ThinkPad T420s - Page 70

180degreesmore
(Cross-section)
•Ifyouhaveatorquedriver,refertotheTorquecolumninthescrewinformationtableforeachstep.
•Makesurethatyouusethecorrectscrew.Itisrecommendedtousenewscrewsforreplacements.If
youhaveatorquescrewdriver,tightenallscrewsfirmlytothetorquespecifiedinthescrewinformation
tableforeachstep.
•Ensuretorquescrewdriversarecalibratedcorrectlyfollowingcountryspecifications.
Retainingserialnumbers
Thissectionincludesthefollowingdescriptions:
•“Restoringtheserialnumberofthesystemunit”onpage64
•“RetainingtheUUID”onpage65
•“ReadingorwritingtheECAinformation”onpage65
Restoringtheserialnumberofthesystemunit
Whenthecomputerwasmanufactured,theEEPROMonthesystemboardwasloadedwiththeserial
numbersofthesystemandallmajorcomponents.Thesenumbersneedtoremainthesamethroughout
thelifeofthecomputer.
Ifyoureplacethesystemboard,youmustrestoretheserialnumberofthesystemunittoitsoriginalvalue.
Beforereplacingthesystemboard,savetheoriginalserialnumberbydoingthefollowing:
1.InstalltheLENOVOThinkPadHardwareMaintenanceDisketteVersion1.76orlater,andrestartthe
computer.
2.Fromthemainmenu,select1.SetSystemIdentification.
3.Select2.ReadS/NdatafromEEPROM.
Theserialnumberofeachdeviceinyourcomputerisdisplayed;theserialnumberofthesystemunitis
listedasfollows:
•20:Serialnumber
Writedownthatnumber.
Note:Theserialnumberofthesystemunitisalsowrittenonthelabelattachedtothebottomofthecomputer.
Afteryouhavereplacedthesystemboard,restoretheserialnumberbydoingthefollowing:
1.InstalltheLENOVOThinkPadHardwareMaintenanceDisketteVersion1.76orlaterandrestartthe
computer.
2.Fromthemainmenu,select1.SetSystemIdentification.
3.Select1.AddS/NdatafromEEPROM.Followtheinstructionsonthescreen.
IftheMTMandProductIDnumbersdifferfromeachotherontherearlabel,usewhatisshownforthe
ProductIDfield.Seeexamplebelow:
64HardwareMaintenanceManual