Apple Powerbank G4 manual PMU NMI and PMU Reset pads on logic board, Caps lock LED power check

PMU NMI and PMU Reset pads on logic board

In addition to the power-on button pads on the logic board, there are pads for PMU NMI and PMU reset. These buttons work when their pads are shorted together (with a tool like the head of a flat blade screwdriver). They are marked PMU NMI and PMU RESET. The pads are separated with a white horizontal line between the pads.

These pads are located about 1cm left of the back left corner of the optical drive.

Caps lock LED power check

There are situations when the system is giving indications that it is shut down (no hard drive access, screen is dark, no fan, and so on). However, the logic board may still be running. In this case, the logic board is drawing power and generating heat.

Warning: In this situation, if the computer is put in an enclosed environment like a carrying bag, the computer can overheat.

Check this situation by pressing the caps lock key. If the LED glows, the PMU is running on the logic board. After pressing the caps lock key and perhaps other methods of waking it up fails, hold the power button down for six seconds to force a shut down of the computer. Restart the system to check if it boots up normally.

10 - PowerBook G4 (17-inch) Troubleshooting General Information