ThinkPad T420 - Beep Symptoms; No-Beep Symptoms; LCD-Related Symptoms

Beepsymptoms
Table4.Beepsymptoms
Symptomorerror
FRUoraction,insequence
Onebeepandablank,unreadable,orashingLCD.1.ReseattheLCDconnector.
2.LCDassembly.
3.ExternalCRT.
4.Systemboard.
Onelongandtwoshortbeeps,andablankorunreadable
LCD.
1.Systemboard.
2.LCDassembly.
3.DIMM.
Twoshortbeepswitherrorcodes.
POSTerror.See“Numericerrorcodes”onpage47.
Twoshortbeepsandablankscreen.
1.Systemboard.
2.DIMM.
Twoormorebeeps,oracontinuousbeep.Operating
systemstartssuccessfully.
Ifamini-PCIEthernetcardisinstalled,conrmthatAlert
OnLAN2intheThinkPadSetupprogramisdisabled.
Threeshortbeeps,pause,threemoreshortbeeps,and
oneshortbeep.
Oneshortbeep,pause,threeshortbeeps,pause,three
moreshortbeeps,andoneshortbeep.
1.DIMM.
2.Systemboard.
Onlythecursorappears.
Reinstalltheoperatingsystem.
Fourcyclesoffourshortbeepsandablankscreen.
Systemboard(securitychip)
Fiveshortbeepsandablankscreen.
Systemboard
No-beepsymptoms
Table5.No-beepsymptoms
Symptomorerror
FRUoraction,insequence
Nobeep,power-onindicatoron,LCDblank,andno
POST.
1.Makesurethateveryconnectorisconnected
tightlyandcorrectly.
2.DIMM.
3.Systemboard.
Nobeep,power-onindicatoron,andLCDblankduring
POST.
1.ReseatDIMM.
2.Systemboard.
Thepower-onpasswordpromptappears.Apower-onpasswordorasupervisorpasswordisset.
TypethepasswordandpressEnter.
Thehard-diskpasswordpromptappears.Ahard-diskpasswordisset.Typethepasswordand
pressEnter.
LCD-relatedsymptoms
Important:TheTFTLCDforthenotebookcomputercontainsmanythin-lmtransistors(TFTs).Thepresenceofa
smallnumberofdotsthataremissing,discolored,oralwayslightedischaracteristicofTFTLCDtechnology,but
excessivepixelproblemscancauseviewingconcerns.
IftheLCDyouareservicinghastwoorlessvisibledefectivepixels,itshouldnotbeconsideredfaulty.However,ifthe
LCDhasthreeormorevisibledefectivepixels,itwillbedeemedasdefectivebyLenovoanditshouldbereplaced.
Notes:
•ThispolicyappliestoallThinkPadNotebookspurchasedon1January,2008orlater.
50ThinkPadT420andT420iHardwareMaintenanceManual
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