Panasonic TH-42PX20U Service Update Information
  1. Manuals
  2. Brands
  3. Panasonic Manuals
  4. Monitor
  5. TH42PX20U - 42" HDTV PLASMA DISPLAY
  6. Service update information

Panasonic TH-42PX20U Service Update Information

Plasma display panel
Hide thumbs Also See for TH-42PX20U:
Table of Contents

Advertisement

Quick Links

Download this manual
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.
1

Advertisement

Table of Contents
loading

Related Manuals for Panasonic TH-42PX20U

Summary of Contents for Panasonic TH-42PX20U

  • Page 1 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.

  • Page 3: Table Of Contents

    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...
  • Page 4 +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 C Mode ......................59 C Menu Structure..................60 CD mode ......................61...

  • Page 5: Objective

    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.

  • Page 7: Model Line Up

    Model Line Up TH-42PX20U TH-50PX20U 42-inch (106cm) HD Version 50-inch (127 cm) 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...

  • Page 8: Performance Comparison

    Performance Comparison SD Models Chassis GP5D GP6DU Panel Size Pixels (H x V) 852 x 480p 852 x 480p 852 x 480p Brightness Peak (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...

  • Page 9: Specifications

    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...

  • Page 10: New Features And Circuit Improvements

    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 • New Deep Black Front Glass Filter: Improves Contrast Ratio in Lighting Environment by 15% • Super Real Gamma System: Reproduces 1,536 shades of gradation (60Hz) •...

  • Page 11: 42" Sd Pcb Board Layout Diagram

    Figure 2 •Simple and low cost circuit •High performance •Higher brightness 42” SD PCB Board Layout Diagram Figure 2...

  • Page 12: Board Comparison Chart

    Printed Circuit Board Information Table Board Name Function Fuse and Line Filter Circuit Power Supply Circuit DC/DC converter and Audio Amplifier Circuit Remote, Light Receiver and Power LED Circuits Front Switch, PC and Video Input Circuits RGB Digital Processor, Format converter, Plasma AI, Discharge Control Circuits, Sub-Field Processor Scan Signal Drive Circuit SU/SD...

  • Page 13: Video Signal Block Diagram

    Video Signal Block Diagram Figure 3 GP6 series plasma panels incorporate two NTSC tuners. The main tuner is used for primary picture operation. It provides a composite video and a multiplex audio output. The sub-tuner provides only a video output used for multi picture functions.
  • Page 14 interlace to progressive scan conversion. The Global core IC also converts the horizontal frequency of all NTSC inputs to 31.468KHz. The output of the GC2M IC is RGB; it is applied to an external RGB amplifier. IC001 is the TV Main CPU. It generates the On Screen Display (OSD) RGB signals, which also enters the RGB amplifier stage.

  • Page 15: Video Signal Path Explanation

    Video Signal Path Explanation Figure 4 NTSC \ 480i Video Signal Path The TH-42PA20U/P incorporates two NTSC tuners, allowing the simultaneous viewing of two signals. It is also equipped with three NTSC Video inputs and three NTSC S-Video inputs. Tuner-1 produces audio and video signals. Tuner-2 produces video only, as it is the video source intended for use in the “Picture in Picture”...
  • Page 16 Main and Sub Video signals are amplified and applied to another video switching IC, IC4302. The component video signals Y, Pb, and Pr are also input to IC4302 via the connectors located at the rear of the cabinet. The DVI input connector, attached to the DG Board, supplies the DVI signal to the DVI receiver where it undergoes serial to parallel conversion.

  • Page 17: Dvi Input

    DVI Input Figure 5 The DVI (Digital Visual Interface) input is a port designed to receive digital video from a set-top box, a DVD player, or other digital devices. IC5001 converts the digital video to parallel analog RGB video. The HDCP (High-bandwidth digital content protection) circuit monitors the DVI signal for copyright protection.

  • Page 18: Dvi Rgb To Yuv Conversion

    DVI RGB to YUV Conversion Figure 6 IC5102 is an RGB to YUV (Y, Pb, PR) converter. It uses the vertical and horizontal sync pulses of the DVI receiver to convert the analog RGB signal to Y, Pb, Pr component signal. The signal is now in the form of an ATSC signal format that can be processed like any other component signal.

  • Page 19: Digital Processor

    Digital Processor Figure 7 Main Picture On the DG- Board, the main Y, Pb, Pr signals are converted to digital data by an analog to digital (A/D) converter circuit located inside the Global Core IC, IC4501. The comb filter in IC4501 converts the composite video signal of the main picture to Y and C separated video signals.
  • Page 20 then converts the digital signal scan format from interlaced to progressive before sending it back to IC4501. The NR/CTI/DSC circuit reduces noise and improves the picture quality. The 10 bit signals are then converted to analog R, G, and B component signals by IC4501, and applied to the RGB amplifier IC4512.

  • Page 21: Rgb Amplifier

    RGB Amplifier Figure 8 The RGB output of IC4501 and the OSD (On Screen Display) RGB output of the television MPU, IC001 enter the RGB amplifier IC4512. A switching circuit combines the two RGB signals for display on the screen. The Adjust Data section sets the RGB level, matching the required levels for the DG board.

  • Page 22: Rgb/Pc Select

    RGB/PC Select Figure 9 PC RGB Signals are input to the G Board located at the front of the unit. RGB signals from the PC input connector as well as standard RGB signals from the RGB amplifier, IC4512 enter IC8200 for selection. The selected output passes through the LPF circuit consisting of IC8201 to reduce bandwidth.

  • Page 23: D Board Outline

    D Board Outline Figure 10 The D-board consists of the digital signal process circuitry. The analog RGB input is converted to digital by IC9009. The eight bit digital output enters IC9151 for processing. The digital video data is converted to progressive scan and mixed with the OSD data.

  • Page 24: Sync Signal Process

    Sync Signal Process Figure 11 On the DG-Board, the sync signals retrieved from the input device enter the sync switch (IC8071). The selected sync signals are output to the D-Board via pins 31, 32, and 34 of connector DG3/D3. The sync signals then enter a level shifter IC, IC9023, to change the DC Level from 5 to 3.3 volts.

  • Page 25: Sc Board Explanation

    SC Board Explanation Figure 12...
  • Page 26 Figure 13 The SC Board consists of buffers and drivers used to generate the scan signals to the panel. The buffers provide isolation between the D board and the drivers. Connector SC20 provides the drive voltages (140V, 100V and 18V) as well as the trigger signals to switch the FET transistors.
  • Page 27 Figure 14 After the scan waveform is developed on the SC Board, it is applied to the SU and SD boards for de-multiplexing. The signal is input to a series of shift registers inside the PDP scan driver IC. Figure 14 shows an example of the de- multiplexing circuit.

  • Page 28: Ss Board Explanation

    SS Board Explanation Figure 15 After the video signal is processed on the D board, the sustain and erase pulses are output to the SS board. The erase pulse is output at the beginning of each scan period. The pulse is applied to the SS2 and SS3 boards to remove the previous charge for the upper and lower sections of the display panel.
  • Page 29 Figure 16...
  • Page 30 Figure 17 The Sustain pulse is developed using a similar circuit as the Scan Pulse. A series of specifically timed pulses are applied to FET drivers creating the distinctive sustain pulse. The drivers switch the voltages (150V, 155V and 175V) at selected intervals determined by the D board.

  • Page 31: Power Supplies (Gp6D Chassis)

    Power Supplies (GP6D Chassis) Standby power supply Figure 18 The standby power supply provides the necessary DC voltage for the system control Microprocessor, Reset circuit and the EEPROM. D404 rectifies the incoming AC Voltage and applies it to the transformer T402 and the standby B+ control circuit IC401.

  • Page 32: Vsus High Voltage Source

    VSUS High Voltage Source Figure 19 The P-Board contains the drive-voltage oscillator circuit that develops the Vsus voltage needed to operate the Scan and Sustain boards. Operation begins with the 18Vdc supply derived at the main power supply. AC voltage from pin 4 of the secondary of the transformer T502 is rectified filtered and applied to pin 1 of IC550.
  • Page 33 the current increase. This voltage is applied to the non-inverting input of the op- Amp at pin 1 of IC551 for over current protection (OCP). Pin 1 of the IC also monitors the status of the transformer. The network consisting of D555, D551, R575, and C554 rectifies and filters the AC voltage at pin 2 of the secondary of the transformer T501.

  • Page 34: Main Power Supply

    Main Power Supply Figure 20b Most of the DC voltages used throughout the unit are derived from this power supply. The voltage divider circuit consisting of resistors R551, R553 and R556 reduces the output of the PFC circuit to create the startup voltage. This voltage enters pin 4 of IC552 to begin the oscillation.

  • Page 35: Vda And Other Voltage Sources

    Pin 1 of the IC also monitors the status of the transformer. The network consisting of D564, D556, R573, and C553 rectifies and filters the AC voltage at pin 2 of the secondary of the transformer T501. The output voltage enters pin 1 of the IC for transformer sensing.
  • Page 36 The +15V source The 15V source is primarily used in the A-Board. It is applied to regulator IC7502 and IC7503 to obtain 9.2V and 5V output. The diode D560 rectifies the AC output of the secondary winding of the transformer T502 to 15Vdc. The other +12V and +5V sources The diode D573 rectifies the AC output of the secondary windings of the transformer T502 to 12Vdc.

  • Page 37: Protection Circuits

    Protection Circuits Figure 21 Protection circuits are incorporated in the unit to prevent the failure of a single circuit or component from creating catastrophic damage. Transistor Q7541 monitors the UNR21V, UNR14V, +9(S)V, and +5(S)V line. If any of these supply lines develop a short circuit, transistor Q7541 goes into conduction and applies a high to pin 69 of the MPU, IC001, triggering an SOS condition.
  • Page 38 The Unregulated 15V and 1.8V lines are monitored for a voltage decrease. Under normal conditions, the voltage drop derived from the voltage divider circuits at the base of Q9714 or Q9716 is enough to turn the transistor on. However should the voltage drop decrease, Q9716 or Q9714 respectively, turn off, allowing the 5 volts at their collectors to forward bias transistor Q9715.

  • Page 39: System Control Circuit

    System Control Circuit Panel Operations Figure 22 This main CPU, IC9701 uses three different I C bus lines to control peripheral devices. Bus line 1 controls the operation of the EEPROM. Programmable setting such as drive settings or white balance is stored in the EEPROM, IC9702. Bus line 2 controls the video processing, main tuner and the sub tuner.

  • Page 40: Tv Operations

    TV Operations Figure 23 IC001 acts as the TV microprocessor, controlling the tuner, video and sound functions. Information such as channel mapping or customer preferences is stored in the EEPROM IC002. I C bus lines 1 and 2 are primarily responsible for video and audio operation.

  • Page 41: Diagnostic Procedures

    Diagnostic Procedures In some cases, the front panel LED will flash a pattern indicating the circuit that has failed. Be sure to record the pattern displayed at start-up. Number of Failed Circuit(s) Detection Note Suspected LED Flashes Point Board(s) Main Micro power IC9709 Voltage P Board...

  • Page 42: Diagnostic Flow Charts

    Diagnostic Flow Charts No Power There are three states of “No Power” indication by the power LED: The power LED does not light up. The power LED is green at power up. It then turns red a few seconds later and blinks on and off.

  • Page 43: No Picture Flowchart 1

    No Picture Flowchart 1 Is the On screen Display information visible? Is the SC Board LED illuminated? Is the SS Board LED SC Board is probably illuminated? defective. D Board is Does the probably SS Board is problem exist on all inputs? defective.

  • Page 44: No Picture Flowchart 2

    No picture Flowchart 2 Are the video signals correct at the DG board input? Reference the H and DG board troubleshooting charts Is the SC board LED lit? The SC board is suspected to be defective. Is the TPSC1 Waveform incorrect? The D Board is suspected to be defective.

  • Page 45: Dark Picture Flowchart

    Dark picture Flowchart Are the video signals correct at the D Board input? Reference the DG Board troubleshooting charts Are the SS board LEDs lit? The SS board is suspected to be defective. Is the TPSS1 Waveform incorrect? The D Board is suspected to be defective.

  • Page 46: Local Screen Failure

    Local screen failure The Plasma Display Panel unit may develop a failure, where the symptom is localized in a particular area of the screen. The figure below can help localize the circuit board that is most likely to be defective. In the example in figure 24, one of the two boards, C2 and D is likely to be the cause.

  • Page 47: Service Hints

    Service Hints Symptom: No picture (black Screen) Suggestion: The use of a magnifying glass can help localize the defective printed circuit board. Use the magnifying glass to take a close look at the pixels of the screen. 1. If the pixels are totally dark, the defect is most likely located in one of the following boards: a) SC-Board...
  • Page 48 Symptom: No picture (black Screen) Figure 28 Suggestion: The use of a magnifying glass can help localize the defective printed circuit board. Use the magnifying glass to take a close look at the pixels of the screen. If the pixels are faintly lit, the defect is most likely located in one of the following boards: A) SS-Board B) SS2-Board...
  • Page 49 Suggestions: Check the Scan pulse waveform at TPSC1 of the SC-Board. (Use TPSS1 of the SS-Board to trigger the oscilloscope.) Proceed to check the power sources at connector S S11, and SS12. Verify that the clock and serial data lines from the D-board are present at connector SS23.
  • Page 50 Symptom: Horizontal Black Bar (Completely dark) Note: The use of a magnifying glass can help localize the defective printed circuit board. Use the magnifying glass to take a close look at the pixels in the area of the black bar. 1 If the pixels are totally dark, the defect is most likely located in one of the following Figure 31...
  • Page 51 No OSD but it has video. Suggestion: Check signal on the DG board. Symptom: Burned image (pattern) is visible. Suggestion: Access the CAT mode and activate the scroll bar or run the set with a white raster for at least fifteen minutes. Panasonic Figure 34...

  • Page 52: Adjustments

    Adjustments If the power supply board is replaced the following adjustments are required. +B Set-up Item / Preparation • Input a 100% white signal. • Set the picture mode to Normal and the White Balance to Normal • Adjustments/Confirmation Adjust and confirm the indicated test point below for the specified voltage. Adjustment Name Test Point...

  • Page 53: Driver Set-Up

    Driver Set-up Item / Preparation • Input an APL 100 % white signal. • Set the picture controls to: Picture mode = Normal White Balance = Cool Aspect = 16:9 Adjustments To perform the following adjustments, please refer to the panel information label located on the heat sink of the panel.

  • Page 54: Initialization Pulse Adjust

    Initialization Pulse Adjust Item / Preparation • Input a Crosshatch signal. • Set the picture mode to Normal, and White Balance to Normal Adjustments Adjust the indicated test point for the specified waveform. Use TPSS1 as the trigger source. Test point Volume Level TPSC1 (SC)

  • Page 55: P.c.b. (Printed Circuit Board) Exchange Procedure

    P.C.B. (Printed Circuit Board) exchange procedure 1. Caution Wait 1 minute for the electrolytic capacitors to discharge before removing any PCB from the unit. 2. Quick adjustment after P.C.B. or Panel exchange P.C.B. Item Volume Test point Voltage level Panel All items in this table P Board Vsus...

  • Page 56: Test Point Locations

    Test Point locations Figure 38...

  • Page 57: Serviceman Mode (Electronic Controls)

    Serviceman mode (Electronic Controls) This Plasma Display television uses the I²C Bus circuitry to control functions and replace many mechanical controls. Instead of adjusting mechanical controls individually, many of the control functions are now performed by using “On Screen Display Menu”. (The Serviceman Adjustment Mode.) Note: It is suggested that the technician reads all the way through and understand the following procedure for Entering/Exiting the Serviceman Adjustment Mode.

  • Page 58: Cat (Computer Aided Test) Mode

    Exiting the Serviceman Mode: Press the Power on the receiver (not the remote) until the receiver turns off. The unit momentarily shuts off (for about 5 seconds); then comes back on tuned to channel 3 with a preset level of sound. Important note: If the Action and Power buttons of the television are used to exit the Serviceman mode, any programmed channels, channels caption data, and...

  • Page 59: I C Mode

    C Mode Select the I C mode by pressing the Up/Down button on the remote control from the front page of the CAT menu, and then press the Action button on the remote control. Accessing the I C mode? 1. Select the alignment subject by pressing the 1 or 2 buttons on the remote control.

  • Page 60: I 2 C Menu Structure

    C Menu Structure The values indicated in this flowchart are sampled data. Figure 41...

  • Page 61: Cd Mode

    CD mode Select the CD mode from the front page of the CAT menu by pressing the Up/Down button on the remote control, and then press the Mute button on the remote control for more than 5 sec. MiCom Software version MiCom Software Version 0.11 Factory...

  • Page 62: Sd Mode

    SD Mode Select the SD mode from the front page of the CAT mode by pressing the Up/Down button on the remote control, and then press the Action button on the remote control. Input command History of remote control command Check (Factory use) 23 25 27-- -- -- -- 27 27 27...

  • Page 63: Alignment Procedures

    Alignment Procedures Pedestal Setting Equipment required: RF Video Gray Scale Generator Panel Settings; Picture = Normal, White Balance = Cool, Aspect Ratio = 16:9 Pattern Display: Figure 42 Step 1- Access the R, G and B cutoff settings and set them to “80”. Step 2- Under the Chroma Control setting, Set Gun off to "5"...

  • Page 64: Ntsc White Balance Adjustment

    NTSC White Balance Adjustment Equipment required: NTSC Pattern Generator, Colorimeter Panel Settings; Picture = Standard, Color Temperature = Cool, Aspect Ratio = 16:9 Step 1- Using the Pattern generator; apply a 20 IRE Window pattern signal to the panel. Apply the color sensor to the panel and monitor the values.

  • Page 65: Hd Panel White Balance Adjustment

    HD Panel White Balance Adjustment Equipment required: 720p/1080i Pattern Generator, Colorimeter Panel Settings; Picture = Standard, Color Temperature = Cool, Aspect Ratio = 16:9 Step 1- Using the Pattern generator; apply a 20 IRE Window pattern signal to the panel. Apply the color sensor to the panel and monitor the values.

  • Page 66: Sub Brightness Setting

    Sub Brightness Setting Equipment required: NTSC grayscale pattern Generator Panel Settings; Picture = Normal, Aspect Ratio = 16:9 Pattern Display: Note: Adjust in a Dark room. Step 1- Set the white balance to Cool. Step 2- Access the All cutoff setting in service mode and adjust so that pixel emission starts in the 2% area and there is no emission in the 0% area.

  • Page 67: Hotel Mode Operation

    Hotel Mode Operation Hotel Mode restricts certain operation functions for use in hotels Entry to Hotel Mode 1. Enter the Service Mode using the previously described method. Note: Leave the set tuned to cable channel 124, changing the channel may inhibit access to the Hotel Mode EEPROM address.
  • Page 68 7. Press and hold the Volume Down button of the receiver and press the TV/Video button of the remote control three times within two seconds to display the Hotel Setup menu. Figure 44 Item Function Options INITIAL INPUT The receiver OFF /TV /COMP1 /COMP2 /DIGITAL automatically selects this /VIDEO1 /VIDEO2 /VIDEO3 /PC...
  • Page 69 REMOCON The receiver <Selection>: OFF / ACTION LOCK automatically disables the OFF: No Restrictions selected keys of the Action: Action Button on the remote is remote control every time inhibited power is switched on. 8. Push the Power button of the receiver or the remote control to hide the Serviceman mode menu 9.

  • Page 70: Service Contact Information

    Service Contact Information Panasonic 1-800-211-7262 Customer Call Center Tech Support PTV and Digital Products Hotline 1-800-743-2335 (Authorized Service Centers only) All Other Products 1-800-572-2672 Authorized Service Centers only (access code required) Fax 1-800-348-7315 1-201-392-4207 Non–authorized (limited time access) Other Numbers 1-800-833-9626 Parts Dept.

This manual is also suitable for:

Th-50px20uTh-42pa20uTh-37pa20u

Table of Contents