4SafetyPrecautions
4.1General Guidelines
1. Whenservicing,observe the original leaddress.If ashortcircuit isfound,replace all partswhich have been
overheated ordamaged by theshort circuit.
2. Afterservicing,seetoitthatallthe protective devicessuch as insulation barriers,insulation papersshields are
properlyinstalled.
3. Afterservicing,make the following leakagecurrentchecks topreventthecustomerfrombeing exposed toshock
hazards.
(This“SafetyPrecaution”isapplied onlyinU.S.A.)
1. Beforeservicing,unplug thepowercordtopreventan electricshock.
2. Whenreplacing parts,useonlymanufacturer’srecommendedcomponentsforsafety.
3. Check thecondition ofthe powercord.Replaceifwearordamage isevident.
4. Afterservicing,be suretorestorethelead dress,insulation barriers, insulation papers,shields, etc.
5. Beforereturningthe serviced equipmenttothe customer,be suretomakethe following insulation resistancetest
topreventthe customerfrombeing exposedtoashock hazard.
4.1.1LeakageCurrentColdCheck
1. Unplugthe AC cordand connectajumperbetween the twoprongson the plug.
2. Measurethe resistancevalue,withan ohmmeter,between thejumpered AC plug and each exposed metallic
cabinetpart on the equipmentsuchasscrewheads,connectors,controlshafts,etc.When the exposedmetallic
parthas areturnpathtothechassis,the readingshouldbebetween1M and 5.2M .
Whenthe exposed metaldoes nothaveareturnpathtothe chassis,the reading mustbe .
Fig.1
4.1.2LeakageCurrentHotCheck(See Figure1)
1. Plug the AC corddirectlyintothe AC outlet.Donotusean isolation transformerforthischeck.
2. Connecta1.5k ,10wattsresistor, inparallel witha0.15µFcapacitor,between eachexposed metallicpartonthe
setand agood earthground suchasawaterpipe,as showninFigure1.
3. UseanAC voltmeter,with1000 ohms/voltormoresensitivity,tomeasurethepotentialacrossthe resistor.
4. Check each exposed metallicpart,and measurethe voltage ateachpoint.
5. Reversethe AC plug inthe AC outletandrepeat each ofthe above measurements.
6. The potentialat any pointshouldnotexceed0.75 voltsRMS.Aleakage currenttester (Simpson Model229or
equivalent)maybeused tomake thehot checks,leakagecurrentmustnotexceed 1/2milliamp.Incasea
measurementisoutofthe limitsspecified,thereisapossibilityof ashock hazard,and the equipmentshouldbe
repaired and rechecked beforeit isreturned tothecustomer.
4.1.3Cautionforfuse replacement
