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How to Reset PMU on a G4 PowerBook

Updated February 21, 2017

If your PowerBook G4 laptop is unable to wake up after being put in sleep mode or won't turn on after pushing the power button, the power management unit may have a problem, according to the official Apple website. The PMU handles the functionality of your computer's shut down and sleep functions and can also affect the computer's capability to hold a battery charge. Resetting the PMU should only be performed if you have attempted to troubleshoot sleep and charging issues with no success because resetting the computer's PMU restores the settings to their original configuration.

Exit out of all open applications, and press the "Power" button on the laptop. Click the "Shut Down" button on the pop-up menu.

Remove the power adaptor from the laptop's power port, and remove the battery from the bottom of the Powerbook. Hold down the "Power" button on your laptop for five seconds, and release it, according to the official Apple site.

Place the battery back into the laptop, and plug the power adaptor into the power port and into an electrical socket. Push the "Power" button to power on the laptop.

Exit out of all open applications, and press the "Power" button on the laptop. Click the "Shut Down" button on the pop-up menu.

Hold down the "Shift," "Control," "Option" and "Power" buttons simultaneously for five seconds, and release the keys.

Allow five seconds to pass, and press the "Power" button to turn on the computer. According to the official Apple site, the laptop's clock may be reset to 00:00 after the PMU is reset. To change the time, double-click the time and check the "Automatically Set Date/Time" box.

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