ThinkPad T420 - Retaining Serial Numbers

•Torquedriver
Ifyouhaveatorquedriver,refertotheT orquecolumninthescrewinformationtableforeachstep.
•Makesurethatyouusethecorrectscrew.Itisrecommendedtousenewscrewsforreplacements.If
youhaveatorquescrewdriver,tightenallscrewsrmlytothetorquespeciedinthescrewinformation
tableforeachstep.
•Ensuretorquescrewdriversarecalibratedcorrectlyfollowingcountryspecications.
Retainingserialnumbers
Thissectionincludesthefollowingdescriptions:
•“Restoringtheserialnumberofthesystemunit”onpage62
•“RetainingtheUUID”onpage63
•“ReadingorwritingtheECAinformation”onpage63
Restoringtheserialnumberofthesystemunit
Whenthecomputerwasmanufactured,theEEPROMonthesystemboardwasloadedwiththeserial
numbersofthesystemandallmajorcomponents.Thesenumbersneedtoremainthesamethroughout
thelifeofthecomputer.
Ifyoureplacethesystemboard,youmustrestoretheserialnumberofthesystemunittoitsoriginalvalue.
Beforereplacingthesystemboard,savetheoriginalserialnumberbydoingthefollowing:
1.InstalltheLENOVOThinkPadHardwareMaintenanceDisketteVersion1.76orlater,andrestartthe
computer.
2.Fromthemainmenu,select1.SetSystemIdentication.
3.Select2.ReadS/NdatafromEEPROM.
Theserialnumberofeachdeviceinyourcomputerisdisplayed;theserialnumberofthesystemunitis
listedasfollows:
•20:Serialnumber
Writedownthatnumber.
Note:Theserialnumberofthesystemunitisalsowrittenonthelabelattachedtothebottomofthecomputer.
Afteryouhavereplacedthesystemboard,restoretheserialnumberbydoingthefollowing:
1.InstalltheLENOVOThinkPadHardwareMaintenanceDisketteVersion1.76orlaterandrestartthe
computer.
2.Fromthemainmenu,select1.SetSystemIdentication.
3.Select1.AddS/NdatafromEEPROM.Followtheinstructionsonthescreen.
IftheMTMandProductIDnumbersdifferfromeachotherontherearlabel,usewhatisshownforthe
ProductIDeld.Seeexamplebelow:
62ThinkPadT420andT420iHardwareMaintenanceManual
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