Panasonic TX-PR37X10 Service Manual

1 Safety Precautions1.1. General Guidelines1. When servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated ordamaged by the short circuit.2. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properlyinstalled.3. After servicing, make the following leakage current checks to prevent the custom er from being exposed to shock hazards.4. When servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated ordamaged by the short circuit.5. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properlyinstalled.After servicing, make the following leakage current checks to prevent the custom er from being exposed to shock hazards.61.2. Touch-Current Check1. Plug the AC cord directly into the AC outlet. Do not use an isolation transform er for this check.2. Connect a measuring network for touch currents between each exposed metallic part on the set and a good earth groundsuch as a w ater 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 (TOUGH CURRENT) expressed as voltage U1 and U2 , does not exceed the following values:For a. c.: U1 = 35 V (peak) and U2 = 0.35 V (peak);For d. c.: U1 = 1.0 V,Note:The limit value of U2 = 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 2.0mA d. c.The limit value U1 = 35 V (peak) for a. c. correspond to the value 70 mA (peak) a.c. for frequencies greater than 100kHz.7. In case a measurement is out of the limits specified, there is a possibility of ashock hazard, and the equipm ent should berepaired and rechecked before it is returned to the customer.Measuring network for TOUCH CURRENTSCOLDWATER PIPE(EARTH GROUND)Rs=1500Q_ L Cs=0.22|j F10kQ-1 k 1---------1Ro=----------------J 5 0 0 Q'U 1 =r= 0 . 0 2 2 | j F ( V )J Q L jJ J U U i i U 1 — |— и . и ^ г ф Г ^ V J | U2 (V)APPLIANCESEXPOSEDMETAL PARTSResistance values in ohms (Q)V: Voltmeter or oscilloscope(r.m.s. or peak reading)Input resistance: > 1 MQInput capacitance: < 200 pFFrequency range: 15 Hz to 1 MHz and d.c. respectivelyNOTE - Appropriate measures should be taken to obtain the correct value in case of non-sinusoidal waveforms.Figure 12