SFT mode with PR +/- Key.
b) Press VOL +/- Key until the vertical center coincides
with the horizontal sign slot mark of CPT.
9) Vertical S-Correction Adjustment
a) Select S-COL mode with PR +/- Key.
b) Press VOL +/- Key until the grid of Cross Hatch
Pattern is even all over the screen.
Adjust Period
<Adjust Waveform>
* CAUTION:Set the trigger mode of Oscilloscope to DC.
MODEL
2 TUNER
Electric fields strength
AGC Voltage
Electric fields strength
AGC Voltage
70dBu 1dBu
5.5 0.1Vdc
65dBu 1dBu
5.6 0.1Vdc
1 TUNER
KL/KB/KI