LG 42LB7DF (CHASSIS:LJ81A) Service Manual ▷ View online
- 5 -
IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat against the
circuit foil. When holes are the slotted type, the following technique
should be used to remove and replace the IC. When working with
boards using the familiar round hole, use the standard technique
as outlined in paragraphs 5 and 6 above.
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat against the
circuit foil. When holes are the slotted type, the following technique
should be used to remove and replace the IC. When working with
boards using the familiar round hole, use the standard technique
as outlined in paragraphs 5 and 6 above.
Removal
1. Desolder and straighten each IC lead in one operation by gently
1. Desolder and straighten each IC lead in one operation by gently
prying up on the lead with the soldering iron tip as the solder
melts.
melts.
2. Draw away the melted solder with an anti-static suction-type
solder removal device (or with solder braid) before removing the
IC.
IC.
Replacement
1. Carefully insert the replacement IC in the circuit board.
2. Carefully bend each IC lead against the circuit foil pad and
1. Carefully insert the replacement IC in the circuit board.
2. Carefully bend each IC lead against the circuit foil pad and
solder it.
3. Clean the soldered areas with a small wire-bristle brush.
(It is not necessary to reapply acrylic coating to the areas).
"Small-Signal" Discrete Transistor
Removal/Replacement
1. Remove the defective transistor by clipping its leads as close as
Removal/Replacement
1. Remove the defective transistor by clipping its leads as close as
possible to the component body.
2. Bend into a "U" shape the end of each of three leads remaining
on the circuit board.
3. Bend into a "U" shape the replacement transistor leads.
4. Connect the replacement transistor leads to the corresponding
4. Connect the replacement transistor leads to the corresponding
leads extending from the circuit board and crimp the "U" with
long nose pliers to insure metal to metal contact then solder
each connection.
long nose pliers to insure metal to metal contact then solder
each connection.
Power Output, Transistor Device
Removal/Replacement
1. Heat and remove all solder from around the transistor leads.
2. Remove the heat sink mounting screw (if so equipped).
3. Carefully remove the transistor from the heat sink of the circuit
Removal/Replacement
1. Heat and remove all solder from around the transistor leads.
2. Remove the heat sink mounting screw (if so equipped).
3. Carefully remove the transistor from the heat sink of the circuit
board.
4. Insert new transistor in the circuit board.
5. Solder each transistor lead, and clip off excess lead.
6. Replace heat sink.
5. Solder each transistor lead, and clip off excess lead.
6. Replace heat sink.
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as
1. Remove defective diode by clipping its leads as close as
possible to diode body.
2. Bend the two remaining leads perpendicular y to the circuit
board.
3. Observing diode polarity, wrap each lead of the new diode
around the corresponding lead on the circuit board.
4. Securely crimp each connection and solder it.
5.
5.
Inspect (on the circuit board copper side) the solder joints of
the two "original" leads. If they are not shiny, reheat them and if
necessary, apply additional solder.
necessary, apply additional solder.
Fuse and Conventional Resistor
Removal/Replacement
1. Clip each fuse or resistor lead at top of the circuit board hollow
Removal/Replacement
1. Clip each fuse or resistor lead at top of the circuit board hollow
stake.
2. Securely crimp the leads of replacement component around
notch at stake top.
3. Solder the connections.
CAUTION: Maintain original spacing between the replaced
component and adjacent components and the circuit board to
prevent excessive component temperatures.
component and adjacent components and the circuit board to
prevent excessive component temperatures.
Circuit Board Foil Repair
Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
board causing the foil to separate from or "lift-off" the board. The
following guidelines and procedures should be followed whenever
this condition is encountered.
Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
board causing the foil to separate from or "lift-off" the board. The
following guidelines and procedures should be followed whenever
this condition is encountered.
At IC Connections
To repair a defective copper pattern at IC connections use the
following procedure to install a jumper wire on the copper pattern
side of the circuit board. (Use this technique only on IC
connections).
To repair a defective copper pattern at IC connections use the
following procedure to install a jumper wire on the copper pattern
side of the circuit board. (Use this technique only on IC
connections).
1. Carefully remove the damaged copper pattern with a sharp
knife. (Remove only as much copper as absolutely necessary).
2. carefully scratch away the solder resist and acrylic coating (if
used) from the end of the remaining copper pattern.
3. Bend a small "U" in one end of a small gauge jumper wire and
carefully crimp it around the IC pin. Solder the IC connection.
4. Route the jumper wire along the path of the out-away copper
pattern and let it overlap the previously scraped end of the good
copper pattern. Solder the overlapped area and clip off any
excess jumper wire.
copper pattern. Solder the overlapped area and clip off any
excess jumper wire.
At Other Connections
Use the following technique to repair the defective copper pattern
at connections other than IC Pins. This technique involves the
installation of a jumper wire on the component side of the circuit
board.
Use the following technique to repair the defective copper pattern
at connections other than IC Pins. This technique involves the
installation of a jumper wire on the component side of the circuit
board.
1. Remove the defective copper pattern with a sharp knife.
Remove at least 1/4 inch of copper, to ensure that a hazardous
condition will not exist if the jumper wire opens.
condition will not exist if the jumper wire opens.
2. Trace along the copper pattern from both sides of the pattern
break and locate the nearest component that is directly
connected to the affected copper pattern.
connected to the affected copper pattern.
3. Connect insulated 20-gauge jumper wire from the lead of the
nearest component on one side of the pattern break to the lead
of the nearest component on the other side.
Carefully crimp and solder the connections.
CAUTION: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
of the nearest component on the other side.
Carefully crimp and solder the connections.
CAUTION: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
- 6 -
SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement.
4. General Specification(TV)
1. Application range
This specification is applied to LJ81A chassis.
2. Requirement for Test
Testing for standard of each part must be followed in below
condition.
condition.
(1) Temperature : 20 ± 5°C, CST : 40± 5°C
(2) Humidity : 65% ± 10%
(3) Power : Standard input voltage (100-240V~, 50/60Hz)
(2) Humidity : 65% ± 10%
(3) Power : Standard input voltage (100-240V~, 50/60Hz)
*Standard Voltage of each products is marked by models.
(4) Specification and performance of each parts are followed
each drawing and specification by part number in
accordance with SBOM.
accordance with SBOM.
(5) The receiver must be operated for about 20 minutes prior
to the adjustment.
3. Test method
3.1 Performance : LGE TV test method followed
3.2 Demanded other specification
3.2 Demanded other specification
Safety : UL, CSA, IEC Specification
EMC
EMC
: FCC, ICES, IEC
Chassis
LJ81A
42LB7DF-SB
Central and
South AMEROCA
LG
Model Name
Market
Brand
Remark
Model Name
42LB7DF-SB
Central and
South AMEROCA
Safety : IEC/EN60065
EMC : CISPR13
Market
Appliance
Receiving System
Available Channel
Input Voltage
Market
Screen Size
Aspect Ratio
Tuning System
Module
Operating Environment
Storage Environment
1) SBTVD / NTSC / PAL-M / PAL-N
1) VHF : 02~13
2) UHF : 14~69
3) DTV : 02-69
4) CATV : 01~135
1) AC 100 ~ 240V 50/60Hz
Central and South AMERICA
42 inch Wide (1366 x 768)
42 inch Wide (1920 x 1080)
16:9
FS
LC420WU6-SLA1
1) Temp : 0 ~ 40 deg
2) Humidity : ~ 80 %
1) Temp : -20 ~ 60 deg
2) Humidity : ~ 85 %
1
2
3
4
5
6
7
8
9
No
HD
FULL HD
FULL HD
42LB7DF-SB
Model
Specification
Option
Remark
- 7 -
No
1
2
3
4
5
Item
White brightness
(Center 1-point/Full white Pattern)
Brightness uniformity
Color coordinate
RED
X
Y
GREEN
X
Y
BLUE
X
Y
WHITE
X
Y
Color coordinate uniformity
Contrast ratio
Color Temperature
Cool
Standard
Warm
Color Distortion, DG
Color Distortion, DP
Color S/N, AM/FM
Color Killer Sensitivity
Min
400
80
700:1
7000:1
Typ.
-1000
43.0
-80
Typ
500
0.638
0.340
0.279
0.611
0.146
0.062
0.272
0.278
1000:1
10000:1
11000
9300
6500
Unit
cd/m
2
%
Typ.
+0.03
%
deg
dB
dBm
Max
Typ.
+1000
10.0
10.0
Remark
42LB7DF-SB
Full white
N/A
NORMAL
DCR
<Test Condition>
HDMI Input,
85% Full white pattern
5. Chroma & Brightness
6. Component Video Input (Y, CB/PB, CR/PR)
Typ-0.03
Typ+0.03
720*480
720*480
720*480
720*480
1280*720
1280*720
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
1920*1080
15.73
15.73
31.47
31.47
45.00
44.96
33.75
33.72
67.500
67.432
27.000
26.97
33.75
33.71
56.25
28.125
60
59.94
60
59.94
60.00
59.94
60.00
59.94
60
59.939
24.000
23.94
30.000
29.97
50.000
25.000
13.5135
13.5
27.027
27.0
74.25
74.176
74.25
74.176
148.50
148.352
74.25
74.176
74.25
74.176
148.5
74.25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SDTV ,DVD 480I
SDTV ,DVD 480I
SDTV 480P
SDTV 480P
HDTV 720P
HDTV 720P
HDTV 1080I
HDTV 1080I
HDTV 1080P
HDTV 1080P
HDTV 1080P
HDTV 1080P
HDTV 1080P
HDTV 1080P
HDTV 1080P
HDTV 1080P
Resolution
No
H-freq(kHz)
V-freq(kHz)
Pixel clock
Proposed
- 8 -
No
Resolution
H-freq(kHz)
V-freq.(Hz)
Pixel clock(MHz)
Proposed
PC
DDC
1
640*350
31.468
70.09
25.17
EGA
X
2
720*400
31.469
70.08
28.32
DOS
O
3
640*480
31.469
59.94
25.17
VESA(VGA)
O
4
640*480
37.861
72.80
31.50
VESA(VGA)
O
5
640*480
37.500
75.00
31.50
VESA(VGA)
O
6
800*600
35.156
56.25
36.00
VESA(SVGA)
O
7
800*600
37.879
60.31
40.00
VESA(SVGA)
O
8
800*600
48.077
72.18
50.00
VESA(SVGA)
O
9
800*600
46.875
75.00
49.50
VESA(SVGA)
O
10
1024*768
48.363
60.00
65.00
VESA(XGA)
O
11
1024*768
56.476
70.06
75.00
VESA(XGA)
O
12
1024*768
60.023
75.02
78.75
VESA(XGA)
O
13
1280*768
47.776
59.870
79.5
CVT(WXGA)
O
14
1280*768
60.289
74.893
102.25
CVT(WXGA)
O
15
1360*768
47.712
60.015
85.50
VESA (WXGA)
O
16
1280*1024
63.981
60.020
108.00
VESA (SXGA)
O
17
1280*1024
79.976
75.025
135
VESA (SXGA)
O
18
1600*1200
75.00
60.00
162
VESA (UXGA)
O
19
1920*1080
67.5
60
148.5
HDTV 1080P
O
7. RGB Input (PC)
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