2.1.1. Leakage current cold check1. Unplug the AC cord and connect a jumper between the twoprongs on the plug.2. Measure the resistance value, with an ohmmeter, betweenthe jumpered AC plug and each exposed metallic cabinetpart on the equipment such as screwheads, connectors,control shafts, etc. When the exposed metallic part has areturn path to the chassis, the reading should be between1MΩ and 5.2MΩ.When the exposed metal does not have a return path tothe chassis, the reading must be .Figure 12.1.2. Leakage current hot check(See Figure 1 .)1. Plug the AC cord directly into the AC outlet. Do not use anisolation transformer for this check.2. Connect a 1.5kΩ, 10 watts resistor, in parallel with a 0.15μFcapacitors, between each exposed metallic part on the setand a good earth ground such as a water pipe, as shown inFigure 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 of theabove measuremen ts.6. The potential at any point should not exceed 0.75 voltsRMS. A leakage current tester (Simpson Model 229 orequivalent) may be used to make the hot checks, leakagecurrent must not exceed 1/2 milliampere. In case ameasuremen t is outside of the limits specified, there is apossibility of a shock hazard, and the equipment should berepaired and rechecked before it is returned to thecustomer.2 Safety precautions2.1. 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 customer from being exposed to shock hazards.2.2. Caution for fuse replacement6DMR-ES30VP / DMR-ES30VPC
