Samsung CHT-420 Service Manual

Also see for CHT-420: Instruction manual Instruction manual Service manual Manual de instrucciones

Contents

Samsung Electronics 1-11. Precautions1-1 Safety Precautions1) Before returning an instrument to the customer,always make a safety check of the entire instrument,including, but not limited to, the following items:(1) Be sure that no built-in protective devices aredefective or have been defeated during servicing.(1)Protective shields are provided to protect boththe technician and the customer. Correctly replaceall missing protective shields, including anyremoved for servicing convenience.(2)When reinstalling the chassis and/or other as-sembly in the cabinet, be sure to put back in placeall protective devices, including, but not limited to,nonmetallic control knobs, insulating fish papers,adjustment and compartment covers/shields, andisolation resistor/capacitor networks. Do not oper-ate this instrument or permit it to be operated with-out all protective devices correctly installed andfunctioning.(2) Be sure that there are no cabinet openings throughwhich adults or children might be able to inserttheir fingers and contact a hazardous voltage. Suchopenings include, but are not limited to, excessive-ly wide cabinet ventilation slots, and an improper-ly fitted and/or incorrectly secured cabinet backcover.(3) Leakage Current Hot Check-With the instrumentcompletely reassembled, plug the AC line corddirectly into a 120V AC outlet. (Do not use an iso-lation transformer during this test.) Use a leakagecurrent tester or a metering system that complieswith American National Standards institute (ANSI)C101.1 Leakage Current for Appliances andUnderwriters Laboratories (UL) 1270 (40.7). Withthe instrument’s AC switch first in the ON positionand then in the OFF position, measure from aknown earth ground (metal water pipe, conduit,etc.) to all exposed metal parts of the instrument(antennas, handle brackets, metal cabinets, screw-heads, metallic overlays, control shafts, etc.), espe-cially any exposed metal parts that offer an electri-cal return path to the chassis.Any current measured must not exceed 0.5mA.Reverse the instrument power cord plug in the out-let and repeat the test. See Fig. 1-1.Any measurements not within the limits specifiedherein indicate a potential shock hazard that mustbe eliminated before returning the instrument tothe customer.Fig. 1-1 AC Leakage Test(4) Insulation Resistance Test Cold Check-(1) Unplugthe power supply cord and connect a jumper wirebetween the two prongs of the plug. (2) Turn on thepower switch of the instrument. (3) Measure theresistance with an ohmmeter between thejumpered AC plug and all exposed metallic cabinetparts on the instrument, such as screwheads,antenna, control shafts, handle brackets, etc. Whenan exposed metallic part has a return path to thechassis, the reading should be between 1 and 5.2megohm. When there is no return path to the chas-sis, the reading must be infinite. If the reading isnot within the limits specified, there is the possibil-ity of a shock hazard, and the instrument must berepared and rechecked before it is returned to thecustomer. See Fig. 1-2.Fig. 1-2 Insulation Resistance TestDEVICEUNDERTEST(READING SHOULDNOT BE ABOVE0.5mA)LEAKAGECURRENTTESTEREARTHGROUNDTEST ALLEXPOSED METERSURFACESALSO TEST WITHPLUG REVERSED(USING AC ADAPTERPLUG AS REQUIRED)2-WIRE CORDAntennaTerminalExposedMetal Partohm ohmmeter