NAD VISO FIVE Service Manual

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1-5SERVICING PRECAUTIONSCAUTION : Before servicing the A/V Receiver covered by thisservice data and its supplements and addends, read and follow theSAFETY PRECAUTIONS. NOTE : if unforeseen circumstancescreate conflict between the following servicing precautions and anyof the safety precautions in this publication, always follow the safetyprecautions.Remember Safety First:General Servicing Precautions1. Always unplug the A/V Receiver AC power cord from the ACpower source before:(1) Removing or reinstalling any component, circuit board,module, or any other assembly.(2) Disconnecting or reconnecting any internal electrical plug orother electrical connection.(3) Connecting a test substitute in parallel with an electrolyticcapacitor.Caution : A wrong part substitution or incorrect polarity installationof electrolytic capacitors may result in an explosion hazard.2. Do not spray chemicals on or near this A/V Receiver or any of itsassemblies.3. Unless specified otherwise in this service data, clean electricalcontacts by applying an appropriate contact cleaning solution tothe contacts with a pipe cleaner, cottontipped swab, orcomparable soft applicator.Unless specified otherwise in this service data, lubrication ofcontacts is not required.4. Do not defeat any plug/socket B+ voltage interlocks with whichinstruments covered by this service manual might be equipped.5. Do not apply AC power to this A/V Receiver and/or any of itselectrical assemblies unless all solid-state device heat sinks arecorrectly installed.6. Always connect test instrument ground lead to the appropriateground before connecting the test instrument positive lead. Alwaysremove the test instrument ground lead last.Insulation Checking ProcedureDisconnect the attachment plug from the AC outlet and turn thepower on. Connect an insulation resistance meter(500V) to theblades of the attachment plug. The insulation resistance betweeneach blade of the attachment plug and accessible conductive parts(Note 1) should be more than 1M-ohm.Note 1 : Accessible Conductive Parts including Metal panels, Inputterminals, Earphone jacks, etc.Electrostatically Sensitive (ES) DevicesSome semiconductor (solid state) devices can be damaged easily bystatic electricity. Such components commonly are calledElectrostatically Sensitive (ES) Devices. Examples of typical Esdevices are integrated circuits and some field effect transistors andsemiconductor chip components.The following techniques should be used to help reduce theincidence of component damage caused by static electricity.1. Immediately before handling any semiconductor component orsemiconductor-equipped assembly, drain off any electrostaticcharge on your body by touching a known earth ground.Alternatively, obtain and wear a commercially availabledischarging wrist strap device, which should be removed forpotential shock reasons prior to applying power to the unit undertest.2. After removing an electrical assembly equipped with ES devices,place the assembly on a conductive surface such as aluminumfoil, to prevent electrostatic charge buildup or exposure of theassembly.3. Use only a grounded-tip soldering iron to solder or unsolder ESdevices.4. Use only an antistatic solder removal device. Some solderremoval devices not classified a “anti-static” can generateelectrical charges sufficient to damage ES devices.5. Do not use freonpropelled chemicals. These can generateelectrical charge sufficient to damage ES devices.6. Do not remove a replacement ES device from its protectivepackage until immediately before you are ready to install it. (Mostreplacement ES devices are packaged with leads electricallyshorted together by conductive foam, aluminum foil, orcomparable conductive material).7. lmmediately before removing the protective material from theleads of a replacement ES device, touch the protective material tothe chassis or circuit assembly into which the device will beinstalled.Caution : Be sure no power is applied to the chassis or circuit, andobserve all other safety precautions.8. Minimize bodily motions when handing unpackaged replacementES devices. (Normally harmless motion such as the brushingtogether of your clothes fabric or the lifting of your foot from acarpeted floor can generate static electricity sufficient to damagean ES device.)