User Guide

Troubleshooting General/ Testing for Power - 5
Plug in the computer, but leave the iMac powered OFF. Ground the
black probe on the volt meter (by inserting it into the metal
chassis). With one hand behind your back, touch the red probe on
the volt meter to the positive lead of capacitor C28 on the logic
board (see the photograph on the next page) to see if you have +5V
on the logic board. A +5V reading on the logic board means the
power supply is providing the necessary trickle voltage to logic
board.
Testing for Power at the Logic Board