IBM ThinkPad 340 Series Hardware Maintenance Manual page 337

Wire
Red
Black
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.
Checking the Standby Battery
1. Power-off the computer and unplug the AC Adapter
from the computer.
2. Open the keyboard, and remove the battery pack and
the diskette drive.
3. Remove the standby battery. (Refer to "2100 Standby
Battery and Front IR" on page 363 to remove the
battery.)
4. Measure the voltage of the standby battery.
If the voltage between red and black is 3.5 V dc
or greater, the voltage is correct. Go to Step 10
on page 328 to verify standby battery operation.
If the voltage is less than 3.5 V dc, go to the
next step.
5. Plug the AC Adapter into the computer and power-on
the computer.
6. Measure the output voltage at the connector on the
system board.
Voltage (V dc)
+2.5 to +3.7
Ground
ThinkPad 755CD, 755CDV (9545)
327