IBM ThinkPad X20 Hardware Maintenance Manual page 42

2. Turn the computer upside down.
3. Remove the backup battery (see "1030 Backup battery"
on page 59).
4. Measure the voltage of the backup battery. See the
following figure.
Red(+)
Wire
Red
Black
a. If the voltage is correct, replace the system board.
b. If the voltage is not correct, replace the backup
battery.
c. If the backup battery discharges quickly after
replacement, replace the system board.
38
ThinkPad X20, X21, X22, X23
Blac k(-)
@
Voltage (V dc)
+2.5 to +3.2
Ground