User Guide

Troubleshooting General/ Power Flow - 3
Power Flow
Power is controlled in the iMac system by the power supply
board. Once the unit is plugged in, power flows from the AC outlet
at the wall to the AC inlet on the power supply board. From there,
the power flows through the power filter board and on to the
analog/video board, the logic board, and all its attached
components.
Click here
to view an animation of how power flows through the
iMac.
Power Supply Board Fuse
There is a fuse on the AC line on the power supply board (at
F901) that can be replaced if the computer has no power. (Refer
to the “No Power” symptom for a full troubleshooting scenario.)
Before replacing the fuse, you should do a continuity test with an
ohm meter. If the ohm meter registers “0”, the fuse is good. If
the meter registers “infinite,” the fuse should be replaced.
Refer to “Testing for Power” later in this chapter for
instructions on how to check the power supply board fuse. Refer to
“Logic Board” in the Take Apart chapter to locate the fuse on the
power supply board.