PowerBook G4 (15-inch FW800) Troubleshooting - 7
General Information
PMU Reset pads on logic board
In addition to the power-on button pads on the logic board, there are pads for 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 RESET. The pads are separated with a white
horizontal line between the pads.
These pads are located near the edge of the logic board, just above center of the hard
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 blower, 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.