LG 42LH70YR-ME Schematic

		Internal Use Only
North/Latin America	http://aic.lgservice.com
Europe/Africa	http://eic.lgservice.com
Asia/Oceania	http://biz.lgservice.com

LCD TV

SERVICE MANUAL

CHASSIS : LP91D

MODEL : 42LH70YR 42LH70YR-ME

CAUTION

BEFORE SERVICING THE CHASSIS,

READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CONTENTS

CONTENTS ..............................................................................................	2
PRODUCT SAFETY ..................................................................................	3
SPECIFICATION ........................................................................................	6
ADJUSTMENT INSTRUCTION................................................................	11
TROUBLE SHOOTING ............................................................................	14
BLOCK DIAGRAM...................................................................................	17
EXPLODED VIEW ...................................................................................	18
SVC. SHEET ...............................................................................................

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 2 -	LGE Internal Use Only
Only for training and service purposes

SAFETY PRECAUTIONS

IMPORTANT SAFETY NOTICE

Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the Schematic Diagram and Exploded View.

It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent Shock, Fire, or other Hazards.

Do not modify the original design without permission of manufacturer.

General Guidance

An isolation Transformer should always be used during the servicing of a receiver whose chassis is not isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician from accidents resulting in personal injury from electrical shocks.

It will also protect the receiver and it's components from being damaged by accidental shorts of the circuitry that may be inadvertently introduced during the service operation.

If any fuse (or Fusible Resistor) in this TV receiver is blown, replace it with the specified.

When replacing a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the resistor 10mm away from PCB.

Keep wires away from high voltage or high temperature parts.

Before returning the receiver to the customer,

always perform an AC leakage current check on the exposed metallic parts of the cabinet, such as antennas, terminals, etc., to be sure the set is safe to operate without damage of electrical shock.

Leakage Current Cold Check(Antenna Cold Check)

Leakage Current Hot Check (See below Figure) Plug the AC cord directly into the AC outlet.

Do not use a line Isolation Transformer during this check.

Connect 1.5K/10watt resistor in parallel with a 0.15uF capacitor between a known good earth ground (Water Pipe, Conduit, etc.) and the exposed metallic parts.

Measure the AC voltage across the resistor using AC voltmeter with 1000 ohms/volt or more sensitivity.

Reverse plug the AC cord into the AC outlet and repeat AC voltage measurements for each exposed metallic part. Any voltage measured must not exceed 0.75 volt RMS which is corresponds to 0.5mA.

In case any measurement is out of the limits specified, there is possibility of shock hazard and the set must be checked and repaired before it is returned to the customer.

Leakage Current Hot Check circuit

AC Volt-meter

To Instrument’s

Good Earth Ground such as WATER PIPE, CONDUIT etc.

exposed METALLIC PARTS

0.15uF

With the instrument AC plug removed from AC source, connect an electrical jumper across the two AC plug prongs. Place the AC switch in the on position, connect one lead of ohm-meter to the AC plug prongs tied together and touch other ohm-meter lead in turn to each exposed metallic parts such as antenna terminals, phone jacks, etc.

If the exposed metallic part has a return path to the chassis, the measured resistance should be between 1MΩ and 5.2MΩ .

When the exposed metal has no return path to the chassis the reading must be infinite.

An other abnormality exists that must be corrected before the receiver is returned to the customer.

1.5 Kohm/10W

When 25A is impressed between Earth and 2nd Ground for 1 second, Resistance must be less than 0.1 Ω

*Base on Adjustment standard

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 3 -	LGE Internal Use Only
Only for training and service purposes

SERVICING PRECAUTIONS

CAUTION: Before servicing receivers covered by this service manual and its supplements and addenda, read and follow the SAFETY PRECAUTIONS on page 3 of this publication.

NOTE: If unforeseen circumstances create conflict between the following servicing precautions and any of the safety precautions on page 3 of this publication, always follow the safety precautions. Remember: Safety First.

General Servicing Precautions

1.Always unplug the receiver AC power cord from the AC power source before;

a.Removing or reinstalling any component, circuit board module or any other receiver assembly.

b.Disconnecting or reconnecting any receiver electrical plug or other electrical connection.

c.Connecting a test substitute in parallel with an electrolytic capacitor in the receiver.

CAUTION: A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result in an explosion hazard.

2.Test high voltage only by measuring it with an appropriate high voltage meter or other voltage measuring device (DVM, FETVOM, etc) equipped with a suitable high voltage probe.

Do not test high voltage by "drawing an arc".

3.Do not spray chemicals on or near this receiver or any of its assemblies.

4.Unless specified otherwise in this service manual, clean electrical contacts only by applying the following mixture to the contacts with a pipe cleaner, cotton-tipped stick or comparable non-abrasive applicator; 10% (by volume) Acetone and 90% (by volume) isopropyl alcohol (90%-99% strength)

CAUTION: This is a flammable mixture.

Unless specified otherwise in this service manual, lubrication of contacts in not required.

5.Do not defeat any plug/socket B+ voltage interlocks with which receivers covered by this service manual might be equipped.

6.Do not apply AC power to this instrument and/or any of its electrical assemblies unless all solid-state device heat sinks are correctly installed.

7.Always connect the test receiver ground lead to the receiver chassis ground before connecting the test receiver positive lead.

Always remove the test receiver ground lead last.

8.Use with this receiver only the test fixtures specified in this service manual.

CAUTION: Do not connect the test fixture ground strap to any heat sink in this receiver.

Electrostatically Sensitive (ES) Devices

Some semiconductor (solid-state) devices can be damaged easily by static electricity. Such components commonly are called

Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field-effect transistors and semiconductor "chip" components. The following techniques should be used to help reduce the incidence of component damage caused by static by static electricity.

1.Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging wrist strap device, which should be removed to prevent potential shock reasons prior to applying power to the

unit under test.

2.After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.

3.Use only a grounded-tip soldering iron to solder or unsolder ES devices.

4.Use only an anti-static type solder removal device. Some solder removal devices not classified as "anti-static" can generate electrical charges sufficient to damage ES devices.

5.Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ES devices.

6.Do not remove a replacement ES device from its protective package until immediately before you are ready to install it. (Most replacement ES devices are packaged with leads electrically shorted together by conductive foam, aluminum foil or comparable conductive material).

7.Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material to the chassis or circuit assembly into which the device will be installed.

CAUTION: Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.

8.Minimize bodily motions when handling unpackaged replacement ES devices. (Otherwise harmless motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity sufficient to damage an ES device.)

General Soldering Guidelines

1.Use a grounded-tip, low-wattage soldering iron and appropriate tip size and shape that will maintain tip temperature within the range or 500°F to 600°F.

2.Use an appropriate gauge of RMA resin-core solder composed of 60 parts tin/40 parts lead.

3.Keep the soldering iron tip clean and well tinned.

4.Thoroughly clean the surfaces to be soldered. Use a mall wirebristle (0.5 inch, or 1.25cm) brush with a metal handle.

Do not use freon-propelled spray-on cleaners.

5.Use the following unsoldering technique

a.Allow the soldering iron tip to reach normal temperature. (500°F to 600°F)

b.Heat the component lead until the solder melts.

c.Quickly draw the melted solder with an anti-static, suctiontype solder removal device or with solder braid.

CAUTION: Work quickly to avoid overheating the circuit board printed foil.

6.Use the following soldering technique.

a.Allow the soldering iron tip to reach a normal temperature (500°F to 600°F)

b.First, hold the soldering iron tip and solder the strand against the component lead until the solder melts.

c.Quickly move the soldering iron tip to the junction of the component lead and the printed circuit foil, and hold it there only until the solder flows onto and around both the component lead and the foil.

CAUTION: Work quickly to avoid overheating the circuit board printed foil.

d.Closely inspect the solder area and remove any excess or splashed solder with a small wire-bristle brush.

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 4 -	LGE Internal Use Only
Only for training and service purposes

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.

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.

2.Draw away the melted solder with an anti-static suction-type

solder removal device (or with solder braid) before removing the IC.

Replacement

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 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 leads extending from the circuit board and crimp the "U" with 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 board.

4.Insert new transistor in the circuit board.

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 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

the two "original" leads. If they are not shiny, reheat them and if necessary, apply additional solder.

Fuse and Conventional Resistor 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.

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.

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).

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.

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.

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.

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.

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.

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 5 -	LGE Internal Use Only
Only for training and service purposes

SPECIFICATION

NOTE : Specifications and others are subject to change without notice for improvement.

1.	Application range	3. Test method
This spec sheet is applied to LCD TV used LP91A chassis.		1)	Performance: LGE TV test method followed
		2)	Demanded other specification
2.	Specification		- Safety: CE, IEC specification
			- EMC : CE, IEC

Each part is tested as below without special appointment.

1)Temperature : 25±5ºC (77±9ºF), CST : 40±5ºC

2)Relative Humidity : 65±10%

3)Power Voltage : 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 BOM.

5)The receiver must be operated for about 5 minutes prior to the adjustment.

4.Electrical specification

4.1 General Specification

No	Item		Specification		Measurement	Remark
1	Screen Size	42” wide Color Display Module				Resolution:1920*1080
2	Aspect Ratio	16:9
3	LCD Module	42” TFT WUXGA LCD				FHD
4	Operating Environment	Temp.: 0 ~ 40 deg
		Humidity : 0 ~ 80 %
5	Storage Environment	Temp.: -20 ~ 60 deg
		Humidity : 0~ 85 %
6	Input Voltage	AC100-240V~, 50/60Hz
		≤ 250 W		42” FHD, 100Hz
7	LDC Module	FHD		965.2x558.2x33
	(Maker : LGD)			0.4845 x 0.42675
		Coating			3H

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 6 -	LGE Internal Use Only
Only for training and service purposes

5. Chroma& Brightness (Optical)

5.1. LCD Module

the Color Coordinates check condition

-50cm from the surface, Full White Pattern

-Picture mode Vivid

No.	Item			Min.	Typ.	Max.	Unit	Maker	Remark
1.	Luminance			400	500		cd/m2
	(W/O PC mode)
2.	VIew angle (R/L, U/D)				178/ 178		degree	LGD	CR > 10
3.	Color Coordinates	White	Wx	Typ	0.279	Typ			LGD 42”(FHD)
			Wy	-0.03	0.292	+0.03			LC420WUD-SBT1
		RED	Xr		0.637				(100Hz/Slim)
			Yr		0.335
		Green	Xg		0.290
			Yg		0.606
		Blue	Xb		0.145
			Yb		0.062
4.	Contrast ratio			1000:1	1400:1				LGD 42”(FHD)
5.	Luminance Variation					1.3

6. Component Video Input (Y, PB, PR)

No			Specification			Remark
	Resolution		H-freq(kHz)	V-freq(Hz)	Pixel Clock(MHz)
1	720* 480		15.73	59.94	13.500	SDTV, DVD 480I( 525I)
2	720* 480		15.75	60.00	13.514	SDTV, DVD 480I( 525I)
3	720* 576		15.625	50.00	13.500	SDTV, DVD 576I( 625I) 50Hz
4	720* 480		31.47	59.94	27.000	SDTV 480P
5	720* 480		31.50	60.00	27.027	SDTV 480P
6	720* 576		31.25	50.00	27.000	SDTV 576P 50Hz
7	1280*	720	44.96	59.94	74.176	HDTV 720P
8	1280*	720	45.00	60.00	74.250	HDTV 720P
9	1280*	720	37.50	50.00	74.25	HDTV 720P 50Hz
10	1920*	1080	28.125	50.00	74.250	HDTV 1080I 50Hz,
11	1920*	1080	33.72	59.94	74.176	HDTV 1080I
12	1920*	1080	33.75	60.00	74.25	HDTV 1080I
13	1920*	1080	56.25	50	148.5	HDTV 1080P
14	1920*	1080	67.432	59.94	148.350	HDTV 1080P
15	1920*	1080	67.5	60.00	148.5	HDTV 1080P

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 7 -	LGE Internal Use Only
Only for training and service purposes

7.RGB

9.1Analog PC, RGBDTV –NOT SUPPORT

No			Specification			Remark
	Resolution		H-freq(kHz)	V-freq(Hz)	Pixel Clock(MHz)
1	640*	350	31.468	70.09	25.17	EGA
2	720*	400	31.469	70.09	28.32	DOS
3	640*	480	31.469	59.94	25.17	VESA( VGA)
4	800*	600	37.879	60.317	40	VESA( SVGA)
5	1024* 768		48.363	60.004	65	VESA( XGA)
6	1280* 768		47.776	59.87	79.5	VESA( WXGA)
7	1360* 768		47.72	59.799	84.75	VESA( WXGA)
8	1280*	1024	63.668	59.895	109.00	XGA	Only FHD Model
9	1920*	1080	66.587	59.934	138.50	WUXGA(Reduced Blanking)	Only FHD Model

8.HDMI Input

8.1PC –Spec. out but it can be shown the picture at only HDMI/ DVI IN 1 via DVI to HDMI Cable)

No	Resolution			H-freq(kHz)		V-freq.(Hz)			Pixel clock(MHz)		Proposed		Remark
1	640 x 480			31.469		59.94			25.17		VESA( VGA)
2	800 x 600			37.879		60.317			40.00		VESA( SVGA)
3	1024 x 768			48.363		60.004			65.00		VESA( XGA)
4	1280 x 768			47.776		59.87			79.5		VESA( WXGA)
5	1360 x 768			47.72		59.799			84.62		VESA( WXGA)
6	1366 x 768			47.7		60.00			84.62		WXGA
7	1280 x 1024			63.595		60.00			108.875		SXGA
8	1920 x 1080			66.647		59.988			138.625		WUXGA
8.2 DTV Mode
No				Specification							Remark
	Resolution			H-freq(kHz)		V-freq(Hz)		Pixel Clock(MHz)
1	720 x	480		15.73		59.94		13.500		SDTV, DVD 480I(525I)
2	720 x	480		15.75		60.00		13.514		SDTV, DVD 480I(525I)			Spec. out
3	720 x	576		15.625		50.00		13.500		SDTV, DVD 576I(625I) 50Hz			but display.
4	720 x	480		31.47		59.94		27		SDTV 480P
5	720 x	480		31.5		60.00		27.027		SDTV 480P
6	720 x	576		31.25		50.00		27		SDTV 576P
7	1280 x 720			44.96		59.94		74.176		HDTV 720P
8	1280 x 720			45		60.00		74.25		HDTV 720P
9	1280 x 720			37.5		50.00		74.25		HDTV 720P
10	1920 x	1080		28.125		50.00		74.25		HDTV 1080I
11	1920 x	1080		33.72		59.94		74.176		HDTV 1080I
12	1920 x	1080		33.75		60.00		74.25		HDTV 1080I
13	1920 x	1080		56.25		50.00		148.5		HDTV 1080P
14	1920 x	1080		67.432		59.94		148.350		HDTV 1080P
15	1920 x	1080		67.5		60.00		148.5		HDTV 1080P
16	1920 x	1080		27		24.00		74.25		HDTV 1080P
17	1920 x	1080		33.75		30.00		74.25		HDTV 1080P

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 8 -	LGE Internal Use Only
Only for training and service purposes

ADJUSTMENT INSTRUCTION

1. Application Range

This specification sheet is applied to all of the LCD TV, LP91A/B/C/D chassis.

(2)Download steps

1)Execute ‘ISP Tool’ program, the main window(Mstar ISP utility Vx.x.x) will be opened

2)Click the “Connect” button and confirm “Dialog Box”

2.Specification

1)Because this is not a hot chassis, it is not necessary to use an isolation transformer. However, the use of isolation transformer will help protect test instrument.

2)Adjustment must be done in the correct order.

3)The adjustment must be performed in the circumstance of 25 ±5 °C of temperature and 65±10% of relative humidity if there is no specific designation.

4)The input voltage of the receiver must keep 100~220V, 50/60Hz.

5)Before adjustment, execute Heat-Run for 5 minutes at RF no signal.

3.Adjustment items

3.1.PCB assembly adjustment items

(1)Download the MSTAR main software (IC800, Mstar ISP Utility)

1)Using D/L Jig

2)Using USB Memory Stick.

(2)ADC Calibration – RGB / Component

(3)Input Tool-Option/Area option.

(4)Check SW Version.

4. PCB assembly adjustment method

4.1. Mstar Main S/W program download

4.1.1.Using D/L Jig

(1)Preliminary steps

1)Connect the download jig to D-sub(RGB) jack

- LH70

3)Click the “Config.” button and Change speed I2C Speed setting : 350Khz~400Khz

4) Read and write bin file.

Click “(1)Read” tab, and then load download file(XXXX.bin) by clicking “Read”.

1

Filexxx.bin

Copyright © 2009 LG Electronics. Inc. All right reserved.	- 9 -	LGE Internal Use Only
Only for training and service purposes