LG 42PG20 Service Manual
LG TRAINING MANUAL
LG TRAINING MANUAL
Fall 2008 PDP Training
42PG20
- 4 -
Ph o n e Co n t a C t s :
Contact Number Hours of Operation
Customer Service (800) 243-0000 24 hours a day / 7 days a week
Technical Support (800) 847-7597 7am-7pm Mon-Fri / Sat 8-2 CT
Parts Sales (888) 393-6484 7am-7pm Mon-Sat CT
Training Center (256) 774-4051 8am-5pm Mon-Fri CT
We b Co n t a C t s :
Web Site Address Description
LG USA www.lgusa.com Product information
Customer Service us.lgservice.com User manuals, FAQs
GCSC aic.lgservice.com Service manuals, parts, bulletins
Customer Service Academy www.lgcsacademy.com Web training, discussion forum
Live Training lge.webex.com Live training
Published July 2008 by LG Electronics USA Training Center
Copyright © 2008 LG Electronics of Alabama, Inc.
IMPORTANT SAFETY NOTICE
This manual was prepared for use only by properly trained audio-visual service technicians. When servicing this product, under no circumstances
should the original design be modified or altered without permission from LG Electronics. Unauthorized modifications will not only void the
warranty, but may lead to property damage or user injury. All components should be replaced only with types identical to those in the original
circuit and their physical location, wiring, and lead dress must conform to original layout upon completion of repairs. If any fuse (or Fusible
Resistor) in this TV receiver is blown, replace it only with the factory specified fuse type and rating. When replacing a high wattage resistor
(Oxide Metal Film Resistor, over 1W), keep the resistor 10mm away from PCB. Always keep wires away from high voltage or high temperature
parts. Do not attempt to modify this product in any way.
Special components are also used to prevent shock and fire hazard and are required to maintain safe performance. No deviations are allowed
without prior approval by LG Electronics. Service work should be performed only after you are thoroughly familiar with these safety checks and
servicing guidelines. Circuit diagrams may occasionally differ from the actual circuit used. This way, implementation of the latest safety and
performance improvement changes into the set is not delayed until the new service literature is printed.
ElECTROSTATICAllY SENSITIvE 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 electricity.
Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off any electrostatic charge on the
body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging wrist strap device, which should
be removed for potential shock reasons prior to applying power to the unit under test. After removing an electrical assembly equipped with ES
devices, place the assembly on a conductive surface such as an ESD mat, to prevent electrostatic charge buildup or exposure of the assembly.
Use only a grounded-tip soldering iron to solder or unsolder ES devices. Use only an anti-static solder removal device. Some solder removal
devices not classified as “anti-static” can generate electrical charges sufficient to damage ES devices. Do not use refrigerant-propelled chemicals
which can generate electrical charge sufficient to damage ES devices. Do not remove a replacement ES device from its protective package until
immediately before you are ready to install it.
REGUlATORY INFORMATION
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits
are designed to provide reasonable protection against harmful interference when the equipment is operated in a residential installation. This
equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may
cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and
on, the user is encouraged to try to correct the interference by one or more of the following measures: Reorient or relocate the receiving antenna;
Increase the separation between the equipment and receiver; Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected; Consult the dealer or an experienced radio/TV technician for help.
The responsible party for this device’s compliance is: LG Electronics of Alabama, Inc. 201 James Record Road. Huntsville, AL 35813, USA. Digital
TV Hotline: 1-800-243-0000
Table of ConTenTs
OVERVIEW .................................................. 5
Introduction ....................................................5
Basic Troubleshooting Steps ...........................5
Caution............................................................5
Model Number Structure ...............................6
Serial Number Structure .................................6
Remote Control ..............................................7
New Features .................................................7
Computer Connection ....................................8
Service Menu ...................................................8
Power Consumption .......................................8
Service Remote ...............................................9
Check Firmware Version ............................. 10
Update Firmware ......................................... 10
42PG20 Dimensions .................................... 11
50PG20 Dimensions .................................... 11
DISASSEMBLY ........................................... 12
Introduction ................................................. 12
Back Cover Removal .................................... 12
Switch Mode Power Supply Removal .......... 13
Y-Sus board Removal .................................... 13
Y-Drive board Removal ............................... 13
Z-Sus board Removal ................................... 13
Main board Removal .................................... 13
Control Button Board Removal ................... 13
X-Drive boards Removal .............................. 13
TCP Connector Removal ............................. 15
P232 & P331 Connector Removal ............... 15
Control Button board removal .................... 16
42PG20 Exploded View ............................... 17
Block Diagram .............................................. 18
Signal and Voltage Block Diagram ................ 19
CIRCUIT DESCRIPTIONS ......................... 20
Introduction ................................................. 20
Adjustment Order **Important**................ 20
Power Supply (SMPS) ................................... 21
Y-Sus Board .................................................. 29
Y-Drive Board .............................................. 37
Z-Sus Board ................................................. 42
Control Board .............................................. 44
X-Drive Boards ............................................ 51
Left and Right X-Drive Removal .................. 55
Main (Digital) Board ..................................... 56
Power Switch and Keypad ........................... 61
DISASSEMBLY ........................................... 63
Introduction ................................................. 63
Back Cover Removal .................................... 63
Power Supply Board Removal ...................... 63
Y-Sus Board Removal ................................... 64
Top Y-Drive Board Removal ......................... 64
Bottom Y-Drive Board ................................. 64
Z-Sus Board Removal ................................... 65
Main Board Removal .................................... 65
Control Board Removal ............................... 65
X-Board Removal ......................................... 65
TCP connector removal ............................... 67
P232 & P331 connector removal ................. 67
50PG20 Exploded View ............................... 68
Block Diagram .............................................. 69
Signal and Voltage Block Diagram ................ 70
CIRCUIT DESCRIPTIONS ........................ 71
Introduction ................................................. 71
Adjustment Order **Important**................ 72
Power Supply ............................................... 72
Y-Sustain ....................................................... 82
Y-drive .......................................................... 88
Z-Sus Board ................................................. 93
Control Board .............................................. 97
X-Drive Boards .......................................... 102
Left and Right X-Drive Removal ................ 107
Main (Digital) Board ................................... 108
SCHEMATICS .......................................... 111
42PG20 :: Interconnect .............................. 111
42PG20 :: Waveforms ................................ 112
42PG20 :: Main Board :: Video & BCM ...... 113
42PG20 :: Main Board :: Control ............... 114
42PG20 :: Main Board :: DDR Memory ..... 115
42PG20 :: Main Board :: Tuner ................... 116
42PG20 :: Main Board :: Audio Processor . 117
42PG20 :: Main Board :: Power Regulator . 118
42PG20 :: Main Board :: Inputs .................. 119
42PG20 :: Main Board :: HDMI & USB ...... 120
42PG20 :: Power Supply :: PFC & MCU .... 121
42PG20 :: Power Supply :: Multi & Stby..... 122
42PG20 :: Power Supply :: VA & VA .......... 123
42PG20 :: Main Board :: PCB Layout ......... 124
42PG20 :: Main Board :: Bottom PCB ....... 125
42PG20 :: Sub Boards :: PCB Layout ......... 126
50PG20 :: Main Board :: Interconnect ....... 127
50PG20 :: Main Board :: Control ............... 128
50PG20 :: Main Board :: Video & BCM ...... 129
50PG20 :: Main Board :: Control ............... 130
50PG20 :: Main Board :: DDR Memory ..... 131
50PG20 :: Main Board :: Tuner ................... 132
50PG20 :: Main Board :: Audio Processor . 133
50PG20 :: Main Board :: Power Regulator . 134
50PG20 :: Main Board :: Interface .............. 135
50PG20 :: Main Board :: HDMI & USB ...... 136
50PG20 :: Main Board :: PCB Layout ......... 137
50PG20 :: Main Board :: Bottom PCB ....... 138
50PG20 :: Sub Boards :: PCB Layout ......... 139
PDP Training - Fall 2008 3
OVERVIEW
OVERVIEW 2008 PDP
INTRODUCTION
This manual covers two models from the 2008 Plasma Display Panel (PDP) product line.
Each model is an HDTV with integrated HD tuner. All 2008 PDP models include USB Media
Host and SimpLink. USB Media Host consists of a USB port on the back of the TV that
supports USB flash memory drives loaded with media or firmware for the TV. SimpLink
allows for control of other LG SimpLink products via the HDMI connection.
All PDP TV models are covered by a one year parts and labor warranty. Refer to the last
page of the owner’s manual for more warranty information. When making a warranty repair
involving a service bulletin, be sure to refer to the service bulletin number in the warratny
claim.
BASIC TROUBLESHOOTING STEPS
Define - Look at the symptom carefully and determine what circuits could be causing the
failure. Use your senses Sight, Smell, Touch and Hearing. Look for burned parts and
check for possible overheated components. Capacitors will sometimes leak dielectric
material and give off a distinct odor. The frequency of power supplies will change with
the load, or listen for a relay closing, etc. Observation of the front Power LED may
give some clues.
Localize - Carefully check the symptom and determining the circuits to be checked. After
giving a thorough examination using your senses, check the DC Supply Voltages to
those circuits under test. Always confirm the supplies are not only the proper level,
but are noise free. If the supplies are missing check the resistance for possible short
circuits.
Isolate - To further isolate the failure, check for the proper waveforms with an Oscilloscope
to make a final determination of the failure. Look for correct Amplitude Phasing and
Timing of the signals. Also check for the proper Duty Cycle of the signals. Sometimes
“glitches” or “road bumps” will be an indication of an imminent failure.
Correct - The final step is to correct the problem. Be careful of static sensitive components
and make sure to check the DC Supplies for proper levels. Make all necessary
adjustments. Lastly, always perform a Safety AC Leakage Test before returning the
product back to the Customer.
CAUTION
1) A (approximately) 10 minute pre-run time is required before any adjustments are
performed.
PDP Training - Fall 2008 5
OVERVIEW
403 MX XQ
0 5 1 0 6
Sequential Number (5-7 Numbers)
Production Info (2 Letters)
Production Site (2 Letters)
Production Year and Month (3 Numbers). Ex, March 2004.
2) Refer to the Voltage Sticker inside the panel when making adjustments on the Power
Supply, Y-Sus and Z-Sus boards and adjust to the specified voltage level (±1/2 V).
3) The PDP module uses high voltage, be cautious of electric shock from the PDP
module. Before circuit board removal, check that the Power Supply and drive circuits
are completely discharged because of residual current stored.
4) C-MOS circuits are used extensively for processing the Drive Signals and should be
protected from static electricity.
5) The Plasma television and/or PDP Module must be carried/transported vertical, not
horizontal. (If laying down on its face, foam padding is a must).
6) Exercise care when making voltage and waveform checks to prevent costly short circuits
from damaging the unit.
7) Be cautious of loose screws and other metal objects to prevent a possible short in the
circuitry.
8) New panels and frames are much thinner than previous models. Be Careful with flexing
these panels. Be careful with lifting panels from a horizontal position. Damage to the
Frame mounts or panel can occur.
MODEL NUMBER STRUCTURE
42 P G 2 0 - U A
Screen Size
Display Type
Brand
Z= Zenith
Blank = LG
SERIAL NUMBER STRUCTURE
P = Plasma
L = LCD
D = DLP RPTV
J = Projector
Year
G = 2008
Region
U = North America
B = Europe & NA
Chassis Version
Series/Feature Level
20/25 = 720p HDTV
30 = Full HD
60 = Full HD & THX
6 PDP Training - Fall 2008
INPUT
FAV
MUTE
TV
STB
POWER
Q. MENU MENU
AV MODERETURN
ENTER
VOL
CH
1 2 3
4 5 6
7 8
0
9
FLASHBK
P
A
G
E
DVD
VCR
REMOTE CONTROL
2008 models feature a newly designed, easier to use remote. The remote
has fewer buttons than previous designs which was accomplished by
moving many functions to an on-screen Quick Menu. The “Q. MENU”
button on the remote opens the Quick Menu and the user can choose
between options like aspect ratio, closed captions, sleep timer, etc.
The remotes are programmable for other devices. They also support
SimpLink devices. When using SimpLink, the device buttons on the
remote do not need to be pressed to switch modes before controlling
external equipment. So, the External devices are controlled by the TV
instead of the remote.
NEW FEATURES
Below are some of the new features on some 2008 PDP TVs.
FluidMotion (180Hz Effect) - Enjoy smoother, clearer motion with all
types of programming such as sports and action movies. The moving
picture resolution give the impression of performance of up to 3x
the panels actual refresh rate.
OVERVIEW
Full HD 1080p Resolution - Displays HDTV programs in full 1920 x
1080p resolution for a more detailed picture. Standard HD PDPs
are 1365 x 768p.
Expert Menu - Expert Menu features Imaging Science Foundation
Certified Calibration Controls (ISFccc) which allow precise in-home
picture calibrations.
Public Display Mode - This is an additional menu with advanced startup
options like startup volume, start channel, etc. This can be accessed
by holding the Menu key until it vanishes. Then key in 1, 1, 0, 5,
and press enter.
PDP Training - Fall 2008 7
SERVICE REMOTE
NUM KEY FUNCTION
1 POWER To turn the TV on or off
2 POWER ON To turn the TV on automatically if the power is supplied to the TV. Use the POWER key to deactivate; It
3 MUTE To activate the mute function.
4 P-CHECK To check TV screen image easily.
5 S-CHECK To check TV screen sound easily
6 ARC To select size of the main screen (Normal, Spectacle, Wide or Zoom)
7 CAPTION Switch to closed caption broadcasting
8 TXT To toggle on/off the teletext mode
9 TV/AV To select an external input for the TV screen
10 TURBO SOUND To start turbo sound
11 TURBO PICTURE To start turbo picture
12 IN-START To enter adjustment mode when manufacturing the TV sets.
13 ADJ To enter into the adjustment mode. To adjust horizontal line and sub-brightness.
14 MPX To select the multiple sound mode (Mono, Stereo or Foreign language).
15 EXIT To release the adjustment mode.
16 APC(PSM) To easily adjust the screen according to surrounding brightness.
17 ASC(SSM) To easily adjust sound according to the program type.
18 MULTIMIDIA To check component input.
19 FRONT-AV To check the front AV.
20 CH To move channel up/down or to select a function displayed on the screen.
21 VOL To adjust the volume or accurately control a specic function.
22 ENTER To set a specic function or complete setting.
23 PIP CH-(OP1) To move the channel down in the PIP screen. To use as a red key in the teletext mode.
24 PIP CH+(OP2) To move the channel in the PIP screen. To use as a green key in the teletext mode.
25 PIP SWAP(OP3) To switch between the main and sub screens. To use as a yellow key in the teletext mode.
26 PIP INPUT(OP4) To select the input status in the PIP screen. To use as a blue key in the teletext mode.
27 EYE To set a function that will automatically adjust screen status to match. The surrounding brightness so natural
28 MENU To select the functions such as video, voice, function or channel.
29 IN-STOP To set the delivery condition status after manufacturing the TV set.
30 STILL To halt the main screen in the normal mode, or the sub screen at the PIP screen. Used as a hold key in the
31 TIME Displays the teletext time in the normal mode. Enables to select the sub code in the teletext mode.
32 SIZE Used as the size key in the PIP screen in the normal mode. Used as the size key in the teletext mode.
33 MULTI PIP Used as the index key in the teletext mode. Top index will be displayed if it is the top text.
34 POSITION To select the position of the PIP screen in the normal mode. Used as the update key in the teletext mode
35 MODE Used as Mode in the teletext mode.
36 PIP To select the simultaneous screen.
37 TILT To adjust screen tilt.
38 0~9 To manually select the channel.
OVERVIEW
should be deactivated when delivered.
To adjust the screen voltage (automatic): In-start mute Adjust AV (Enter into W/B adjustment mode).
W/B adjustment (automatic): After adjusting the screen W/B adjustment Exit two times
color can be displayed.
teletext mode. Page updating is stopped.
(Text will be displayed if the current page is updated.)
PDP Training - Fall 2008 9
OVERVIEW
LP81A LPL L42FHD
Main V1.62 USB V2.14
00 HDCP 0
UTT 97
Tool Option1 39848
Tool Option2 51
Area Option 1
OPTION1 43
OPTION2 46
OPTION3 0
OPTION4 0
System Control
Audio Prescale
Threshold
Power Off History
Panel Control
Davinci / Auto Test
LP81A LPL L42FHD
Main V1.62 USB V2.14
00 HDCP 0
UTT 97
Tool Option1 39848
Tool Option2 51
Area Option 1
OPTION1 43
OPTION2 46
OPTION3 0
OPTION4 0
System Control
Audio Prescale
Threshold
Power Off History
Panel Control
Davinci / Auto Test
CHECK FIRMWARE VERSION
You can check the firmware version by
opening the service menu. It is located
near the top of the menu.
UPDATE FIRMWARE
1) Copy the firmware to the top
level on a USB flash drive and to
a folder named LG_DTV. Some
models require the LG_DTV
folder, and some don’t. Put it in
both locations if you are not sure
which is correct. Only copy the
file (or files) for the model you are
currently updating.
2) Turn on the TV and insert the USB
drive to the USB IN port.
3) If the firmware is newer than what is already installed, the upgrade menu should open
automatically. If the update menu doesn’t open, press MENU on the remote and select
OPTION. Now press the 7 key 7 times and the upgrade menu will open.
4) Select START and press ENTER on the remote to start the software upgrade.
5) The TV will copy the update from the drive and then install it. Do not turn the TV off
until it is finished.
6) The TV will automatically turn off and back on after the upgrade is successfully
finished.
7) Check the firmware version to verify the update was succesful.
10 PDP Training - Fall 2008
15.8"
400mm
26.7"
678.2mm
6.2"
158mm
40.9"
1038.9mm
28.8"
731.5mm
28.8"
731.5mm
3.4"
86.4mm
12.1"
307.3mm
Center
15.8"
400mm
6.6"
168.78mm
1.93"
49mm
Remove 4 screws to
remove stand for
wall mount
Model No.
Serial No.
Label
15.55"
394.95mm
12.4"
315mm
4.72"
120mm
17.48"
443.95mm
42PG20 DIMENSIONS
DISASSEMBLY
4
2
P
G
2
0
PDP Training - Fall 2008 11
OVERVIEW
COMPUTER CONNECTION
A computer can be connected to the RGB (VGA)
or HDMI connection on the TV. The HDMI
connection will require a DVI to HDMI adapter
if the PC has a DVI connector.
Set the monitor output resolution and vertical
frequency on the PC before connecting it to
the TV. Refer to the owner’s manual for a full
list of suported resolutions, some examples are
listed below. The message “OUT OF RANGE”
will appear on the screen if the resoultion is not
supported.
Resolution Vertical
30/40/50/60/70 series
1280x768 60Hz
1360x768 60Hz
1366x768 60Hz
50/60/70 series only
1600x1200 60Hz
1920x1080 60Hz
SERVICE MENU
The service menus can be used to make
adjustments, change color alignment, and get
software versions. There are two service menus.
The Adjust and Instart menu can be accessed
using the service remote (Service remotes are
available from LG parts). They can also be
accesed by holding down the menu button on
the TV and the remote until the user menu
disappears. The menus alternate between Adjust
and Instart every time the menu button is held
down. If the TV asks for a password, enter 0000
(four zeros).
POWER CONSUMPTION
Model
19LS4D-UA 42W 0.85 1W
20LS7D-NB 56W 0.85 1W
20LS7D-UK 56W 0.85 1W
22LC2D-UB 46W 0.85 1W
22LS4D-UA 46W 0.85 1W
23LS7D-NB 78W 0.85 1W
23LS7D-UK 78W 0.85 1W
26LC7DC-UB 110 160W 0.7 1W
26LC7DC-UK 30 160W 0.7 1W
26LC7D-UK 30 160W 0.7 1W
26LG30DC-UA 99 115W 0.36 0.8W
32LC4D-UA 150 190W 0.7 1W
32LC50C-UA 190W 3W
32LC5DC-UA 190W 3W
32LC7DC-UK 170 190W 0.7 1W
32LC7D-UB 150 190W 0.7 1W
32LC7D-UK 170 190W 0.7 1W
32LG30DC-UA 149 171W 0.36 0.8W
32LX50C-UA 190W 3W
32LX5DC-UA 190W 3W
37LC50C-UA 210W 3W
37LC5DC-UA 210W 3W
37LC7DC-UK 190 220W 0.8 1W
37LC7D-UB 180 220W 0.8 1W
37LC7D-UK 190 220W 0.8 1W
37LG30DC-UA 167 191W 0.36 0.8W
42LB50C-UA 240W 3W
42LB5DC-UA 240W 3W
42LC4D-UA 230 240W 0.8 1W
42LC50C-UA 240W 3W
42LC5DC-UA 240W 3W
42LC7DC-UK 220 240W 0.8 1W
42LC7D-UB 230 240W 0.8 1W
42LC7D-UK 220 240W 0.8 1W
42LG30DC-UA 226 244W 0.36 0.8W
TYP MAX UNIT TYP MAX UNIT
8 PDP Training - Fall 2008
DISASSEMBLY
Y-sus & Z-Sus Drive
Control (Logic)
Y-Drive
Voltage Label
Main (Digital)
Panel ID
Power Supply
Z-Sus
Right X-Board
Left X-Board
Side Input
DISASSEMBLY 42PG20
INTRODUCTION
4
2
P
G
2
0
This section of the manual will discuss disassembly of the 42PG20 PDP Direct View
Television. Upon completion of this section the Technician will have a better understanding
of the disassembly procedures, the layout of the printed circuit boards, and be able to
identify each board. The plugs listed are from left to right Pin 1,2, 3, etc. Remember to
be cautious of ESD as many semiconductors are CMOS and prone to static failure.
BACK COVER REMOVAL
Remove the 22 screws shown. Pay attention to the size and type of screw as there are
different types. Putting in the improper screw when reassembling may cause damage. The
stand does not need to be removed when removing the back.
BOARD LAYOUT
12 PDP Training - Fall 2008
DISASSEMBLY
SWITCH MODE POWER SUPPLY REMOVAL
Disconnect the following connectors: P812, P813, CN101. Remove the 8 screws holding the
board in place. Remove the board. When replacing, be sure to readjust the Va/Vs voltages
in accordance with the Panel Label. Confirm VSC, -Vy and Zbias as well.
Y-SUS BOARD REMOVAL
4
Disconnect the following connectors: P201, P801, P101, P202. Remove the 8 screws
holding the board in place. Remove the board. When replacing, be sure to readjust the
Va/Vs voltages in accordance with the Panel Label. Confirm VSC, -Vy and Zbias as well.
Y-DRIVE BOARD REMOVAL
Disconnect the following Flexible Ribbon Connectors: P1, P2, P3, P4, P5, P6, P7 and
P8. Disconnect the following connectors: P201, P801, P101, P202. Remove the 3 screws
holding the board in place. Remove the board by lifting slightly and sliding the board to
the left unseating P204 and P200. from the Y-Sus board.
Z-SUS BOARD REMOVAL
Remove the support frame holding the Main board. Disconnect the following connectors:
P1, P2 and P3. Remove the 3 screws holding the board in place. Remove the board. When
replacing, be sure to readjust the Va/Vs voltages in accordance with the Panel Label.
Confirm VSC, -Vy and Zbias as well.
MAIN BOARD REMOVAL
Disconnect the following connectors: P701, P302, P303 and JK501. Remove the 2 screws
holding on the decorative plastic piece on the right side. Remove the 4 screws holding
the board in place. Remove the board.
2
P
G
2
0
CONTROL BUTTON BOARD REMOVAL
Disconnect the following connectors: P121, P160, P161 and P162. Remove the 2 screws
holding the board in place. Remove the board. (Note: Power board is behind the Control
board. Remove it’s 2 screws and remove.
X-DRIVE BOARDS REMOVAL
X-Board Removal will require the most disassembly of all the boards. All the Brackets
and Assemblies marked A-F (Image on next page) will need to be removed including the
Stand. Before an X-Board can be removed. The Heat Sink assembly will also need to be
removed.
Lay the Plasma down carefully on a padded surface. Make sure AC is removed and remove
the back cover and the stand. Carefully remove the LVDS Cable P121 from the Control
board by pressing the Locking Tabs together and pull the connector straight back to
remove the cable. (This prevents damage).
PDP Training - Fall 2008 13
DISASSEMBLY
Y-sus & Z-Sus Drive
Control (Logic)
Y-Drive
Main (Digital)
Power Supply
Z-Sus
Right X-Board
Left X-Board
A
F
B
E
E
C
D
A
Locking Tabs
Press In
Press In
Left X-Board
Right X-Board
A) Remove the sStand
mounting support
plastic piece.
4
2
P
G
2
0
B) Remove the stand
m et a l s up p o r t
bracket, unplug AC
ground lug.
C) Remove the 2 screws
from the decorative
black plastic piece
around side input
jacks (Marked B)
and remove.
D) R em ov e t h e 2
screws at the top
of the Main board
Mounting Bracket and peel the tape from the
bottom. Remove connectors P303 and JK501.
Carefully reposition the main board and mounting
bracket up and off to the right side.
E) Remove the metal support brackets marked “E”.
F) Remove the 13 screws holding the heat sink and
carefully lift it straight up and off (remember that
the TCP IC’s are located under the heat sink).
Disconnect all TCP ribbon cables from the defective
X-Drive board and remove the 5 screws holding
the board in place. Reassemble in the reverse order.
Recheck Va/Vs/V-Scan/-VY/Z-Drive.
14 PDP Training - Fall 2008
DISASSEMBLY
TCP CONNECTOR REMOVAL
Lift up the lock as shown by arrows. (The Lock can be easily broken. It needs to be handled
carefully.) Pull TCP apart as shown by the arrows. The TCP Film can be easily damaged,
handle with care.
P232 & P331 CONNECTOR REMOVAL
The X-Drive boards can be removed after removing the back cover, the main board, and
the heat sink covering the TCPs is removed (15 screws).
Peel the tape off
the connectors and
gently pry the locking
mechanism upward.
4
2
P
G
2
0
Gently pry the locking mechanism upward on all TCP
connectors P201-206 or P301-306.
Carefully lift the TCP ribbon up and off the cushion and
out of the way.
PDP Training - Fall 2008 15
4
2
P
G
2
DISASSEMBLY
CONTROL BUTTON BOARD REMOVAL
The control button board and power switch board are located in the lower left hand section
(as viewed from the rear).
To remove, unplug the connector P101 and remove the 2 screws. Under each screw there
is a black tab. Release these tabs to lift the board upward. Then remove the connector
from the power switch board and remove it’s two screws.
0
16 PDP Training - Fall 2008
300
305
400
203
205
202
240
204
302
200
206
250
201
303
304
306
900
580
560
571
120
561
570
301
260
590
501
270
603
520
602
601
42PG20 EXPLODED VIEW
DISASSEMBLY
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Part numbers subject to change.
Check GCSC (aic.lgservice.com) for
the current part numbers.
Location Part Num Description Location Part Num Description
120 EAB42609901
200 EAJ41970710
201 EBR39594901
202 EBR39712601
203 EBR39595001
204 EBR39595101
205 EBR39706801
206 EBR41668901
240 AJJ35680107
250 AJJ35680108
260 AJJ35680203
270 AJJ35680204
300 ABJ35121812 Front Cabinet 601 ABA35619217
301 ABA36825001 Speaker Bracket Assembly 602 MGJ41163807
302 AJJ35122402
303 AJJ35122502
Full Range Speaker
PDP Panel (PDP Module)
Control board (CTRL)
Y-drive (YDRV)
Left X-Drive (XRLB)
Right X-Drive (XRRB)
Y-Sustain (YSUS)
Z-Sustain (ZSUS)
Top Right Support
Top Left Support
Bottom Right Support
Bottom Left Support
Top Filter Support
Bottom Filter Support
304 AJJ35122602
305 MDJ42350902
306 AJJ35122702 Left Supporter Assembly
400 ACQ35123228 Rear Cover Assembly
501 MGJ41164512 Main Supporter Plate
520 EBR43929102 Hand Insert PCB Assembly,Main
560 EBR43385504
560 EBR48957101
561 MBG41119902
570 EBR44168002
571 ABA36967703 Bracket Assembly
580 EAY43533901
603 MGJ40268206 Side AV Shield
900 AAN35132205
Right Filter Support
Glass Filter
Main/Digital PCB
Sub PCB
Control Buttons
Sub PCB
Power Supply (SMPS)
Side Input Bracket Assembly
Main board Supporter
Stand (Base Assembly)
0
PDP Training - Fall 2008 17
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CIRCUIT DESCRIPTIONS
BLOCK DIAGRAM
0
18 PDP Training - Fall 2008
SIGNAL AND VOLTAGE BLOCK DIAGRAM
42PG20 SIGNAL and VOLTAGE DISTRIBUTION DIAGRAM
Display Panel
Horizontal Address
P100
5V
Drive Signal
NEW
Y-SUS
PWB
With Z-Drive
P204
P201
P801
P211
P101
P202
Drive Data
Clock (i2c)
P200
M5V, Va, Vs
P812
P813
CN101
STB +5V, 16V, 5V
SMPS
Turn On
Commands
SMPS
PWB
AC
Input
Filter
NEW
P1
SMPS OUTPUT VOLTAGES
STB +5V, 16V, 5V
Z-SUS
Drive Signals
Logic Signals
P160
AC Voltage
Det
P701
P302
P303
JK501
MAIN
PWB
Speakers
Control
Keys
Power
Keys
X-PWB-Right
X-PWB-Left
P201 P202 P203 P204 P205 P206 P301 P302 P303 P304 P305 P306
RGB Logic Signals
15V, Va
RGB Logic Signals
3.3V
CONTROL
PWB
P162
LVDS
Y Drive PWB
Z SUS PWB
P161
P121
P1 P2 P3 P4 P5 P6 P7 P8
P2P3
Outputs Only
P232
P211 P311 P331
Display Panel Vertical Address
IR
Vs
Display Panel
Horizontal Address
5V
DISASSEMBLY
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PDP Training - Fall 2008 19
CIRCUIT DESCRIPTIONS
Remember, the Voltage Label MUST be followed,
it is specific to the panel’s needs.
All label references are from a specific panel.
They are not the same for every panel encountered.
-VY
Z_BIAS
Panel
“Rear View”
Manufacturer
Bar Code
Set-
Up
Ve
Vscan
CIRCUIT DESCRIPTIONS 42PG20
INTRODUCTION
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It is critical that the DC Voltage adjustments be checked whenever troubleshooting a
problem. Especially when:
1) The SMPS (Switch Mode Power Supply), Y-Sus (Y-Sustain) or Z-Sus (Z-Sustain)
are replaced.
2) The panel is replaced, since the SMPS does not come with new panel.
3) A picture issue is encountered.
PANEl lAbEl
(1) Model Name
(2) Bar Code
(3) Manufacture No.
(9) TUV Approval Mark
(10) UL Approval Mark
(11) UL Approval No.
(4) Adjusting Voltage DC, Va, Vs
(5) Adjusting Voltage (Set Up/-Vy/Vsc/Ve/Vzb)
(6) Trade name of LG Electronics
(7) Manufactured date (Year/Month)
(8) Warning
ADJUSTMENT ORDER **IMPORTANT**
DC vOlTAGE ADJUSTMENTS
SMPS board: Va Vs (Do SMPS adjustments first)•
Y-Sus board: Adjust Vscan, -Vy•
Y-Sus board: Adjust Zbias •
WAvEFORM ADJUSTMENTS
Y-Sus board: Ramp Up, Ramp Down.
Only necessary when:
1) The Y-Sus board is replaced.
2) “Mal-Discharge” problems.
3) Abnormal picture issues.
20 PDP Training - Fall 2008
(12) Model Name
(13) Max. Watt (Full White)
(14) Max. Volts
(15) Max. Amps
POWER SUPPLY (SMPS)
Hot Ground Symbol represents a SHOCK Hazard
F801
340V Fuse
10Amp/230V
F101
340V Fuse
10Amp/230V
P812
To Y/Z-Sus
Standby
Source
PFC
Circuit
CN 101
AC Input
VS Source
VA Source
IC701
Sub Micon
P813
To Main
VA VR901
380V Source
16V, 12V, 5V, 3.2V
Source
VS VR951
CIRCUIT DESCRIPTIONS
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= Shock Hazard
PDP Training - Fall 2008 21
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CIRCUIT DESCRIPTIONS
SMPS Outputs
Board Voltage Description
VS Drives the display panel Horizontal Grid
Y-Sus
Main
VA Responsible for display panel Vertical Grid
M5V VCC
16V Audio B+ Supply
5V Control Circuits
Used to develop Bias Voltages on the Y-Sus,
X-Drive, and Control boards
Adjustments
Voltage Location
VA RV901
VS RV951
M5V VCC Fixed
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POWER SUPPlY OPERATION
Refer to the figures on page 25-27. AC Voltage is supplied to the SMPS board at Connector
CN101 from the AC Input Filter. Standby 5V is developed from 340V source supply
(which during standby measures 159V hot ground). This supply is also used to generate
all other voltages on the SMPS.
The 5V (standby) voltage is routed to the Sub Micon circuit (IC701) on the SMPS and
through P813 to the Main board or Micon (IC100). LD703 will glow green to indicate
STBY 5V has arrived.
AC detect Pin 18 of P813 is generated on the SMPS by monitoring the AC input and
rectifying a small sample voltage. This AC Detect Voltage is routed to IC701 on the Sub
Micon on the SMPS and the Micon (IC100) located on the Main board. It is used as a
basic “SMPS OK” signal.
When the Micon (IC100) on the Main board receives an “ON“ command from either the
keyboard or the Remote IR Signal, it outputs a high to RL-ON. This signal first turns on
a DC level shifter Q706 which creates 5V General. LD703 now glows amber indicating
5V General has been generated. This 5V General now provides the pull up voltages that
supply the output circuits to the SMPS. The RL-ON enters the SMPS board at Pin 19 of
P813. The RL-ON Voltage is sensed by the Sub Micon (IC701) circuit which causes the
Relay Drive Circuit to close Relay RL101. this brings the PFC source up to full power by
increasing the 159V standby to 340V. At this time the 16V source becomes active and
sent to the Main board via P813.
The next step is for the Micon (IC105) on the Main board to output a high on M5V_ON
Line to the SMPS at P813 Pin 21 which is sensed by the Sub Micon IC (IC701) on the
SMPS turning on the 5V VCC line. The last step to bring the supply to “Full Power” occurs
when the Micon (IC100) on the Main board brings the VS-ON line high at Pin 20 of
P813 on the SMPS board which when sensed by the Sub Micon IC (IC701) turns on the
VA and VS Supplies (VA is brought high before VS).
Note: If a voltage is missing, check for proper resistance before proceeding.
22 PDP Training - Fall 2008
CIRCUIT DESCRIPTIONS
Understanding the Power On Sequence when Troubleshooting a possible Power Supply
Failure will simplify the process of isolating which circuit board failed to operate properly.
In this Section we will investigate the Power on Sequence and examine ways to locate
quickly where the failure occurred.
Check the Power On LED for Operation. A Red LED indicates a presence of 5V STB and
AC-ON/DETECT. Failure of the Power ON LED to light is an indication of loss of 5V STB
or AC ON/ Detect remember the 5V STB and AC-ON/DETECT are developed on the
SMPS and sent to the Main board. Check LD703 for Green glow.
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When Power is pressed, look for LD703 to change to Amber. Listen for a Relay Click. The
click of the Relay is an indication of RL-ON going high. RL-ON is sent from the Main board
to the SMPS and when present, the IC701 controls the relay operation. RL-ON going High
and no relay is a failure of the SMPS. RL-ON staying low is a failure of the Main board.
Relay Operation means that the SMPS if working properly will output the 16V Supply to
the Main board. This voltage will allow the Tuner, Audio and Video Circuits on the Main
board to function, and if connected to an Antenna Input, Audio would be present. If the
Relays closed and these supplies failed suspect a problem with the SMPS.
The next step of operation calls for the M5V_ON line from the Main board to the SMPS
to go high pin 21 of P813. A high on the M5V_ON line activates the 5V VCC line. Loss
of 5V VCC results in no “Raster”, no Display Panel Reset, no Y, Z, Control or X-board
operation. Loss of 5V VCC and M5V_ON going high could be caused by any of these
boards or failure of the SMPS. M5V_ON staying low indicates a problem on the Main
board.
VS-ON is the last step of the Power Sequence and is responsible for bringing the VS
and VA voltages up. The VS-ON signal pin 20 of P813 is sent from the Main board to
the SMPS as a high, VS and VA and full operation of the Display Panel are now enabled.
Loss of VS-ON results in loss of VA and VS and no Raster, no Panel Display Reset but
audio would be present. If VS-ON went high and VS and VA where missing the problem
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PDP Training - Fall 2008 23
CIRCUIT DESCRIPTIONS
Model : PDP42G1####
||||||||||||||||||||||||||||||||||||||||||||||||||||
801K542G1008000 .AKAZBED
Voltage Setting :DC 5V Va :65V/ Vs:195V
NA / -190 / 140 / NA / 100
Vs TP
P812
Pin 1 or 2
Use Full White Raster
Va TP
P812
Pin 5 or 6
2
4
6
8
10
12
14
16
18
22
16V
Gnd
NC
Gnd
5VSTB
5VSTB
Gnd
Gnd
AC Det
VS_ON
Auto Gnd
2
4
6
8
10
12
14
16
18
22
16V
Gnd
NC
Gnd
5VSTB
5VSTB
Gnd
Gnd
AC Det
VS_ON
Auto Gnd
20
3
5
7
9
11
13
15
17
19
21
Gnd
NC
Gnd
5VSTB
5VSTB
Gnd
Gnd
5_V Det
RL_ON
M5V_ON
1
15V
3
5
7
9
11
13
15
17
19
21
Gnd
NC
Gnd
5VSTB
5VSTB
Gnd
Gnd
5_V Det
RL_ON
M5V_ON
1
15V
could be caused by a failure on the SMPS or a circuit
using these voltages. A resistance check should narrow
the possible failures quickly.
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POWER SUPPlY STATIC TEST
This test can confirm the proper operation of the SMPS
without the need to exchange the board.This Power
Supply can operate in a No Load State. This means that
by applying AC power to SC101 and all other plugs
disconnected, this power supply will function. Simply
removing P813 (Lower Right Hand Side of the board),
will cause the “AUTO” Pin 22 to go high from its normal
low state allowing the Power Supply to go to full power
on mode when AC Power is Supplied. Be careful after this
test and make sure the VA and VS lines have discharged before reconnecting the supply
cables.
If the Y-Sus and Z-Sus boards are working normal, “Display Panel Reset” will be visible
when the SMPS comes up to full power. Shorting the Auto Pattern Gen. test points at
this time should result in test patterns on the screen.
vS/vA ADJUSTMENTS
This Power Supply will come up and run with “no” load (P812 pulled). Pull P813, apply AC
power, and the Power Supply starts. Y-Sus/Z-Sus runs “Yes” both Y and Z waveforms.
24 PDP Training - Fall 2008
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