IBM 1200 Hardware Maintenance Manual page 48

Note: An audible noise from the AC Adapter does not
always indicate a defect.
Checking operational charging
To check operational charging, use a discharged battery
pack (Battery ASM) or a Battery ASM that has less than
50% of the total power remaining when installed in the
computer.
Perform operational charging. If the battery status indicator
or icon does not turn on, remove the Battery ASM and let it
return to room temperature. Reinstall the Battery ASM. If
the charge indicator or icon still does not turn on, replace
the Battery ASM.
If the charge indicator still does not turn on, replace the
system board. Then reinstall the Battery ASM. If the
reinstalled Battery ASM is not charged, go to the next
section.
Checking the Battery ASM
Note: The Battery ASM may not be able to charge when it
is hot. In that case, remove it from the computer
and leave it at room temperature for a while. After it
cools down, reinstall it and recharge it.
Do the following:
1. Power off the computer.
2. Remove the battery pack and measure the voltage
between battery terminals 1 (-) and 7 (+). See the
following figure.
Terminal (NiMH)
1
2
3
4
38
ThinkPad i Series 1200/1300 HMM
4
3
2
1
Signal / Voltage (V dc)
Ground
BT-SENSE
Reserve
Reserve
7
6
5