DOWNLOAD Panasonic TH-49AF1U / TH-49AF1W (serv.man2) Service Manual ↓ Size: 26.72 MB | Pages: 67 in PDF or view online for FREE

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TH-50LFC70U/TH-50LFC70W

1. When conducting repairs and servicing, do not attempt to modify the equipment, its parts or its materials.
2. When wiring units (with cables, flexible cables or lead wires) are supplied as repair parts and only one wire or some of the

wires have been broken or disconnected, do not attempt to repair or re-wire the units. Replace the entire wiring unit instead.

3. When conducting repairs and servicing, do not twist the Fasten connectors but plug them straight in or unplug them straight

out.

4. When servicing, observe the original lead dress. If a short circuit is found, replace all parts have been overheated or damaged

by the short circuit.

5. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly

installed.

6. After servicing, make the following leakage current checks to prevent the customer from being exposed to shock hazards.

1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check.
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.

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. The potential at any point (TOUCH CURRENT) shall not exceed 0.5 MIU.
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.

Figure 1

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TH-50LFC70U/TH-50LFC70W

1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check.
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.

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. The potential at any point (TOUCH CURRENT) expressed as voltage U

1

 and U

2

, 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,

The limit value of U

2

 = 0.35 V (peak) for a. c. and U

1

 = 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 U

1

 = 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.

Figure 1

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TH-50LFC70U/TH-50LFC70W

Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components commonly are called Elec-
trostatically 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 electrostatic 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.

2. After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as alumi-

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.

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, aluminum foil or compara-
ble 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.

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 ham less 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).