LG 42LF75 / 42LF76 (CHASSIS:LD75B) Service Manual ▷ View online
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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
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
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. Inspect (on the circuit board copper side) the solder joints of
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).
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.
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.
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SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement.
1. General Specification
2. General specifications (LC370WU1-SL01)
No.
Item
Specification
Remark
1.
Video input applicable system
PAL-D/K, B/G, I, SECAM
2.
Receivable Broadcasting System
1) PAL/SECAM B/G
2) PAL/SECAM D/K
3) PAL I/II
4) SECAM L/L’
5) DVB-T
EU(PAL Market)
3.
RF Input Channel
VHF : E2 ~ E12
UHF : E21 ~ E69
CATV : S1 ~ S20
HYPER : S21~ S47
PAL
4.
Input Voltage
AC 100 ~ 240 V/50Hz, 60Hz
5.
Market
UK / France / Spain / Germany /
Finland / Sweden / Italy
6. Picture
Size
37
inch
37LF75
42 inch
42LF75
7.
Tuning System
FVS 100 program
PAL, 200 PR.(Option)
8.
Operating Environment
1) Temp : 0 ~ 40 deg
2) Humidity : 10 ~ 90 %
9.
Storage Environment
3) Temp : -20 ~ 50 deg
4) Humidity : 10 ~ 90 %
10.
Display
LCD Module
LPL / CMO
No
Item
Specification
Unit
Remark
1
Display area
819.36 (H) x 460.89 (V)
mm
2
Outline dimension
877 (W) x 516.8 (H) x 55.5 (D) with inverter
mm
3
Number of Pixels
1920 (H) x 1080(V)
1Pixel=3RGB Cells
4
Cell pitch
426.75um (H) x 426.75um (V)
um
G cell
5
Color arrangement
RGB stripe arrangement
6
Coating
Hard coating(3H), Anti-glare
7
Operating
Temperature
0 ~ 40
deg
Altitude
Environment
Humidity
10 ~ 90
%
– 0 to 1400feet
8
Storage
Temperature
-20 ~ 50
deg
Altitude
Environment
Humidity
10 ~ 90
%
– 0 to 4000feet
9
Back Light
20 EEFL
- 7 -
3. General specifications (LC420WU2-SLB1
4. Optical Feature (37"LCD Module)
No
Item
Specification
Unit
Remark
1
Display area
930.24 (H) x 523.26 (V)
mm
2
Outline dimension
983 (W) x 576 (H) x 51 (D) with inverter
mm
3
Number of Pixels
1920 (H) x 1080(V)
1Pixel=3RGB Cells
4
Cell pitch
484.5um (H) x 484.5um (V)
um
G cell
5
Color arrangement
RGB stripe arrangement
6
Coating
Hard coating(3H), Anti-glare
7
Operating
Temperature
0 ~ 40
deg
Altitude
Environment
Humidity
10 ~ 90
%
– 0 to 1400feet
8
Storage
Temperature
-20 ~ 50
deg
Altitude
Environment
Humidity
10 ~ 90
%
– 0 to 4000feet
9
Back Light
20 CCFL
No.
Item
Specification
Min.
Typ.
Max.
Remark
1.
Viewing Angle<CR>10>
R/L, U/D
178, 178
2.
Luminance
Luminance (cd/m2)
400
500
-100IRE Full White Pattern (255 gray)
-Picture : Dynamic (Cool)
Variation
-
1.3
MAX / MIN
3.
Contrast Ratio
CR(37")
400
600
RGB/HDMI-PC
- CR without PWM-Dimming
CR
D
(With AI)(37")
4000
5000
-Full white(100IRE)
-Full black(0IRE) pattern
-Picture : Dynamic (Cool)
-Input:TV/DTV/AV1,2,3/Comp/HDMI1,2
-CR with PWM-Dimming
4.
CIE Color Coordinates
White
Xw
Typ
0.276
Typ
- 85IRE Full White Pattern
Yw
-0.03
0.283
+0.03
(216 gray)
RED
Xr
0.618
- Picture : Dynamic (Cool)
Yr
0.333
Green
Xg
0.275
Yg
0.610
Blue
Xb
0.147
Yb
0.061
- 8 -
5. Optical Feature (42"LCD Module)
6. Special feature (Dynamic CR 10000:1)
1) Standard Test Condition
2) Surrounding Brightness Level : dark
3) Surrounding Temperature : 25±2°C
4) Warm-up Time : 30 Min
5) Input Signal : VESA XGA 60Hz
2) Surrounding Brightness Level : dark
3) Surrounding Temperature : 25±2°C
4) Warm-up Time : 30 Min
5) Input Signal : VESA XGA 60Hz
- Contrast, Brightness : Max.
- Clock/Clock Phase : accurate adjustment.
- Clock/Clock Phase : accurate adjustment.
No
Item
Min
Typ
Max
Inch
Remark
1
Dynamic CR
6000
8000
-
26
HDMI 720p Full Black Pattern
(Only HDMI mode )
7000
10000
-
32
Measure the black luminance after 30 sec.
7000
10000
-
37
System Control2’s 10% Dimming Value is ‘ON’.
7000
10000
-
42
No.
Item
Specification
Min.
Typ.
Max.
Remark
1.
Viewing Angle<CR>10>
R/L, U/D
178, 178
2.
Luminance
Luminance (cd/m2)
450
550
Variation
-
1.3
MAX / MIN
3.
Contrast Ratio
CR(42")
600
800
-Full white(100IRE)
-Full black(0IRE)
-Picture : Dynamic(Cool)
-Input:TV/DTV/AV1,2,3/Comp/HDMI1,2,3
-CR with PWM
-Dimming
CR
D
(With AI)(42")
4000
5000
RGB/HDMI-PC
-CR without PWM
- Dimming
4.
CIE Color Coordinates
White
Xw
Typ
0.276
Typ
-85IRE Full White Pattern (216 gray)
Yw
-0.03
0.283
+0.03
-Picture : Dynamic (Cool)
RED
Xr
0.618
Yr
0.3
Green
Xg
0.275
Yg
0.607
Blue
Xb
0.147
Yb
0.068
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