Sanyo FVM4612 Service Manual

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Sanyo FVM4612 Service Manual Manual pdf 3 page image

31 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 betweenthe two prongs on the plug.2. Measure the resistance value, with an ohmmeter,between the jumpered AC plug and each exposedmetallic cabinet part on the equipment such asscrew heads, connectors, control shafts, etc.When the exposed metallic part has a return pathto the chassis, the reading should be 100 Mohmand over. When the exposed metal does not havea 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. Donot use an isolation transformer for this check.2. Connect a 1.5kohm, 10 watts resistor, in parallelwith 0.15μF capacitors, between each exposedmetallic part on the set and a good earth groundsuch as a water pipe, as shown in Figure 1.3. Use an AC voltmeter, with 1000 ohms/volt ormore sensitivity, to measure the potentialacross the resistor.4. Check each exposed metallic part, andmeasure the voltage at each point.5. Reverse the AC plug in the AC outlet andrepeat each of the above measurements.6. The potential at any point should not exceed0.75 volts RMS. A leakage current tester(Simpson Model 229 or equivalent) may beused to make the hot checks, leakage currentmust not exceed 1/2 milliamp. In case ameasurement is outside of the limits specified,there is a possibility of a shock hazard, and theequipment should be repaired and recheckedbefore it is returned to the customer.Figure 1All manuals and user guides at all-guides.com