21
General checkout
Power system checkout
To verify a symptom, follow the steps below:
1. Turn off the computer.
2. Remove the battery pack.
3. Connect the AC adapter.
4. Make sure that power is supplied when you turn on the computer.
5. Turn off the computer.
6. Disconnect the AC adapter and install the charged battery pack.
7. Make sure that the battery pack supplies power when you turn on the
computer.
If you suspect a power problem, see the appropriate one of the following power
supply checkouts:
• “Checking the AC adapter” on page 21
• “Checking operational charging” on page 21
• “Checking the battery pack” on page 22
Checking the AC adapter
You are here because the computer fails only when the AC adapter is used.
• If the power-on indicator does not turn on, check the power cord of the AC
adapter for correct continuity and installation.
• If the computer does not charge during operation, go to “Checking
operational charging”.
To check the AC adapter, follow the steps below:
1. Unplug the AC adapter cable from the computer.
2. Measure the output voltage at the plug of the AC adapter cable. See the
following figure:
1
2
Voltage (V DC)
+20
0
Pin
1
2
Note:
Output voltage for the AC adapter pin No. 2 may differ from the one you
are servicing.
3. If the voltage is not correct, replace the AC adapter.
4. If the voltage is acceptable, do the following:
• Replace the system board.
• If the problem persists, go to “Lenovo U31-70” on page 26.
Note:
Noise from the AC 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.
