IBM PS/2 N51 SX Hardware Maintenance Service page 23

5.5 Checking the Standby Battery
1. Invert the system unit and place it on its top.
2. Remove the battery pack from the system and remove the bottom cover.
3. Disconnect the battery connector from the voltage converter.
4. Plug the AC adapter into the system and power-on the system.
5. Measure the output voltage at the connector on the voltage converter.
PICTURE 7
+------------------------------------------------------------------------+
¦ Pin
+------------------------------------+-----------------------------------¦
¦ 1
+------------------------------------+-----------------------------------¦
¦ 3
+------------------------------------------------------------------------+
If the voltage is less than +4 V dc, replace the voltage
converter.
If the voltage is greater than +4 V dc, go to the next step.
6. Power-off the system.
7. Reconnect the standby battery to the voltage converter.
8. Power-on the system and leave it approximately 30 minutes to allow the
standby battery to be charged.
9. Power-off the system again and disconnect the standby battery.
10. Measure the voltage of the standby battery.
If the voltage is less than 3.5 V dc, replace the standby battery.
If the voltage is greater than 3.5 V dc, replace the voltage
converter.
IBM PS/2 Model N51 SX HMS
Checking the Standby Battery
¦ Voltage (V dc)
¦ +4
¦ Ground
¦ Copyright IBM Corp. 1991
5.5 - 1
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