Panasonic TC-26LX600 Service Manual

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Panasonic TC-26LX600 Service Manual Manual pdf 3 page image

1 Safety precautionsGeneral guidelines1. When servicing, observe the original lead dress. If ashort circuit is found, replace all parts which have beenoverheated or damaged by the short circuit.2. After servicing, see to it that all the protective devicessuch as insulation barriers, insulation papers shields areproperly installed.3. After servicing, make the following leakage currentchecks to prevent the customer from being exposed toshock hazards.Leakage current cold check1. Unplug the AC cord and connect a jumper between thetwo prongs on the plug.2. Measure the resistance value, with an ohmmeter,between the jumpered AC plug and each exposedmetallic cabinet part on the equipment such asscrewheads, connectors, control shafts, etc. When theexposed metallic part has a return path to the chassis,the reading should be between 1M and 5.2M. When theexposed metal does not have a return path to thechassis, the reading must be infinite.Figure 1. Hot check circuitLeakage current hot check1. Plug the AC cord directly into the AC outlet. Do not usean isolation transformer for this check.2. Connect a 1.5k, 10 watts resistor, in parallel with a0.15F capacitors, between each exposed metallic parton the set and a good earth ground such as a waterpipe, as shown in Figure 1.3. Use an AC voltmeter, with 1000 ohms/volt or moresensitivity, to measure the potential across the resistor.4. Check each exposed metallic part, and measure thevoltage at each point.5. Reverse the AC plug in the AC outlet and repeat each ofthe above measurements.6. The potential at any point should not exceed 0.75 voltsRMS. A leakage current tester (Simpson Model 229orequivalent) may be used to make the hot checks,leakage current must not exceed 1/2 milliamp. In case ameasurement is outside of the limits specified, there isa possibility of a shock hazard, and the equipmentshould be repaired and rechecked before it is returnedto the customer.2 Warning2.1. Prevention of Electro StaticDischarge (ESD) toElectrostatically Sensitive (ES)DevicesSome semiconductor (solid state) devices can be damagedeasily by static electricity. Such components commonly arecalled Electrostatically Sensitive (ES) Devices. Examples oftypical ES devices are integrated circuits and some field-effect transistors and semiconductor "chip" components.The following techniques should be used to help reduce theincidence of component damage caused by electro staticdischarge (ESD).1. Immediately before handling any semiconductorcomponent or semiconductor-equipped assembly, drain offany ESD on your body by touching a known earth ground.Alternatively, obtain and wear a commercially availabledischarging ESD wrist strap, which should be removed forpotential shock reasons prior to applying power to the unitunder test.2. After removing an electrical assembly equipped with ESdevices, place the assembly on a conductive surface suchas alminum foil, to prevent electrostatic charge buildup orexposure of the assembly.3. Use only a grounded-tip soldering iron to solder or unsolderES devices.4. Use only an anti-static solder removal device. Some solderremoval devices not classified as "anti-static (ESDprotected)" can generate electrical charge sufficient todamage ES devices.5. Do not use freon-propelled chemicals. These can generateelectrical charges sufficient to damage ES devices.6. Do not remove a replacement ES device from its protectivepackage until immediately before you are ready to install it.(Most replacement ES devices are packaged with leadselectrically shorted together by conductive foam, alminumfoil or comparable conductive material).7. Immediately before removing the protective material fromthe leads of a replacement ES device, touch the protectivematerial to the chassis or circuit assembly into which thedevice will be installed.CautionBe sure no power is applied to the chassis or circuit, andobserve all other safety precautions.8. Minimize bodily motions when handling unpackagedreplacement ES devices. (Otherwise hamless motion suchas the brushing together of your clothes fabric or the liftingof your foot from a carpeted floor can generate staticelectricity (ESD) sufficient to damage an ES device).3