ThinkPad T420 - Power System Checkout; Checking the Ac Power Adapter; Checking Operational Charging

Powersystemcheckout
Toverifyasymptom,dothefollowing:
1.Turnoffthecomputer.
2.Removethebatterypack.
3.Connecttheacpoweradapter.
4.Checkthatpowerissuppliedwhenyouturnonthecomputer.
5.Turnoffthecomputer.
6.Disconnecttheacpoweradapterandinstallthechargedbatterypack.
7.Checkthatthebatterypacksuppliespowerwhenyouturnonthecomputer.
Ifyoususpectapowerproblem,seetheappropriateoneofthefollowingpowersupplycheckouts:
•“Checkingtheacpoweradapter”onpage37
•“Checkingoperationalcharging”onpage37
•“Checkingthebatterypack”onpage38
•“Checkingthebackupbattery”onpage38
Checkingtheacpoweradapter
Youareherebecausethecomputerfailsonlywhentheacpoweradapterisused.
•Ifthepowerproblemoccursonlywhenthedockingstationortheportreplicatorisused,replacethe
dockingstationortheportreplicator.
•Ifthepower-onindicatordoesnotturnon,checkthepowercordoftheacpoweradapterforcorrect
continuityandinstallation.
•Ifthecomputerdoesnotchargeduringoperation,goto“Checkingoperationalcharging”onpage37
.
Tochecktheacpoweradapter,dothefollowing:
1.Unplugtheacpoweradaptercablefromthecomputer.
2.Measuretheoutputvoltageattheplugoftheacpoweradaptercable.Seethefollowinggure:
Pin
Voltage(Vdc)
1+20
20
3
Ground
1
2
3
(20V)
Note:Outputvoltageacrosspin2oftheacpoweradaptermightdifferfromtheoneyouareservicing.
3.Ifthevoltageisnotcorrect,replacetheacpoweradapter.
4.Ifthevoltageisacceptable,dothefollowing:
•Replacethesystemboard.
•IftheproblempersistsandyoursystemsupportsthePCdoctorforDOS,goto“FRUtests”on
page33.
Note:Noisefromtheacpoweradapterdoesnotalwaysindicateadefect.
Checkingoperationalcharging
Tocheckwhetherthebatterychargesproperlyduringoperation,useadischargedbatterypackorabattery
packthathaslessthan50%ofthetotalpowerremainingwheninstalledinthecomputer.
Chapter3.Generalcheckout37
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