Panasonic TX-17LX2 Service Manual

Contents

Panasonic TX-17LX2 Service Manual Manual pdf 3 page image

21. Safety Instruction1.1. General Guidelines1. When servicing, observe the original lead dress. If a short circuit is found, replace all partwhich have been overheated or 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 frombeing exposed to shock hazards.1.2. Touch-Current Check1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this chack.2. Connect a measuring network for touch currents between each exposed matallic part onthe set and a good earth ground such as a water pipe, as shown in Figure1.3. Use Leakage Current Tester(Simpson 228 or equivalent) to measure the potential acrossthe measuring network.4. Check each exposed metallic part, and measure the voltage at each point.6. The potential at any point (TOUGH CURRENT) expressed as voltage U 1 and U2, does notexceed the following values:For a. c.: U 1 = 35V(peak) and U2 = 0.35V(peak);For d. c.: U 1 = 1.0V,Note:The limit value of U2 = 0.35V(peak) for a. c. and U1 = 1.0V for d. c. correspond to thevalues 0.7 mA (peak) a. c. and 2.0 mA d. c.The limit value U1 = 35V(peak) for a. c. correspend to the value 70 mA(peark) a. c. forfrequencies greater than 100kHz.7. In case a measurement is out of the limits specified, there is a possibility of a shock hazard, and theequipment should be repaired and rechecked before it is returned to the customer.Measuring network for TOUCH CURRENTSResistance values in ohms( )V: Voltmeter or oscilloscope(r.m.s. or peak reading)Input resistance: 1MInput capacitance: 200 pFFrequency range: 15Hz to 1 MHz and d.c. respectivelyNOTE - Appropriate measures should be taken to obtain the correct value in case of non-sinusoidal waveforms.Figure 1COLDWATER PIPE(EARTHGROUNDTOAPPLIANCESEXPOSEDMETAL PARTS