Panasonic TC-22LR30 Service Manual

Also see for Combo TC-22LR30: Operating instructions Technical guide

Panasonic TC-22LR30 Service Manual Manual pdf 3 page image

1 SAFETY PRECAUTIONS1.1. GENERAL GUIDELINES1. IMPORTANT SAFETY NOTICEThere are special components used in this equipmentwhich are important for safety. These parts are marked byin the Schematic Diagrams, Circuit Board Layout,Exploded Views and Replacement Parts List. It is essentialthat these critical parts should be replaced withmanufacturer’s specified parts to prevent shock, fire, orother hazards. Do not modify the original design withoutpermission of manufacturer.2. An Isolation Transformer should always be used during theservicing of Combination LCD TV/DVD-RAM whose chassisis not isolated from the AC power line. Use a transformer ofadequate power rating as this protects the technician fromaccidents resulting in personal injury from electrical shocks.It will also protect Combination LCD TV/DVD-RAM frombeing damaged by accidental shorting that may occurduring servicing.3. When servicing, observe the original lead dress, especiallythe lead dress in the high voltage circuits. If a short circuit isfound, replace all parts which have been overheated ordamaged by the short circuit.4. After servicing, see to it that all the protective devices suchas insulation barriers, insulation papers, shield, andisolation R-C combinations are properly installed.5. When the TV set is not used for a long period of time,unplug the power cord from the AC outlet.6. After servicing make the following leakage current checks toprevent the customer from being exposed to shockhazards.1.2. LEAKAGE CURRENT COLDCHECK1. Unplug the AC cord and connect a jumper between the twoprongs on the plug.2. For physically operated power switches, turn power on.Otherwise skip step 2.3. Measure the resistance value, with an ohmmeter, betweenthe jumpered AC plug and each exposed metallic cabinetpart on the receiver, such as screwheads, connectors, etc.When the exposed metallic part has a return path to thechassis, the reading should be between 1 MΩ and 8.5 MΩ.When the exposed metal does not have a return path to thechassis, the reading must be infinity.1.3. LEAKAGE CURRENT HOTCHECK1. Plug the AC cord directly into the AC outlet.Do not use a isolation transformer for this check.2. Connect a 1.5 kΩ, 10 W resistor, in parallel with a 0.15 μFcapacitor, between each exposed metallic part on the setand a good earth ground, as shown in Figure 1.3. Use an AC voltmeter, with 1 kΩ/V or more sensitivity, tomeasure 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 of theabove measurements.6. The potential at any point should not exceed 0.75 V RMS.A leakage current tester (Simpson Model 229 equivalent)may be used to make the hot checks. Leakage current mustnot exceed 1/2 mA. In case a measurement is outside ofthe limits specified, there is a possibility of shock hazard,and the receiver should be repaired and rechecked beforeit is returned to the customer.Figure 13TC-22LR30