Lenovo 2808DKU, 28155YU, 28155XU Power system checkout, Checking the AC adapter, Pin Voltage V dc

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 52

v“Checking the battery pack” on page 52

v“Checking the backup battery” on page 53

Checking the AC adapter

You are here because the computer fails only when the AC adapter is used.

vIf the power problem occurs only when the docking station or the port replicator is used, replace the docking station or the port replicator.

vIf the power-on indicator does not turn on, check the power cord of the AC adapter for correct continuity and installation.

vIf the computer does not charge during operation, go to “Checking operational charging” on page 52.

To check the AC adapter, do the following:

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:

3

2

1

(20V)

Pin Voltage (V dc)

1+20

20

3Ground

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:

vReplace the system board.

vIf the problem persists, go to “FRU tests” on page 48.

Note: Noise from the AC adapter does not always indicate a defect.

General checkout 51