Panasonic TC26LX20 - 26" LCD TV Technical Manual Download Page 42 | Manualshive

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Troubleshooting

tended to serve as an aid in the fault isolation, troubleshooting, and

ult of an error or a problem that may occur either

uring operation or while entering Self Check mode.

This section is in
repair of the LCD TV combo or LH34 chassis type in general. These include the TC-
22LR30 and TC-26/32LX20 models. These are some of the screen display symptoms
and conditions that may arise as a res
d

Symptom Display Chart

Table 4

37

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Summary of Contents for TC26LX20 - 26" LCD TV

Page 1: ... B19 Technical Guide LCD High Definition TV Models TC 26LX20 TC 32LX20 and Combo Model TC 22LR30 LH 34 Chassis Functional Overview Circuit Description and Troubleshooting Panasonic Services Company National Training ...

Page 2: ...ed Unauthorized copying and distribution is a violation of law 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 b...

Page 3: ...tem Control Block 7 A Board TC 22LR30 9 H Board TC 26 32LX20 10 K board TC 22LR30 TC 26 32LX20 11 A Board TC 26 32LX20 12 Power Supply 13 Power Supply TC 22LR30 13 P Board Primary Power 14 AP Board Secondary Power 15 Tuner FIP Power Supply AP Board 16 Over Current Protection Shutdown Circuits 17 14 Volt Power Down Detect Circuit 18 Over Voltage Protection _ AC Shutdown Latch Circuit 19 Power Suppl...

Page 4: ... Processing 29 Low Voltage Differential Signaling 30 HDMI Signal Path 32 Self Check Function for TV Section 33 Self Check Access 33 Servicing the TV Portion 34 Service Adjustment Mode for TV 34 How to exit Adjustment mode 35 Servicing the DVD 36 Shutdown Problems 38 LED Flashes Three Times 38 LED Flashes Once every 5 seconds 39 LED Flashes Five Times 39 LED Flashes Eight Times 39 Unit shuts down a...

Page 5: ...Appendix 46 Backlighting 46 Inverter Power Supply 46 High Voltage Power Supply 47 Test and Measurement 48 Specifications 49 Combo Overall Specification 49 TV Portion 50 DVD Portion 51 ...

Page 6: ...de examples of typical problems that may have occurred in similar types of circuits Provide updated information about changes reflected in the newer versions of LCD High Definition TVs The TC 22LR30 LCD TV DVD Ram combo is basically a TC 26 32LX20 model with the addition of a DVD Ram The DVD Recorder that has been incorporated in the LCD TV High Definition Combo unit is basically the same as that ...

Page 7: ... LCD models The Pixel Control IC in conjunction with the Main Microcontroller IC located on the DG Board is responsible for controlling the backlighting and the active matrix display addressing Backlight Brightness Control Figure 1 Dynamically balancing the white light produced from the backlight produces a clearer and crisper image Figure 2 2 ...

Page 8: ...made in the luminance distribution in real time Dynamic Image Enhancement Figure 3 3D Y C Separation The luminance and chrominance of the composite video signals are separated using a three dimensional Y C separation circuit commonly known as a Comb Filter Dot noises or phenomena known as dot crawl and cross colors are reduced Figure 4 3 ...

Page 9: ...Multimedia Input ircuit Board P and AP ndary Power Circuit Board AP were changed to incorporate the voltages required to power the DVD Recorder TC 26 32LX20 series can be found in the following areas L The GC3 Global c Microcontroller the Video SW and the Audio SW are same as that of the LCD TV 26 32LX20 D The DVD Digital C B DMR E65 However the software that resides in IC6702 is different The equ...

Page 10: ...ed in the previous online course because the stand or base doesn t have to be removed for removing the rear cover Rear op A TA Tune P A D DG DG Board is located under DV Board H Spk L Spk R V L K DVD DMRE 65 SD Card Reader Figure 5 Table 1 t Number Description RFKZ0214 Extension Cable DG LSEP2163AE PCB Digital Core A LSEP2164B Input Output Switching PCB TA LSEP2191A Tuner PCB L LSEP2233A Digital A...

Page 11: ...d Name Part Num T tended to provide an overview of the interconnection o circuit boards of the TC 22LR30 LCD Combo Unit Circuit Board Interconn Figure 6 SR ber Description RD LSEP2171B PCB DVD MAIN OP LSEP2175A DVD OPERATION PCB SD LSEP2234A SD PCB SR LSEP2235A SD JOINT PCB M8 RD DKK005 DVD DIGITAL PCB Table 2 6 ...

Page 12: ... supply which is incorporated within the LCD Panel OSD Timing Compensator synchronizes the OSD with the incoming video System Shutdown The Main Micro on the DG board is responsible for monitoring the various shutdown conditions The Main Micro monitors the SOS and main voltage Zero X Detect detection signals via the DG2 connector LED Functions o The Time Warp Led indicates that the DVD is recording...

Page 13: ...System Control Signals Figure 7 8 ...

Page 14: ...ut for processing by the Sound Control IC2301 The MTS IC3103 performs stereo separation of the tuner s multiplex signal and sends the output to the audio switch The TA tuner board on the TC 22LR30 provides the same functionality as the B tuner board found on the TC26 32LX20 The output is connected to the A board via connector PA7 The HDMI interface which resides on the DV board processes and conve...

Page 15: ...els TC 26 32LX20 is comprised of an S Video and Composite video input connection two Component video inputs a DVI audio input and an Audio output connection This board has been merged onto the A board of the TC 22LR30 Combo unit Figure 9 10 ...

Page 16: ...TC 26 32LX20 The K board contains the TV ON Off Volume and Channel select buttons and an additional S Video and Composite video input connector and headphone jack It connects to the A board via connector K3 Figure 10 11 ...

Page 17: ...A Board TC 26 32LX20 The A board for the TC 22LR30 Combo unit is very similar to that of the TC 26 32LX20 model The H board has been merged onto this model s A Board A Board TC26 32LX20 Figure 11 12 ...

Page 18: ...e LCD panel Newer models such as the TC 22LR30 use a 15 volts source that feeds this circuit DC to AC inverter However the TC 26 32LX20 and TC 32LH models use 120 volts as input for the backlight circuitry of their LCD panel The AP Board is responsible for supplying all secondary voltages required for operation Modifications were made on the TC26 32LX20 models AP board to accommodate the voltages ...

Page 19: ... T7001 The voltage on pin 3 of this IC causes it to oscillate and output a PWM pulse to drive the transformer T7001 As a result energy is built and released from the transformer The AC output at pin 11 and 14 of the transformer is rectified into 14 volts to serve as the primary source for all other voltages After the power supply starts running the Run Supply for IC7003 is supplied by diode D7033 ...

Page 20: ...tage to the Audio AMP Circuitry located on the A board When a MAIN_ON signal 3 3V from Pin 69 of Microcontroller IC1106 is issued to this board to turn off the Main power MAIN 12V 9V 3 3V 2 5V the MAIN_ON signal is converted to MAIN_ON_ACT to turn off Regulators IC801 IC806 Q801 Q803 which in turn terminates the Main power During normal operation the MAIN_ON_ACT signal L provides an enable to regu...

Page 21: ...e startup resistor R815 Current flow through Q808 and the primary of the transformer causes a magnetic buildup in the transformer When the transistor reaches saturation and current stops to flow the output current at the other windings of the transformer is rectified into DC voltages that are used by the tuner and the FIP To restart the operation of the circuit feedback current is provided to Q808...

Page 22: ...nnected to a positive B source Under normal conditions the diode is reverse biased which keeps the base of Q832 high However if there is a short or excessive load on the Main 9V line that is being monitored the diode conducts creating a current path for the base bias of Q832 The transistor turns on and allows 3 3V to output at the collector This voltage is then provided to the base of transistor Q...

Page 23: ...n pin T power supply P board and the Sub_5V of the AP board Under normal operation 5 of the connector DG2 supplies a High to pin 61 of the MPU IC1106 If for any reason the Sub_5V or 14 Volts lines drop or disappear pin 5 of the connector DG2 becomes low level to trigger a complete shut down of the unit Figure 16 18 ...

Page 24: ...r up the unit AC Shutdown Latch Circuit ransistor Q822 monitors the Sub_ 3 3V Sub_9V Main_11 2V DVD_5 9V and ease 3 Figure 17 T DVD_1 8V Drive 12V Sub_5V and Sub_9V lines If any of these supply lines incr in voltage transistor Q822 goes into conduction causing its collector to go low As a result Q823 conducts causing the AC _On voltage to drop Transistor Q822 and Q82 form a latch that keeps the un...

Page 25: ... Newer models such as the TC 22LR30 use a 15volt source that feeds this circuit DC to AC inverter However the TC 26 32LX20 and TC 32LH models use 120 volts as input to this circuit P board TC 32LH TC 26 32LX20 Primary Power The Primary power supply is responsible for generating the following The primary source voltage 24 volts for the secondary power supply The 7 volt standby voltage for the syste...

Page 26: ...nd Q7014 to activate relay RL7002 The DC level is then boosted to 380Vdc by the Power Factor Control PFC circuit IC7002 The power factor control circuit is made up of an oscillator used to control the charge and discharge time of the transformer T7001 Start up voltage for the circuit is obtained at the output of the D7002 As the PWM pulses are output from IC7002 the transistors Q7003 and Q7004 are...

Page 27: ...age oscillator circuit that develops the 121 volts needed to drive the LCD backlight Operation begins with the discharge of transformer T7002 The diode D7018 rectifies the AC voltage from the secondary of the transformer Approximately 30 1Vdc from the diode passes through the photo coupler IC7005 and D7011 Figure 19 T7004 22 ...

Page 28: ...ction of IC7005 and IC7006 See Figure 20 The 120V_Stop line is designed to stop the operation of the backlight DC to DC converter if there is a drop or an increase in the 24 volts supply to the AP board Pin 2 of the connector P1 AP10 inputs a High to the P board causing the transistors Q7008 and Q7009 to turn on This causes IC7006 to immediately turn on and short pins 6 and 7 of IC7001 This action...

Page 29: ...This is a simplified overview of the activity that occurs within the primary power supply section when the unit is turned on Figure 20 Figure 21 24 ...

Page 30: ...rd on the designated connector The various voltages derived are used to power the DG board the Audio Control circuitry and the Tuner If the 24volts shuts down a 120volt stop signal is generated which causes the unit to shutdown AP Board TC 26 32LX20 P Board Secondary Power Supply Figure 22 25 ...

Page 31: ...de power to the DG board IC80 provides a regulated 9 volts to IC808 which serves as the voltage source for the tune Its output is 30 volts The Main 9 10 and 12 4 volts supply the secondary source vol to the rest of the unit 2 r tage Secondary Voltages Figure 23 24V 26 ...

Page 32: ...ely switched for video processing on the DG board Connectors PA1 and DG1 serve as the signal access point Video read from the SD Card is processed by the DVD main unit M8 and RD where it enters the Video switch as DVD component Y Pb Pr video Its output appears on connector PA1 as Main Y Pb Pr video where it enters the DG board on connector DG1 pins 37 35 and 33 HDMI video from the DV board enters ...

Page 33: ...aling Processing IC4002 The Microcontroller IC1106 DG board controls the incoming video signals on the Combo Unit TC22LR30 in the same way as it does on the TC 26 32LX20 The difference however is the addition of a serial data line between IC1106 and the Microcontroller IC7501 located on the DVD RD board The main Microcontro Provides Channel selection Global Core control Sound volume control OSD Di...

Page 34: ...comb filter in IC40 converts the composite video signal of the main picture to Y and C separated vide data The S Video signal which is already Y C separated by Chroma information is then applied to the Chroma Demodulator circuit that separates the color signal into PB and PR data The Component inputs which are already Y C separated are converted to digita bypass the comb filter section of this IC4...

Page 35: ...ial Signaling LVDS LVDS devices typically consume less power than other signaling systems such as TTL LVDS devic use a constant current driver Therefore power consumption is independent of frequency The LVDS interface voltage is much less than TTL approximately 2V The voltage swing is typically 350mV with a L In this application three 8 bit streams of data are converted from parallel to serial and...

Page 36: ...31 Figure 28 ...

Page 37: ...og via IC5006 and IC5007 EEPROM IC5001 serves as the content protection circuit and monitors the HDMI signal for copyright protection IC5005 selects between HDMI and DVI audio Note If the external device has DVI output only use a DVI to HDMI adaptor cable in order to connect to the HDMI jack to the DV HDMI connector Also connect the Audio Out signal from the external device set top box or DVD play...

Page 38: ...al Core IC s the MTS the Sound circuit and the Audio Video switches However it should be noted that the displayed results could be misleading by indicating that it is OK The troubleshooting section of this document is intended to provide the necessary guidance and assistance in the fault isolation of a particular problem and will serve as a diagnostic tool for troubleshooting Self Check Access To ...

Page 39: ... Use the number buttons 3 and 4 on the remote control to cycle through the Sub Items until the proper adjustment is reached Adjustment of the Sub Item is made using the Volume buttons on the remote control Data changes are saved automatically when you switch Sub or Main Items or if you exit the service mode Note When the DVD adjustments are accessed the unit switches to the DVD mode The software v...

Page 40: ...YGAIN Video level RF Video Component D 7D DV B Y Video level RF Video Component 96 DVD MAIN R Y Video level RF Video Component DVD 52 ANGL R Y demodulation axis 20 BYGN B Y gain A6 BRIGHT Sub bright 7B COLOR Sub color 54 TINT Sub tint 6A BACK L Sub backlight C0 R CUT 3C G CUT 3C SU B CUT 3C B RED Panel Luminance Color Temperature AD GREEN Panel Luminance Color Temperature AD GAMMA BLUE Panel Lumin...

Page 41: ...or the RD Board side es to the M8 Board side hes to the RD Board side xtension Cable Servicing the DVD Service Tools his is a list of the service equipment that T portion of the LCD TV Combo DVD Test Disc DVDT S01 and DVDT S15 Supplied from SPC Extension Ca repair of Circuit Board M8 Data change CD R Not supplied as se repair of Circuit Board M8 M8 Circuit Board R in IC6702 This converts TC 22LR30...

Page 42: ...t may occur either uring operation or while entering Self Check mode This section is in repair of the LCD TV combo or LH34 chassis type in general These include the TC 22LR30 and TC 26 32LX20 models These are some of the screen display symptoms and conditions that may arise as a res d Symptom Display Chart Table 4 37 ...

Page 43: ...fferent models and will be included his document D Flashes Three Times No Yes No Yes Is the Drive the AP board 12Volts present on pin 4 of connector PAP7 of Check regulator IC805 on The AP Board Is the Sub 9V present on pins 9 10 of connector PAP5 of the AP board END Check regulator IC 809 on the AP Board Is the Drive 5 Volts present on pin 8 of Q804 or TP842 of the AP board Check pin 2 of regulat...

Page 44: ...nit shuts down and the Power on LED is off SOS Shutdown Problem seconds Check the Backlight supply vol ge from the P board ta TC22LR30 15 volts P2 pin 9 15 Ground pins 1 7 TC26 32LX20 120 volts P4 pins 1 2 Ground Pins 4 7 Check the Main 9Volts Regulator Q801 on the AP Board Check the Sub 5 Volts regulator IC808 If the unit keeps shutting dow Shutdown line at pin 9 of connector DG2 It should be at ...

Page 45: ...ector P7402 on the RD Board Chroma out Pin 18 Luminance out Pin 22 Pin 26 G Y B PB ou R P OK Check connector PA12 on the A board for video Pin 1 Y IN Pin 3 C IN Pin 5 PY IN Pin 7 PB IN Pin 9 PR IN NG The DVD RD Board is most likely defective Check the video interface IC3001 and the surrounding circuitry OK Continued on next page out pin 26 t Pin 34 R out Pin 30 NG Perform a Secondary Power supply ...

Page 46: ...D board Pin 58 R OUT Pin 62 L OUT NG Perform Primary Power ply Check Sup Circuit Board M8 or DVD RAM Drive is defective OK OK NG Check IC40 surr 01 and ounding circuit on the M8 board OK Check the PA1 A Pin 5 L IN Pin 7 R IN 0 on Circuit Board Circuit Bo Check IC3102 and t ard A is defective he surrounding circuit Th Chec and Continued from last page e k t A board is defective he video switch IC31...

Page 47: ...ply circuit OK Check for Chroma pin50 Video pin 51 and Luminance pin52 of IC3101 on the A board NG Replace IC3101 Check for Chro Video on pin 3 an ma on pin 1 d Luminance on pin 5 on connector PA11 of the A Board NG Check the signal line between PA11 and IC3101 OK Check pins 1 and 2 on connector n the RD board P7402 o NG Check IC3001 and surrounding circuit on Circuit Board RD OK Check the Circuit...

Page 48: ...oard Left channel out pin27 and Right channel out pin28 on on NG Perform a Primary Power Supply Check Replace IC3102 OK OK NG Check the audio interface c Board OK IC4001 and surrounding ircuitry on the DVD RD Check pin 1 DVD left in and pin 3 DVD right in on connector the A Board PA10 on Check pin 48 and 50 for analog audio in on connector P7402 on the DVD RD board OK Check the DVD M8 Digital bo D...

Page 49: ... IC1106 on the DG Board Check the voltage at TP7013 14V NG Repair the Sub power circuit on the P board OK Check the 120V_ON_ACT signal at Pin 14 of PP4 It should be approx 0V NG Check the Voltage at Pin 43 on connector PAP2 0V OK Confirm IC1106 on Circuit Board DG OK NG Repair the Main power circuit on the P board OK Che TP7016 15V ck the voltage at Confirm the DC On Off circuit on the AP board is...

Page 50: ...P DR_P_ONH H 5V L 0V Pin 16 1 Check the R858 860 870 871 872 859 861 873 874 899 D841 and D842 NG OK Confirm the voltage at R870 and R873 3V NG C regula 0V L 0V PANEL_ACT H 2 4V L 0V DR_P_ON T H 2 4V L 0V P_ON_ACT H 2 4V L 0V OK onfirm the power control signals to each MAIN_ACT H 2 4V L SUB_ACT H 2 4V tor _AC OK Confirm the output voltage from each regulator IC NG Replace the Regulator IC OK There...

Page 51: ...d off using the input or an enable disable line from the Microprocessor Unit MPU to contr cycle is lengthened to increase the brightness and reduced to decrease the brightness One of the major advantages of pulse width modulation is the off and full starting voltage is always applied to the tube s assuming nominal input voltage Figure 5 is a simplified diagram of a pul DC to AC inverter klighting ...

Page 52: ...dc input which provides for good power transfer The type of circuit depicted in Figure 6 inherently produces a pure sine wave output but the voltage and current waveforms are both distorted when they are applied to a CCF tube which is a highly nonlinear device The transition from the starting voltage to the operating v ented by a small internal series output ca st pro g imped er tube current a en ...

Page 53: ...added to the inverse waveform on the oscilloscope Output waveform This is what the typical output current waveform should look like as viewed in the above test arrangement This is a basic test output voltage to th lo differentially with the probe grounds connected and floating as depicted in the diagram Figure 7 indicates how an oscilloscope can be used for achieving these measurement Figure 34 of...

Page 54: ...JPEG TIFF DPOF Table 5 Still Picture Play SD Card DVD RAM DVD R Recordable Discs DVD RAM DVD R DVD Video CD Audio Video CD DVD AUDIO CD R CD RW Discs Played Disc Type New LCD AI LCD AI Adaptive Brightness Intensifier W XGA 1280 x 720 Pixel 16 M sec Response speed Slot 22 26 32 inch Screen Size 49 ...

Page 55: ...50 V Portion T Table 6 50 ...

Page 56: ...DVD Portion r very similar to the DMR E65 The LCD Combo unit uses a DVD recorde Table 7 51 ...

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