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Panasonic Services Company
National Training

TH-42PX20U/TH-50PX20U
TH-42PA20U/TH-37PA20U
Plasma Display Panel

GP6D Chassis
Update Information

Warning
This service information is designed for experienced repair technicians only and is not designed for use by the general public. It does
not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product. Products
powered by electricity should be serviced or repaired only by experienced professional technicians. Any attempt to service or repair
the product or products dealt with in this service information by anyone else could result in serious injury or death.

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2
Table of contents

Objective..............................................................................................................5
Model Line Up .....................................................................................................7
Performance Comparison ..................................................................................8
SD Models.........................................................................................................8
HD Models ........................................................................................................8
Specifications......................................................................................................9
SD Models.........................................................................................................9
HD Models ........................................................................................................9
New Features and Circuit Improvements .......................................................10
42" SD PCB Board Layout Diagram ................................................................11
Board Comparison Chart .................................................................................12
Video Signal Block Diagram ............................................................................13
Video Signal Path Explanation ........................................................................15
NTSC \ 480i Video Signal Path .......................................................................15
DVI Input .........................................................................................................17
DVI RGB to YUV Conversion ..........................................................................18
Digital Processor .............................................................................................19
Main Picture ....................................................................................................19
RGB Amplifier..................................................................................................21
RGB/PC Select................................................................................................22
D Board Outline...............................................................................................23
Sync Signal Process .......................................................................................24
SC Board Explanation ......................................................................................25
SS Board Explanation ......................................................................................28
Power Supplies (GP6D Chassis) .....................................................................31
Standby power supply .....................................................................................31
VSUS High Voltage Source.............................................................................32
Main Power Supply .........................................................................................34
VDA and other Voltage Sources......................................................................35
Protection Circuits............................................................................................37
System Control Circuit .....................................................................................39
Panel Operations.............................................................................................39
TV Operations .................................................................................................40
Diagnostic Procedures.....................................................................................41
Diagnostic Flow Charts ....................................................................................42
No Power ........................................................................................................42
No Picture Flowchart 1 ....................................................................................43
No picture Flowchart 2 ....................................................................................44
Dark picture Flowchart ....................................................................................45
Local screen failure ..........................................................................................46
Service Hints ...................................................................................................47
Adjustments ......................................................................................................52

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+B Set-up ........................................................................................................52
Confirmation ....................................................................................................52
Driver Set-up ...................................................................................................53
Panel Label information...................................................................................53
Initialization Pulse Adjust.................................................................................54
P.C.B. (Printed Circuit Board) exchange procedure ........................................55
Adjustment Volume Locations .........................................................................55
Test Point locations .........................................................................................56
Serviceman mode (Electronic Controls).........................................................56
Serviceman mode (Electronic Controls).........................................................57
CAT (computer aided test) Mode ....................................................................58
I2C Mode .........................................................................................................59
I2C Menu Structure..........................................................................................60
CD mode .........................................................................................................61
SD Mode .........................................................................................................62
Alignment Procedures......................................................................................63
Pedestal Setting ..............................................................................................63
NTSC White Balance Adjustment....................................................................64
HD Panel White Balance Adjustment ..............................................................65
Sub Brightness Setting....................................................................................66
Hotel Mode Operation .....................................................................................67
Service Contact Information ............................................................................70

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Objective
The information provided in this document is designed to assist the technician in
determining the defective printed circuit board. The troubleshooting flow charts,
signal path charts and connector information should provide enough detail to the
technician for the accurate repair of the product. Alignment and adjustment
procedures are also included in this document.
The Block diagrams and the schematic drawings reference the model TH-
42PHD5, TH-42PX20U and TH-42PA20U but the technology is consistent with
any GPH5D and GP6D series Plasma display panels.

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Model Line Up

TH-50PX20U TH-42PX20U
50-inch (127 cm) HD Version 42-inch (106cm) HD Version
2 Component Video Inputs 2 Component Video Inputs
3 Composite Video Inputs 3 Composite Video Inputs
3 S-Video Inputs 3 S-Video Inputs
1 HDMI input 1 HDMI input
Scalable PIP (1/4 to 1/16) Scalable PIP (1/4 to 1/16)
PC / SD Card Inputs PC / SD Card Inputs
Integrated Speaker System Integrated Speaker System
BBE sound BBE sound
1080i / 480p capable 1080i / 480p capable
720p (PC input only) 720p (PC input only)

TH-42PA20U TH-37PA20U
42-inch (106 cm) SD Version 37-inch (94cm) SD Version
2 Component Video Inputs 2 Component Video Inputs
3 Composite Video Inputs 3 Composite Video Inputs
3 S-Video Inputs 3 S-Video Inputs
1 DVI input 1 DVI input
Scalable PIP (1/4 to 1/16) Scalable PIP (1/4 to 1/16)
Integrated Speaker System Integrated Speaker System
BBE sound BBE sound
1080i / 480p capable 1080i / 480p capable

7
Performance Comparison
SD Models
Chassis GP5D GP6DU
Panel Size 42 37 42
Pixels (H x V) 852 x 480p 852 x 480p 852 x 480p

Brightness Peak 370 370 370
(Set) (cd/m2)
Contrast Dark 3000:1 4000:1
150 lux 140:1 120:1 160:1
Gradation 1024 shades 1536 shades
Sharpness Good Vivid
Color Temp. 11000 11000
Power Consumption
Maximum 295W 225W 265W
Standby Normal 2.8W 2.8W 1.5W
Standby Save On 0.6W
Power Off 1.5W 1.5W 0.4W

HD Models
Chassis GPH5D GPH6D
Panel Size 50 42 50 42
Pixels (H x V) 1366 x 1024 x 1366 x 768p 1024 x 768p
768p 768p

Brightness Peak 260 250 300 360
(Set) (cd/m2)
Contrast Dark 3000:1 4000:1
150 lux 90:1 160:1
Gradation 1024 shades 1536 shades
Sharpness Good Vivid
Color Temp. 11000 11000
Power Consumption
Maximum 495W 225W 445W 265W
Standby Normal 3.0W 3.0W 1.5W 1.5W
Standby Save On 0.6W 0.6W
Power Off 1.7W 1.7W 0.4W 0.4W

8
Specifications
SD Models
Model Number TH-42PA20U/P
Chassis GP6DU
Panel Screen Size SD type 42" 16 x 9 (920 x 518 mm)
Number of H 852 x 480 (VGA)
Pixels
Number of Dots H 2556 x V 480
Pixel Size W 1.08 x H 1.08 mm
Drive Method AC Type Sub Field Drive System, Variable sub Field
Power Source AC 120V 50 /60 Hz
Power Consumption 425W Standby (0.8W)
Applicable Signals NTSC
525i (480i), 525p (480p), 625i (575i), 625p (575p),
750p (720p), 1125 (1080)/60i, 50i, 24p, 24sf
VGA, SVGA, XGA, SXGA, UXGA
Contrast 4000:1
Dimensions (W x H x D) 1170 x 658 x 99 mm
Weight 77.2 lb (35.0 kg)

HD Models
Model Number TH-42PX20U/P
Chassis GPH6D
Panel Screen Size HD type 42" 16 x 9 (920 x 518 mm)
Number of H 1024 x 768 (VGA)
Pixels
Number of Dots H 3072 x V 768
Pixel Size W 0.90 x H 0.645 mm
Drive Method AC Type Sub Field Drive System, Variable sub Field
Power Source AC 120V 50 /60 Hz
Power Consumption 295W Standby (P. Save on) 1.8W, (P. Save Off) 0.8W
Power Off 0.6W
Applicable Signals NTSC
525i (480i), 525p (480p), 625i (575i), 625p (575p),
750p (720p), 1125 (1080)/60i, 50i, 24p, 24sf, 1250
(1080)/50i
VGA, SVGA, XGA, SXGA, UXGA
Contrast 3000:1
Dimensions (W x H x D) 1020 x 610 x 89 mm
Weight 90.4 lb (41Kg)

9
New Features and Circuit Improvements
Integrated NTSC Tuner
3/2 Pulldown circuit
Plasma Contrast Auto Tracking System (C.A.T.S.)
Picture-in-Picture

SD models