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 between1Mohm and 5.2Mohm.When the exposed metal does not have a return path tothe chassis, the reading must be .Figure 12.1.2. Leakage Current Hot Check (SeeFigure 1.)1. Plug the AC cord directly into the AC outlet. Do not use anisolation transformer for this check.2. Connect a 1.5kohm, 10 watts resistor, in parallel with a0.15μF capacitors, between each exposed metallic part onthe set and a good earth ground such as a water pipe, asshown in Figure 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 measurements.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 milliamp. In case ameasurement 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 conducting repairs and servicing, do not attempt to modify the equipment, its parts or its materials.2. When wiring units (with cables, flexible cables or lead wires) are supplied as repair parts and only one wire or some of the wireshave been broken or disconnected, do not attempt to repair or re-wire the units. Replace the entire wiring unit instead.3. When conducting repairs and servicing, do not twist the Faston connectors but plug them straight in or unplug them straight out.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.6. After servicing, make the following leakage current checks to prevent the customer from being exposed to shock hazards.5TH-58PE75U
