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80CHARCROFT
Findingalternativestoobsolete
passivesissimplyamatterof
discoveringtheirprevious
identities,asCharcroft’s
DebbieRowlandexplains.
Passivesarerarelythestarcomponentin
anycircuit,buttheydohavesomethingin
commonwiththeHollywoodgreats:their
tendencytobeknownunderdifferentnames.Just
asJohnWaynewasbornMarionMorrisonandthe
rapper50CentwaschristenedCurtisJackson,so
capacitorsandresistorstendtoadoptnewpart
numbersastheyareacquiredbydifferent
manufacturers.
Unlikesemiconductors,whichareeither
proprietaryparts,orattachdifferentprefixesto
agenericpartnumbertodenotedifferent
manufacturers,passivestakeamorefreestyle
approachtonomenclature.Asinglepassive
can,therefore,beknownunderarangeofvery
differentpartnumbers.Whilstthismayinitially
makethebuyers’lifemorecomplicateditalso
meansthat,whenfacedwithanobsolete
passive,thereisagreaterchanceoffindinga
readilyavailablealternativedisguisedundera
differentpartnumber.
Take,forexample,thestandard100nF,50V,10%
tolerance,radialmouldedmulti-layerceramic
capacitor(MLCC).Thiscanbeorderedbymilitary
drawingnumberMIL-C11015/18,orunderarange
ofdifferentreleaseandcommercialpartnumbers
dependingonthemanufacturer.Forexample,the
Syfer8123Z0500104KXandVishayCK05BX104K
arebothobsolete,butcanbereplacedasadirect
The passive
alternativebyanyoftheotherpartsnumbers.To
widenthescopestillfurtheritispossibletousea
partwithatightertoleranceof5%simplyby
changingtheKtoJorchangingthesuffixofthe
formerly
MIL-Specpartnumber.
Thehistoryofpassivecomponentmanufacturers
known as…..
0
8 islitteredwithbuy-outsandacquisitions,many
ofwhichresultinthesamecomponentsbeing
B
E
R
givennewpartnumbers.Themostrecent
exampleisKemet’sacquisitionofArcotronicsin
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O
V
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M
December2007andtheannouncementofthe forRoHS-compliantparts,whilstotherssimplychangedtheexistingpartstobe
saleoftheirwettantalumbusinessinSeptember RoHScompliantandissuednewpartnumbersforthelegacy,non-RoHSparts.
P
E
2008.Forlong-lifetimeproductssuchasmilitary
R
O
andaerospaceequipment,thiscanmeanthat Withmanymanufacturersfacingtoughchoicesbetweenproducinghigh-volume
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U
buyerscanbefacedwithbillsofmaterialsfor parts,orsupportinglow-volumeapplicationssuchasaerospace,smaller
maintenancerepairandoverhaul(MRO)which manufacturerscanoftenprovideanalternative.Forexample,theUK-based
C
N
G
stillreferencemanufacturerswhodisappeared specialistpassivesdistributorandmanufacturer,CharcroftElectronics,acquired
U
R
overtwentyyearsago,butwhosepassiveslive Oxley’ssilvermicabusinessandalsonowmanufacturesTTelectronics,Welwyn
S
O
S
onunderanewmanufacturerandpartnumber. Components’4800seriesprecisionresistors,savingbothfromprobable
obsolescence.Fortunatelyforbuyers,althoughtheseproductsarebranded
N
I
C
RoHShasalsoaddeditsowncomplexityto Charcroft,theymaintaintheiroriginalpartnumbers.
R
O
passivepartnumbers:somemanufacturers
havechosentocreatenewpartnumbers > www.charcroft.com
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