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Power system checkout
To verify a symptom, do the following:
1. Turn off the computer.
2. Remove the battery pack.
3. Connect the ac adapter.
4. Check 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. Check 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:
v “Checking the AC adapter”
v “Checking operational charging” on page 53
v “Checking the battery pack” on page 53
v “Checking the backup battery” on page 54
Checking the AC adapter
You are here because the computer fails only when the AC adapter is used.
v If the power problem occurs only when the docking station or the port replicator
is used, replace the docking station or the port replicator.
v If the power-on indicator does not turn on, check the power cord of the AC
adapter for correct continuity and installation.
v If the computer does not charge during operation, go to “Checking operational
charging” on page 53
To check the AC adapter, do the following:
1. Unplug the ACc adapter cable from the computer.
2. Measure the output voltage at the plug of the AC adapter cable. See the
following figure:
1
2
3
(20V)
Pin Voltage (V dc)
1 +20
20
3 Ground
Note: Output voltage of pin no.2 of the AC adapter may different 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:
v Replace the system board.
v If the problem persists, go to “FRU tests” on page 50.
Note: Noise from the AC adapter does not always indicate a defect.
52 ThinkPad T400 and R400 Hardware Maintenance Manual