Panasonic TX-20LB5F / G / TX-20LB5P / G Service Manual ▷ View online
ORDER NO. PCZ0602001CE
Service Manual
LCD TV
Power Source
AC 100-240V, 50/60Hz TV set DC 15V, 4.67A Max.
Power Consumption
Average use: 50W
Standby
condition:
2.5W
LCD
VGA (640 × 480 pixels)
4:3
aspect
ratio
LCD
panel
Screen Size
408 mm(W) × 306 mm(H)
Sound
Speaker
9 cm × 5cm, 2pcs, 4Ω
Audio
Output
4W (2W + 2W), 20% THD
Headphones
M3 (3.5 mm) Jack x 1
Receiving Systems/ Band name
VHF
BAND I: CH2-CH4
BAND II: CH5-CH12
UHF HYPER BAND :SI’-S3’, S1-S20
BAND
IV,
V
:
CH21-CH68
PAL-B/G, D/K, SECAM-L/L’, NTSC(AV input only)
Aerial-Rear
UHF/VHF
TX-20LB5F/G
TX-20LB5P/G
TX-20LB5P/G
SL-120PP Chassis
Operating Conditions
Temperature: -10°C ~ 40°C
Humidity: 0% ~ 90% RH (non-condensing)
Connection Terminals
AV1
(Scart
connecter)
21 Pin terminal (Audio/Video in, Audio/Video out,
RGB in)
RGB in)
AV2
VIDEO
RCA PIN Type × 1
S-VIDEO
Mini DIN 4-pin
AUDIO
L-R
RCA PIN Type × 2
Dimensions (W x H x D)
Including TV Stand
608mm(W) × 215mm(D) × 457.5mm(H)
TV
Set
Only
608mm(W) × 73,7mm(D) × 403mm(H)
Weight
10.1kg
Net
Note:
Design and Specifications are subject to change without
notice.
Weight and Dimensions shown are approximate.
notice.
Weight and Dimensions shown are approximate.
TX-20LB5F/G
TX-20LB5P/G
TX-20LB5P/G
2
CONTENTS
Page
1. Safety Precautions ----------------------------------------------- 3
1.1. General Guidelines -------------------------------------- 3
1.2.
Touch-Current
Check
------------------------------------ 3
2. Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) Devices ------------------ 4
3 About lead free solder (PbF) --------------------------------- 5
4. Self Check ---------------------------------------------------------- 6
5. Chasis Board Layout -------------------------------------------- 7
6. Before servicing -------------------------------------------------- 8
6.1. Wire dressing ---------------------------------------------- 8
7. Disassembly for service --------------------------------------- 9
7.1. Stand ass´y ------------------------------------------------ 9
7.2. Back cover ------------------------------------------------- 9
7.3.
CTRL
ass´y
-----------------------------------------------10
7.4. LED ass´y -------------------------------------------------10
7.5.
AV
ass´y
---------------------------------------------------- 11
7.6. INVERTER ------------------------------------------------ 11
7.7.
TTL
ass´y
-------------------------------------------------- 11
7.8. Speaker (left and right) --------------------------------- 11
7.9.
Main
ass´y
-------------------------------------------------12
7.10.Panel
LCD
-------------------------------------------------12
Page
8 Service Mode Function ----------------------------------------13
8.1. How to enter SERVICE 1 ------------------------------13
8.2. How to enter SERVICE 2 ------------------------------13
8.3. Option Description --------------------------------------14
9. Conduct Views ---------------------------------------------------16
9.1. Foil Side ---------------------------------------------------16
9.2. Component Side -----------------------------------------18
10. Block and Schematic Diagrams --------------------------20
10.1. Schematic Diagram Notes ---------------------------20
10.2.
Block
Diagram
------------------------------------------21
10.3.
Schematic
Diagram
-----------------------------------22
11. Parts Location & Replacement Parts List -------------28
11.1. Different parts List -------------------------------------28
11.2. Exploded View ------------------------------------------29
11.3. Stand Assy Exploded View --------------------------30
11.4. Packing Exploded Views -----------------------------31
11.5. Electrical Replacement Parts List ------------------32
TX-20LB5F/G
TX-20LB5P/G
TX-20LB5P/G
3
1 Safety Precautions
1.1. General Guidelines
1.
When servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated or
damaged by the short circuit.
damaged by the short circuit.
2.
After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly
installed.
3. After servicing, make the following leakage current checks to prevent the customer from being exposed to shock hazards.
1.2. Touch-Current Check
1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check.
2.
2.
Connect a measuring network for touch currents between each exposed metallic part on the set and a good earth ground such
as a water pipe, as shown in Figure 1.
as a water pipe, as shown in Figure 1.
3. Use Leakage Current Tester (Simpson 228 or equivalent) to measure the potential across the measuring network.
4. Check each exposed metallic part, and measure the voltage at each point.
5. Reserve the AC plug in the AC outlet and repeat each of the above measure.
6.
4. Check each exposed metallic part, and measure the voltage at each point.
5. Reserve the AC plug in the AC outlet and repeat each of the above measure.
6.
The potential at any point (TOUGH CURRENT) expressed as voltage U1 and U2, does not exceed the following values:
For a. c.: U
1
= 35 V (peak) and U
2
= 0.35 V (peak);
For d. c.: U
1
= 1.0 V,
Note:
The limit value of U2 = 0.35 V (peak) for a. c. and U1 = 1.0 V for d. c. correspond to the values 0.7 mA (peak) a. c. and 2.0
mA d. c.
The limit value U1 = 35 V (peak) for a. c. correspond to the value 70 mA (peak) a. c. for frequencies greater than 100 kHz.
mA d. c.
The limit value U1 = 35 V (peak) for a. c. correspond to the value 70 mA (peak) a. c. for frequencies greater than 100 kHz.
7. In case a measurement is out of the limits specified, there is a possibility of a shock hazard, and the equipment should be
repaired and rechecked before it is returned to the customer.
TX-20LB5F/G
TX-20LB5P/G
TX-20LB5P/G
4
2 Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) 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 electro static discharge (ESD).
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 electro static discharge (ESD).
1.
Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off any ESD on your
body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging ESD wrist strap,
which should be removed for potential shock reasons prior to applying power to the unit under test.
body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging ESD wrist strap,
which should be removed for potential shock reasons prior to applying power to the unit under test.
2.
After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as almi-
num foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.
4.
Use only an anti-static solder removal device. Some solder removal devices not classified as „anti-static (ESD protected)” can
generate electrical charge sufficient to damage ES devices.
generate electrical charge sufficient to damage ES devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ES devices.
6.
Do not remove a replacement ES device from its protective package until immediately before you are ready to install it. (Most
replacement ES devices are packaged with leads electrically shorted together by conductive foam, alminum foil or comparable
conductive material).
replacement ES devices are packaged with leads electrically shorted together by conductive foam, alminum foil or comparable
conductive material).
7.
Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material
to the chassis or circuit assembly into which the device will be installed.
Caution
Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
to the chassis or circuit assembly into which the device will be installed.
Caution
Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
8.
Minimize bodily motions when handling unpackaged replacement ES devices. (Otherwise hamless motion such as the brush-
ing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity (ESD) sufficient
to damage an ES device).
ing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity (ESD) sufficient
to damage an ES device).