Bon c'est galère la Knowledge Base : faut s'inscrire pour y accéder. Donc je te copie les 2 articles qui correspondent à ton problème
1) Article n° : 58385
Follow these steps to troubleshoot a PowerBook or iBook computer that will not turn on:
1. Disconnect any peripheral devices attached to the computer.
2. Remove AC adapter and battery from the PowerBook or iBook computer, and reset the power manager. For more information on resetting the power manager, refer to article 14449: "PowerBook and iBook: Resetting Power Manager."
3. Verify the outlet is working and all connections are tight. Connect the AC adapter to a known good power outlet and make sure power adapter cord is fully inserted into the power adapter. Make sure you are using the AC adapter that was designed for your computer. Refer to article 16168: "PowerBook and iBook: Battery, Recharger and AC Adapter Identification" for help identifying the appropriate power adapter.
4. Connect the AC adapter to the PowerBook or iBook computer, wait a few seconds, and then press the computer's Power button. If the computer turns on, it is likely that you have an unusable battery. If you have another battery you should try it. If you do not, have your computer serviced. If the computer did not turn on with the AC adapter connected, go to step 5.
5. Remove the AC adapter, insert a charged battery, and press the Power button again. If the computer turns on, you most likely have an unusable AC adapter. You should contact Apple for a replacement. If the computer does not turn on, proceed to step 6.
6. If the issue persists, it is likely that your computer has a hardware condition that requires a repair.
Note: The PowerBook G3 Series battery has a series of LEDs that indicate the charge level when you press the small button. If only one LED flashes, or no LEDs are on, the battery is depleted and needs to be charged.
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2) Article n° 14449
PowerBook and iBook: Resetting Power Manager
The Power Manager is an integrated circuit that is usually on the logic board of the PowerBook and iBook. As the name implies, it is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and I/O as far as looking at the serial port and modem so it does not sleep when connected.
Over time, the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. Examples would be not powering on, not waking from sleep, not charging the battery, or not seeing the AC Adapter, among others.
Resetting the Power Manager is accomplished in a variety of ways depending upon the computer. These methods are described below.
WARNING: Resetting the Power Manager on any PowerBook or iBook will permanently remove a RAM disk, if present, and all of its contents.
PowerBook G3 Series (M4753)
1. If the computer is on, turn it off.
2. Simultaneously press Shift-Fn (function)-Ctrl (control)-Power.
3. Wait 5 seconds.
4. Press the Power button to restart the PowerBook computer.
PowerBook G3 Series (Bronze Keyboard) (M5343)
1. If the computer is on, turn it off.
2. Press the reset button on the rear of the computer. The reset button is located between the external video and modem (RJ-11) ports.
3. Wait 5 seconds
4. Press the Power button to restart the PowerBook computer.
Note: When you reset the power manager, wait at least 5 seconds before pressing the power button to start up the computer. If you do not wait at least 5 seconds, the reset procedure may fail. (If you suspect that the reset procedure has failed, press the reset button again and wait 5 seconds before pressing the Power button.)
PowerBook (FireWire)
1. If the computer is on, turn it off.
2. Press the reset button located on the rear panel of the computer between the external video and modem ports.
3. Wait 5 seconds.
4. Press the Power button to restart the computer.
Note: Resetting the power manager also resets the Date and Time. After the reset, the system clock is set to 12:00 A.M., 01/01/1904.