LG 42LH20FD (CHASSIS:LT91A) 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
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.
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4. Module Specification
No.
Item
Specification
Remark
1.
Display Screen Device
42 Wide Color Display Module
LCD
2.
Aspect Ratio
16:9
3.
LCD Module
42” TFT LCD HD, 60Hz
LGD (FHD/60Hz)
4.
Operating Environment
Temp.: 0 ~ 50°C 240h
Humidity : Ta=40°C, 90% RH, 240h
42-LGD (FHD/60Hz)
5.
Storage Environment
Temp.: -20 ~60°…240h
42-LGD (FHD/60Hz)
6.
Input Voltage
AC100 ~ 240V,50/60Hz
7.
Power Consumption
Typ : 167.8W
LCD(Module)+Backlight(Lamp)
8.
Module Size
983.0 (H)x 576.0 (V)x 46.0 (D)
Without inverter
9.
Pixel Pitch
0.227 (H)x 0.681(V)
10.
Back Light
EEFL
11.
Coating
3H, Anti-glare
1. Application Range
This specification sheet is applied to the LCD TV used LT91A
chassis.
chassis.
2. Specification
Each part is tested as below without special appointment
1) Temperature : 25 ± 5°C (77 ± 9ºF), CST : 40 ± 5ºC
2) Relative Humidity : 65 ±10%
3) Power Voltage : Standard input voltage
2) Relative Humidity : 65 ±10%
3) Power Voltage : Standard input voltage
(100-240V@ 50/60Hz)
* Standard Voltage of each products is marked by models
* 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 BOM.
accordance with BOM.
5) The receiver must be operated for about 20 minutes prior to
the adjustment.
3. Test method
1) Performance : LGE TV test method followed.
2) Demanded other specification
2) Demanded other specification
- Safety : UL, CSA, IEC specification
- EMC : FCC, ICE, IEC specification
- EMC : FCC, ICE, IEC specification
SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement.
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1) Optical characteristics are determined after the unit has been ‘ON’ and stable in a dark environment at 25±2°C
2) Surface luminance is the luminance value at center 1-point across the LCD surface 50cm from the surface with all pixels displaying
2) Surface luminance is the luminance value at center 1-point across the LCD surface 50cm from the surface with all pixels displaying
white.
No
Item
Min.
Typ.
Max.
Remark
1
Viewing Angle
R/L/U/D
89/89/89/89
CR >10
2
Luminance
Luminance
400
500
PSM: Vivid, CSM: Cool, White: 100IRE
Variation
1.3
3
Contrast Ratio
CR
800
1200
All White, All Black
4
Color coordinate
WHITE
X
0.279
Y
0.292
RED
X
Typ.
0.637
Typ.
PSM: Vivid, CSM: Cool, White: 85 IRE
Y
-0.03
0.335
+0.03
GREEN
X
0.290
Y
0.611
BLUE
X
0.145
Y
0.062
P1
P2
P3
P4
P5
1W/4
2W/4
3W/4
1H/4
2H/4
3H/4
: Measurement position (5 point)
5. Chroma & Brightness
5.1 Module optical specifications
*** LGD module Uniformity Measurement Position ***
5.2 Chroma (PSM:Vivid, Color Temperature:Cool)
- except “RGB PC Mode PSM: Standard, Color Temperature: Medium”
** The W/B Tolerance is ±0.002 for Adjustment, but for DQA ±0.015
** The W/B Tolerance is ±0.002 for Adjustment, but for DQA ±0.015
No
Item
Min
Typ
Max
Remark
1.
Cool
White Balance, X axis
0.274
0.276
0.278
DQA : ±0.015
White Balance, Y axis
0.281
0.283
0.285
DQA : ±0.015
2.
Medium
White Balance, X axis
0.283
0.285
0.287
DQA : ±0.015
White Balance, Y axis
0.291
0.293
0.295
DQA : ±0.015
3.
Warm
White Balance, X axis
0.311
0.313
0.315
DQA : ±0.015
White Balance, Y axis
0.327
0.329
0.331
DQA : ±0.015
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No.
Specification
Remark
Resolution
H-freq(kHz)
V-freq(Hz)
1.
720x480
15.73
60.00
SDTV,DVD 480i
2.
720x480
15.63
59.94
SDTV,DVD 480i
3.
720x480
31.47
59.94
480p
4.
720x480
31.50
60.00
480p
5.
720x576
15.625
50.00
SDTV,DVD 625 Line
6.
720x576
31.25
50.00
HDTV 576p
7.
1280x720
45.00
50.00
HDTV 720p
8.
1280x720
44.96
59.94
HDTV 720p
9.
1280x720
45.00
60.00
HDTV 720p
10.
1920x1080
31.25
50.00
HDTV 1080i
11.
1920x1080
33.75
60.00
HDTV 1080i
12.
1920x1080
33.72
59.94
HDTV 1080i
13.
1920x1080
56.250
50
HDTV 1080p
14.
1920x1080
67.43/67.5
59.94/60
HDTV 1080p
7. Component Video Input (Y, C
B
/P
B
, C
R
/P
R
)
6. SET Optical Feature
6.1 General feature
(Measurement Condition:Full white/Vivid) -> Measure the black luminance after 30 seconds.
No
Item
Module
Luminance(min) C/R(min)
Remark
AV, COMPONENT,HDMI
AV, COMPONENT,HDMI
1
42 inch
LGD FHD
400 cd/m
2
900
except from the PC mode.
No
Item
Min
Inch
Power B/D P/N
Remark
1
Dynamic CR
40,000:1
42”HD
EAY57681303
HDMI 720p Full White/ Full Black Pattern
(Only HDMI mode)
6
.
2 Special feature
(Dynamic CR 50000:1) -> Measure the black luminance after 30 seconds.
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