Panasonic TH-49DX400K Service Manual

Panasonic TH-49DX400K Service Manual Manual pdf 2 page image

1 Safety Precautions1.1 General Guidelines1. When servicing, observe the original lead dress. If a short 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 devices such as insulation barriers, insulation papers shields areproperly installed.3. After servicing, make the following leakage current checks to prevent the customer from being exposed toshock hazards.4. When conducting repairs and servicing, do not attempt to modify the equipment, its parts or its materials.5. When wiring units (with cables, flexible cables or lead wires) are supplied as repair parts and only one wire orsome of the wires have been broken or disconnected, do not attempt to repair or re-wire the units. Replace theentire wiring unit instead.6. When conducting repairs and servicing, do not twist the Faston connectors but plug them straight in or unplugthem straight out.1.1.1 Leakage Current Cold Check1. Unplug the AC cord and connect a jumper between the two prongs on the plug.2. Measure the resistance value, with an ohmmeter, between the jumpered AC plug and each exposed metalliccabinet part on the equipment such as screwheads, connectors, control shafts, etc. When the exposed metallicpart has a return path to the chassis, the reading should be 8.5Mohm to 13Mohm.When the exposed metal does not have a return path to the chassis, the reading must be .1.1.2 Leakage Current Hot Check (See Figure 1 .)1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check.2. Connect a 1.5kohm, 10 watts resistor, in parallel with a 0.15μF capacitors, between each exposed metallic parton the set and a good earth ground such as a water pipe, as shown in Figure 1 .3. Use an AC voltmeter, with 1000 ohms/volt or more sensitivity, to measure the potential across the resistor.4. Check each exposed metallic part, and measure the voltage at each point.5. Reverse the AC plug in the AC outlet and repeat each of the above measurements.6. The potential at any point should not exceed 0.75 volts RMS. A leakage current tester (Simpson Model 229 orequivalent) 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 is a possibility of a shock hazard, and the equipmentshould be repaired and rechecked before it is returned to the customer.Figure 1Page 1 of 110/22/2017file://\\royalfs\Service\Technical\Ms.dehghani\All SVC sent by CD\19\TH-49DX400SAL...