Troubleshooting Resetting the PMU on the Logic Board - 10
Resetting the PMU on the Logic Board Resetting the PMU (Power Management Unit) on the logic board
can resolve many system problems. Whenever you have a unit that
fails to power up, you should follow this procedure before
replacing any modules.
1. Disconnect the power cord and check the battery in the bat-
tery holder (BT1). The battery should read 3.3 to 3.7 volts.
If the battery is bad, replace the battery, wait ten seconds,
and then reset the PMU (refer to the next step). If the bat-
tery is good, go to the next step.
2. Press the PMU reset switch (S1) once on the logic board and
then proceed to step 3. Do
NOT
press the PMU reset switch a
second time because it could crash the PMU chip.
3. WAIT ten seconds before connecting the power cord and pow-
ering the computer on. If the computer powers on, go to the
next step. If the computer does not power on, there is some-
thing else wrong with the computer, refer to the symptom/
cure chart, “No Power” in this chapter.
4. Run MacTest Pro and return the computer to the customer.
Note:
This entire procedure resets the computer’s PRAM. Be sure
to reset the computer’s time, date and other system parameter
settings before returning the computer to the customer.