The symptoms you describe could occur on a Macintosh PowerBook 190, 1400, 3400, or 5300 series computer. The situation you describe is often caused by a corruption of the power manager controller on the logic board or corrupted Parameter RAM (PRAM) which can cause it to restart continually like this. It has been successfully resolved in some cases by one of the following three procedures:
*** WARNING ***** WARNING ***** WARNING ***** WARNING ***
All of the following Power Manager Reset procedures for all of the Macintosh PowerBook computers will permanently remove a RAM disk, if present, and all of its contents. Resetting the Parameter RAM will reset some settings you have selected for networking other services back to the factory defaults.
*** WARNING ***** WARNING ***** WARNING ***** WARNING ***
Reset the Parameter RAM (PRAM)
Reset the Parameter RAM (PRAM) from shutdown state. Resetting the Parameter RAM (PRAM) when the computer is shut down also resets the power manager.
1. Unplug the AC adapter.
2. Power on the computer while it is running from the battery only.
3. Immediately after you press the power key, hold down Option, Command (Apple), P, and R.
4. Keep holding down these four keys until you have heard the startup chime at least one additional time after the initial startup chime*. (If your PowerBook computer emits multiple chimes when you are holding down the Option-Command-P-R keys, skip to Step 7.) Unlike other PowerBook models, often these PowerBook computers will be only emit a single startup chime. Then the screen goes dark/blank and the green sleep light stays on solid (not blinking on and off like it does when the computer is in Sleep mode).
5. Press the Reset button (on the back of the PowerBook) one more time and the PowerBook starts up after a brief pause. Note: If the PowerBook powers off and the sleep display light stays a solid green - no blinking, press the reset button once.
6. If the PowerBook does not turn on from the Reset button, turn the PowerBook on by pressing the Power-On key in the upper right corner of the keyboard.
7. After the computer has started up select Shut Down from the Special menu.
8. Plug in the AC adapter. If the computer remains shutdown, you will know that you have successfully reset the PRAM and power manager and your computer should now function normally. If the computer powers on when you plug in the AC adapter, you need to reset the power manager.
Reset The Power Manager
1. Remove the battery.
2. Disconnect the AC Adapter from the PowerBook and unplug it from the wall outlet.
3. Press and hold the Reset button for one minute. The Reset button is located behind the port access door on the back of the unit below the video connector.
4. Plug the AC Adapter into the wall outlet.
5. Plug the AC Adapter into the PowerBook. It should now behave normally when you choose Shut Down from the Special menu. If it does not, then continue with step 6.
6. If the computer powers on when you plug in the AC adapter, you need to bring your computer to an authorized Apple dealer, or call Apple Support to check on your service options.
Have the Backup Battery Removed
Have an authorized Apple Service technician remove all power from the computer for approximately 15 minutes.
1. Remove the main battery(ies) and AC Adapter.
2. Disconnect the backup battery.
3. Wait 15 minutes and then retest for original Issue.
Important note: Removal of the backup battery should only be done by an authorized Apple service provider because the backup battery is not a user-accessible part. Be advised that if an end user attempts to perform this procedure and in the process damages any components, any damage incurred will not be covered under warranty. If you do not have access to a local service provider, you can call Apple Support to have your PowerBook computer sent in for repair at the Apple Service Center.
This article was published in Information Alley on 11 March 1997.