Apple emac ati usb2 2005 サービスマニュアル
18 -
eMac ATI Graphics/USB 2.0/2005 Troubleshooting
General Information
Logic Board Battery
Important:
Apple highly recommends removing the battery when handling the logic board. Make
sure to use proper ESD protection when handling modules.
The battery on the logic board controls the stored system settings, such as date and time. It is
only necessary to test the battery when you can’t power on the computer, or the date and time are
reset every time the AC power is removed.
only necessary to test the battery when you can’t power on the computer, or the date and time are
reset every time the AC power is removed.
The battery is also used to power the PMU chip (because the PMU chip keeps time and must
always be running) when the computer is unplugged from the wall (AC power). The PMU is
always be running) when the computer is unplugged from the wall (AC power). The PMU is
very
sensitive and touching any circuitry that is connected to the PMU can cause it to crash. If the
PMU crashes, the battery life goes from about five years to about two days if the PMU is not
reset. Once the battery goes dead, the PMU will reset the time and date every time the AC power is
removed. To fix this situation, replace the battery and reset the PMU (refer to “How to Reset the
PMU on the Logic Board” mentioned earlier in this chapter).
PMU crashes, the battery life goes from about five years to about two days if the PMU is not
reset. Once the battery goes dead, the PMU will reset the time and date every time the AC power is
removed. To fix this situation, replace the battery and reset the PMU (refer to “How to Reset the
PMU on the Logic Board” mentioned earlier in this chapter).