LENOVO ThinkPad T420 - T420i – How to check the Battery – How to check the charger - password resets - Laptop repair and service

Category: Laptop Repair and Service 

Contents of this article 

• Power adapter checking procedure
• Battery pack checking procedure 
• Passwords Reset 

LENOVO ThinkPad T420 -T420i

Power system checkout
To verify a symptom, do the following:
1. Turn off the computer.
2. Remove the battery pack.
3. Connect the ac power adapter.
4. Check that power is supplied when you turn on the computer.
5. Turn off the computer.
6. Disconnect the ac power adapter and install the charged battery pack.
7. Check that the battery pack supplies power when you turn on the computer.

Checking the ac power adapter
You are here because the computer fails only when the ac power adapter is used.
• If the power problem occurs only when the docking station or the port replicator is used, replace the docking station or the port replicator.
• If the power-on indicator does not turn on, check the power cord of the ac power adapter for correct continuity and installation.
• If the computer does not charge during operation, go to “Checking operational charging” on page 35.
To check the ac power adapter, do the following:
1. Unplug the ac power adapter cable from the computer.
2. Measure the output voltage at the plug of the ac power adapter cable. See the following figure:

Note: Output voltage of pin no.2 of the ac power adapter may different from the one you are servicing.
3. If the voltage is not correct, replace the ac power adapter.
4. If the voltage is acceptable, do the following:
• Replace the system board.
Note: Noise from the ac power adapter does not always indicate a defect. Checking operational charging
To check whether the battery charges properly during operation, use a discharged battery pack or a battery pack that has less than 50% of the total power remaining when installed in the computer.

Perform operational charging. If the battery status indicator or icon does not turn on, remove the battery pack and let it return to room temperature. Reinstall the battery pack. If the charge indicator or icon still does not turn on, replace the battery pack.
If the charge indicator still does not turn on, replace the system board. Then reinstall the battery pack. If it is still not charged, go to the next section.
Checking the battery pack
Battery charging does not start until the Power Manager Battery Gauge shows that less than 96% of the total power remains; under this condition the battery pack can charge to 100% of its capacity. This protects the battery pack from being overcharged or from having a shortened life.
To check your battery, move your cursor to the Power Manager Battery Gauge icon in the icon tray of the Windows taskbar and wait for a moment (but do not click), and the percentage of battery power remaining is displayed. To get detailed information about the battery, double-click the Power Manager Battery Gauge icon.
Note: If the battery pack becomes hot, it may not be able to charge. Remove it from the computer and leave it at room temperature for a while. After it cools down, reinstall and recharge it.
To check the battery pack, do the following:
1. Power off the computer.
2. Remove the battery pack and measure the voltage between battery terminals 1 (+) and 7 (-). See the following figure:

3. If the voltage is less than +11.0 V dc, the battery pack has been discharged.
Note: Recharging will take at least 3 hours, even if the indicator does not turn on. If the voltage is still less than +11.0 V dc after recharging, replace the battery.
4. If the voltage is more than +11.0 V dc, measure the resistance between battery terminals 5 and 7.
The resistance must be 4 to 30 K Ω. If the resistance is not correct, replace the battery pack. If the resistance is correct, replace the system board.
Checking the backup battery
Do the following:
1. Power off the computer, and unplug the ac power adapter from it.
2. Turn the computer upside down.
3. Remove the battery pack
4. Remove the backup battery 

5. Measure the voltage of the backup battery. See the following figure.

• If the voltage is correct, replace the system board.
• If the voltage is not correct, replace the backup battery.
• If the backup battery discharges quickly after replacement, replace the system board.

Passwords

As many as three passwords may be needed for any ThinkPad Notebook: the power-on password (POP), the hard-disk password (HDP), and the supervisor password (SVP). If any of these passwords has been set, a prompt for it appears on the screen whenever the computer is turned on. The computer does not start until the password is entered.
Note: If only an SVP is installed, the password prompt does not appear when the operating system is booted. 

Power-on password
A power-on password (POP) protects the system from being powered on by an unauthorized person. The password must be entered before an operating system can be booted.

Hard-disk password
There are two hard-disk passwords (HDPs):
• User HDP—for the user
• Master HDP—for the system administrator, who can use it to get access to the hard disk even if the user
has changed the user HDP
Note: There are two modes for the HDP: User only and Master + User. The Master + User mode requires two HDPs; the system administrator enters both in the same operation. The system administrator then provides the user HDP to the system user.

Attention: If the user HDP has been forgotten, check whether a master HDP has been set. If it has, it can be used for access to the hard disk drive. If no master HDP is available, neither Lenovo nor Lenovo authorized service technicians provide any services to reset either the user or the master HDP, or to recover data from the hard disk drive. The hard disk drive can be replaced for a scheduled fee.
Supervisor password
A supervisor password (SVP) protects the system information stored in the ThinkPad Setup Utility. The user must enter the SVP in order to get access to the ThinkPad Setup Utility and change the system coniguration.
Attention: If the SVP has been forgotten and cannot be made available to the service technician, there is no service procedure to reset the password. The system board must be replaced for a scheduled fee.
How to remove the power-on password
To remove a POP that you have forgotten, do the following:
(A) If no SVP has been set:
1. Turn off the computer.
2. Remove the battery pack..
3. Remove the backup battery

4. Turn on the computer and wait until the POST ends. After the POST ends, the password prompt does not appear. The POP has been removed.
5. Reinstall the backup battery and the battery pack.
(B) If an SVP has been set and is known by the service technician:
1. Turn on the computer.
2. When the ThinkPad logo comes up, immediately press F1 to enter ThinkPad Setup. When the POP icon is appearing on the screen, enter the POP.
3. Select Security, using the cursor directional keys to move the menu.
4. Select Password.
5. Select Power-On Password.
6. Type the current SVP in the Enter Current Password ield. then leave the Enter New Password ield blank, and press Enter twice.
7. In the Changes have been saved window, press Enter.
8. Press F10; then, in the Setup conirmation window, select Yes.
How to remove the hard-disk password
To remove a user HDP that has been forgotten, when the SVP and the master HDP are known, do the following:
1. Turn on the computer.
2. When the ThinkPad logo comes up, immediately press F1 to enter ThinkPad Setup. When the POP icon is appearing on the screen, enter the POP.

3. Select Security, using the cursor directional keys to move the menu.
4. Select Password.
5. Select Hard-disk x password, where x is the letter of the hard disk drive. A pop-up window opens.
6. Select Master HDP.
7. Type the current master HDP in the Enter Current Password ield. then leave the Enter New Password field blank, and press Enter twice.
8. Press F10.
9. Select Yes in the Setup Coniguration window. Both user HDP and master HDP will have been removed.