Panasonic TC26LX20 - 26" LCD TV Quick start guide

PASC050803TG1
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

Prepared by
Gerry Gaimo and Jean Magloire
Panasonic Services Company
National Training
"HDMI, the HDMI logo and High-Definition Multimedia Interface are trademarks or registered trademarks of HDMI Licensing LLC."
BBE, the BBE logo, Sonic Maximizer and High Definition Sound are registered trademarks or trademarks of BBE Sound, Inc.
Copyright ©2005 by Panasonic Services Company
A
ll rights reserved. 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 b
y
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.

Table of Contents
Objective........................................................................................................................1
Features.........................................................................................................................2
LCD Technology............................................................................................................2
Dynamic Image Balancing............................................................................................3
3D Y/C Separation.........................................................................................................3
LCD High Definition TV Model Differences.................................................................4
Differences between Models........................................................................................4
Circuit Board Layout.....................................................................................................5
TC-22LR30 Circuit Boards............................................................................................5
Circuit Board Interconnection......................................................................................6
System 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 Supply (TC-26/32LX20)....................................................................................20
P board (TC-32LH, TC-26/32LX20) - Primary Power.............................................20

Standby Power Supply............................................................................................21
Primary Power Supply.............................................................................................21
Power Supply Operation (TC-32LH, TC-26/32LX20)..............................................22
Power On Operation of the DC-to- DC converter..................................................22
Power Off Operation of the DC-to-DC converter...................................................23
Protection of the DC-to-DC converter....................................................................23
AP Board - Secondary Power Supply ....................................................................25
Secondary Voltages...............................................................................................26
Video Circuit Explanation...........................................................................................27
A Board........................................................................................................................27
DG Board .....................................................................................................................28
Video Signal Processing ............................................................................................28
Video Signal 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 and the Power on LED is off........................................................39
SOS Shutdown Problem........................................................................................39
Does Not Record Video to Disc .................................................................................42
Does Not Record Audio to Disc.................................................................................43
Primary Power Supply Check ....................................................................................44
Secondary Power Supply Check ...............................................................................45

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

Objective
This technical guide was prepared with the following objectives in mind:
• Provide the servicer with a brief overview of the concepts of operation for new
circuits employed in this line of models
• Provide drawings with emphasis on the signal path to simplify the task of signal
tracing and to locate the cause of a defect
• Furnish troubleshooting procedures that contribute to a expeditious repair of the
product
• Provide 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 of the DMR-E65.The equipment used for servicing the
DMR-E65 is same as the one used for servicing this model’s DVD-RAM Drive .The only
difference is that the DVD Recorder (DMR) has been downsized to a physically smaller
drive.
1

Features
LCD Technology
The LCD AI (Artificial Intelligence) technology incorporated within this model is very
similar to that covered in previous 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

Dynamic Image Balancing
Enhancements have been made in the LCD AI technology as newer units evolve. This
is an example of the improvements 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

LCD High Definition TV Model Differences
Differences between Models
The significant differences between models associated with the TC-22LR30 combo unit
CD TV Section ore IC series that are used for the Video Signal processing, the (TC-
VD-RAM Section .A. (Circuit Board M8) is the same as that of the DVD Recorder
for servicing
ircuit Board A put signal lines for the DVD Recorder Circuit were added to the Video
utput signal lines for the DVD Recorder Circuit were added to the Audio
Audio Signal Process (IC3299) was added to record SAP to the DVD.
ircuit Board DG troller (IC1106) software was modified from the previous model to
ircuit Board RD (Main DVD Bd.) ommodate DVD Recorder.
ircuit Board M8 (DVD Digital Bd.) modate the DVD Recorder. The on the DMR-
ircuit Board DV (HDMI Interface) mmodate the High Definition 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 equipment used for servicing the DMR-E65 is same as the one used
this model’s DVD-RAM Drive .The only difference is that the DVD Recorder (DMR) has
been downsized to a physically smaller drive.
C
The input and out
SW (IC3101).
The input and o
SW (IC3102).
The MTS/SAP
C
The Main Micro con
incorporate communication with the DVD Recorder Circuit.
C
This Circuit Board was added to acc
C
This Circuit Board was added to accom
Microcontroller (IC6001) on this Board is identical to the one that resides
E65 Controller board and functions accordingly.
C
This Circuit Board was added to acco
(HDMI).
C
The Primary (P) and Seco
4

Circuit Board Layout
C-22LR30 Circui
similar to that of the TC-26/32LX20 and is
omprised of the following boards along with their associated part numbers as shown in
en view TC-22LR30
TV Portion Circuit Board Description
Board Name Par
T
t Boards
The TV portion of the combo unit is very
c
this figure. Disassembly of this unit is much easier than the disassembly of the unit
covered 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
S
p
k LS
p
k R
V
L
K
DVD DMRE- 65
SD Card Reader
Figure 5
Table 1
t Number Description
RFKZ0214 Extension Cable
DG LSEP2163AE PCBDigital Core
ALSEP2164B Input/Output Switching PCB
TA LSEP2191A Tuner PCB
LLSEP2233A Digital Audio Jack PCB
VLSEP2169B Front PCB
PLSEP2189A AC-DC Power PCB
AP LSEP2232A DC-DC Power PCB
HA BLSEP2199A HDMI Audio Jack PC
DV TNPA3162AB HDMI PCB
K LSEP2170B Top Operation PCB
5

Circuit Board Interconnection
his diagram is in f the various
ection
DVD Portion Circuit Board Description
Board 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 PCBDVD MAIN
OP LSEP2175A DVD OPERATION PCB
SD LSEP2234A SD PCB
SR LSEP2235A SD JOINT PCB
M8 RD-DKK005- DVD DIGITAL PCB
Table 2
6

System Control Block
The control signals responsible for the overall operation and control of both units are
shown in this diagram along with their designated termination points.
 Main Power switch signal is derived from the power on switch, which is located on
the K board. The Main Micro (TV Microcontroller), located on the DG board, sees
this as a “key scan” input signal and issues a TV ON and AC_On to the control
circuitry within the Primary and secondary power supply.
 DVD Power switch signal is derived from the DVD operation switch, located on the
DVD OP board. This signal is responsible for initiating the power on sequence for
the DVD operation. The Main Micro sees this as a “key scan” input signal.
 Panel ON signal appears on pin 28 of the DG board connector DG2. This is
equivalent to an on/off switch for the LCD Panel.
 Backlight ON /OFF (B/L On/Off) signal provides the enable for the DC to AC
backlight inverter power 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 at twice the normal
record mode (operator’s choice)
o The SD LED indicates that the SD card is being accessed either for a read or
a write operation
o The DVD LED indicates that the DVD unit is being accessed either for a read
or a write operation
 TV Data In/Out are DVD control lines used for playback and record.
 DVD Play switches the audio monitor output from all audio inputs to the DVD
Output.
 Wake Up provides Serial data communication between the DVD Micro and Main
Micro.
 Fan Control is accomplished through the use of a fan control circuit located on the
DVD main circuit board. A PWM output signal from sub processor IC 7501 controls
the speed of the fan, based on the internal ambient temperature of the unit
7

System Control Signals
Figure 7
8

Circuit Board Description
A Board (TC-22LR30)
The A board serves as the main board and is comprised of the following:
 The Video Switch IC3101 is responsible for selectively switching all video inputs
(Component, Composite, S-Video and HDMI). The selected input is fed to the
DG Board via the connector A1.
 The Audio Switch (IC3102) selects the desired audio input 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 converts the
digital video and audio signals to analog and outputs them to the DG board via
the video switch. A board TC22LR30
IC3103
IC3102
IC3101
Figure 8
9

H Board (TC-26/32LX20)
The H Board on models 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

K board (TC-22LR30, 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

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

Power Supply
Power Supply (TC-22LR30)
The power source for all models is comprised of a Primary and Secondary power
supply. The P Board is responsible for generating the primary source voltage used to
supply power to the secondary power supply, located on the AP board. It also supplies
the voltage that feeds the backlighting circuitry, which is incorporated on the 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 required to power up the DVD RAM, which was basically
added to the TC-26/32LX20 to make it into a combo unit (TC-22LR30).
P Board TC-22LR30 Combo Model
Figure 12
13

P Board - Primary Power
The Primary power supply is responsible for generating the following:
1. The standby power supply
2. The primary source voltage (14volts) for the secondary power supply.
3. Backlighting voltage (15 Volts) for the TC-22LR30
STANDBY POWER Circuit
The incoming AC voltage passes through the inrush current resistor R7001 and enters
the rectifier circuit consisting of D7015, D7022, D7023, and D7024 for conversion to
DC. The output is then applied to IC7005, a 7volt regulator. The 7volt output of the
regulator is sent to the AP board for conversion into 3.3V. This 3.3V is provided to the
DG board via pin 44 of the connector PAP2 to serve as standby voltage for the system
control circuit.
14V POWER SUPPLY
When a power up command is sent by the system control IC (Main Micro IC1106 on the
DG board), the AC_ON pin 47(connector PAP4 pin 13) sends a high to transistors
Q7002 and Q7003 to activate the power relay RL7001. AC passes through the relay
and enters the bridge rectifier consisting of D7005, D7007, D7008, and D7011.
The diodes convert the AC voltage into DC, which is then applied to pin 3 of IC7003 via
the transformer 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 connected to pin 8 of a secondary
winding of T7001. AC voltage from pin 8 of the transformer is also rectified by D7034
and applied to a switching control (regulator) circuit consisting of Q7005. Output of the
switching control IC is tied to pin 4 of IC7003 where it is monitored for over voltage
conditions. Voltage regulation is achieved via the 14V Error Detection circuit, which
consists of IC7006 and IC7008. The output of IC7006 is connected to pin 1 of IC7003,
the same input as the Run Supply.
15V POWER SUPPLY
This circuit generates +15Vdc used on the AP board. This voltage is also used to power
up the DC to AC converter for the backlight of the LCD Panel. The switched 14Volts
(sw+14V., which is generated when the unit is powered up), in conjunction with the
MAIN_ON_ACT (signal (H): approx.3.0V), allows Q7001 to turn on and activate the
Relay (RL7002). The rest of the operation is exactly the same as that of the 14 Volts
power supply.
14

AP Board - Secondary Power
The Secondary power supply is responsible for producing the various voltages that are
required to power the DG board, the A board, the DVD unit and the LCD Panel VCC.
These voltages appear on connectors PAP2, PAP5 and PAP6.
• The 15V supplied from the P Board Connector PAP4 is converted to the
MAIN 12V, which supplies this voltage 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 regulators
IC801, IC806, Q801, and Q803, which provides for the appropriate output of the Main
power. AP Board Secondary Power Supply TC - 22LR30
Figure 13
15