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4. Measure the voltage of the backup battery. See the
following figure.
Note: Be careful not to measure the wrong side of
the backup battery.
If the voltage is correct, replace the system board.
If the voltage is not correct, the backup battery has
been discharged. Replace the backup battery.
If the backup battery discharges quickly after
replacement, replace the system board.
Wire Voltage (V dc)
Red +2.5 to +3.7
Black Ground
Port Replicator Checkout
Use the following procedure to isolate a port replicator
problem. A port replicator attaches to the system
expansion connector at the bottom of the computer.
1. Power off the computer.
2. Remove the failing devices from the replicator.
3. Unplug the AC adapter from the replicator, if
attached.
4. Remove the port replicator from the computer.
5. Reconnect the failing device directly to the computer.
(If another device already connected to the computer,
remove it first.)
6. Go to “How to Run the Diagnostics” on page 212 and
follow that procedure.
7. If the advanced diagnostic device test does not find
an error, suspect a problem with the port replicator of
the system expansion bus.
8. Power off the computer and reconnect the port
replicator.
9. Power on the computer and run the following
advanced diagnostic tests:
Serial port test with the wrap plug installed on
the replicator
196 IBM Mobile Systems - ThinkPad HMM Volume 3