PowerBook 100 through PowerBook 5300: Resetting Power Management Unit (PMU)

This document describes the PowerBook Power Manager and explains how to reset it. Resetting the power manager also resets the date and time. After the reset, on some PowerBooks, the system clock is set to 00:00 on 1 January 1904

This document refers to Apple products manufactured before November 1997. Click here for products manufactured after that date.

This article has been archived and is no longer updated by Apple.

Function

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.

Occasionally, over time, the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. Examples would be not turning on, not waking from sleep, not charging the battery, or not seeing the AC Adapter, among others.

A reset button is not intended for resolution of a stall or situation in which the computer is non-responsive. A reset should not be necessary except as a last resort in cases where a hardware failure of the power management system is suspected. Pressing the reset button resets the PowerBook hardware, including NVRAM, and forces the computer to shut down.

For most situations, a restart is sufficient. If the computer has stopped responding, only reset the computer if nothing else has resolved the situation. If this is the case, see below for instructions on locating the reset button or key combination for your model of PowerBook. If your computer is later than the models listed here, see technical document 14449, "PowerBook and iBook: Resetting Power Management Unit (PMU)".


Warning: Resetting the Power Manager on any PowerBook will permanently remove a RAM disk, if present, and all of its contents.

PowerBook models covered in this document

  1. PowerBook 100
  2. PowerBook 140, 145, 145 B and 170
  3. PowerBook 150
  4. PowerBook 160, 165, or 180
  5. PowerBook 500 series
  6. PowerBook 200 and 2300 Series
  7. PowerBook 190, 1400, 2400, 3400, and 5300 Series

 


PowerBook 100

    1. Remove the AC adapter and the battery.
    2. Flip the battery contact switch on the rear of the computer to the down position.
    3. Let the PowerBook sit without power connected for 3 to 5 minutes.
    4. Simultaneously press and hold the reset and interrupt buttons on the side of the computer for 15 seconds.
    5. Reinstall the battery, reconnect the AC adapter if necessary and flip the battery contact switch on the rear of the computer to the up position.

PowerBook 140, 145, 145 B and 170

    1. Remove the AC Adapter and the battery.
    2. Let the PowerBook sit without power connected for 3 to 5 minutes.
    3. Using two paper clips, simultaneously press and hold the reset and interrupt buttons for 5 to 10 seconds.
    4. Reinstall the battery and, if necessary, reconnect the AC adapter.

Note: Both recessed buttons (commonly known as the reset and interrupt buttons) are located next to the power button on the back panel of the PowerBook.

PowerBook 150

    1. Remove the power adapter and battery from PowerBook.
    2. Push the reset button in the back of the computer with a paper clip and hold for 5 to 10 seconds.
    3. Plug the AC adapter into the AC (wall) outlet.
    4. Reconnect the power adapter and push the reset button in back again, but just briefly. You should hear a small pop from the speaker; do not be concerned.
    5. Push main power button in back (large exposed button). The PowerBook should turn on.
    6. Apple suggests charging the battery for at least 8 hours before running on battery power.

If the PowerBook powers on, the battery may be reinserted. If it fails to start, the PowerBook may require service.

PowerBook 160, 165, or 180

    1. Remove the AC adapter and the battery.
    2. Let the PowerBook sit without power connected for 3 to 5 minutes.
    3. Reinstall the battery and, if necessary, reconnect the AC adapter.

Note: Steps 1 and 2 will usually reset the Power Manager. However, if the computer still exhibits the same issue, repeat steps 1 and 2 and then follow the step listed below before reinstalling the battery.

    1. Using two paper clips, simultaneously press and hold down the reset and interrupt buttons for 5 to 10 seconds. They are located next to the power button on the back panel of the PowerBook.

PowerBook 500 series

    1. Remove the AC adapter and the battery.
    2. Let the PowerBook sit without power connected for 3 to 5 minutes.
    3. Simultaneously press and hold Command-Option-Control-Power On for 5 to 10 seconds.
    4. Reinstall the battery and, if necessary, reconnect the AC adapter.

PowerBook 200 and 2300 Series

    1. Press and hold the power button on the rear of the 200 or 2300 series computer for 30 to 45 seconds.*
    2. (see Caution) If resetting the Power Manager chip does not resolve the situation, reset the code for the Power Manager chip by removing all power sources and letting the computer sit for 10 minutes. (Disconnect the AC adapter, remove the battery and the internal backup battery.) This forces the PowerBook Duo to reload the Power Manager code from the system software.


**Caution** Apple-authorized service technicians may remove the internal back up battery to reset the Power Manager. If you are not an Apple-authorized service technician, please note that removing the internal backup battery is not a simple procedure and is not recommended. If anything is damaged in your attempt to remove the battery, it will not be covered under warranty.

PowerBook 190, 1400, 2400, 3400, and 5300 Series
The PowerBook 190, 1400, 3400, and 5300 Series have two different ways to reset the Power Manager. The only difference is the location of the reset button. See the table below for the location of the reset button on each PowerBook series.

PowerBook Reset Button Location (on rear of computer)
190 Series Below the video-out port
1400 Series Between the ADB and Serial ports
2400 Series Above the floppy drive connector
3400 Series Left of the Serial port
5300 Series Below the video-out port



Resetting the Power Manager


    1. If the computer is on, turn it off.
    2. Restart the computer by holding down the reset button for 10 to 20 seconds. (See chart above for location of the reset button for your PowerBook series.)
    3. If the computer does not restart, repeat step 2 three or four times.

Resetting the Power Manager and PRAM
Resetting the parameter RAM (PRAM) when the computer is shut down also resets Power Manager. The following process resets both the Power Manager and the parameter RAM.


    1. If the computer is on, turn it off.
    2. Make sure the Caps Lock key is not down.
    3. Restart the computer. Immediately after hearing the startup sound, simultaneously press and hold Command-Option-P-R. (If you do not hold down the key combination within 5 to 10 seconds after the computer restarts, you must repeat steps 1-3.)
    4. Hold down the keys until you hear the startup sound again. Then release the keys.
    5. If the computer shuts itself off, press the reset button on the back of the computer to turn it back on. (See chart above for location of the reset button for your PowerBook series.)
    6. When the computer has finished starting up, restore any custom settings for the desktop pattern, memory, network, AppleTalk, trackpad, power conservation, and so forth.

For additional information, please see the following article:

14449 PowerBook and iBook: Resetting Power Management Unit (PMU)

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