Specifications

No Power
The computer will not power on.
1. Verify the power outlet is good. Plug a different device into the socket to ensure there is power, or plug
computer into another outlet.
2. Check the power cord. Use a known good power cord.
3. Check connection of the power cord on both ends. Verify that the plug is securely plugged into both the
A/C outlet and back of the computer.
4. Remove keyboard, mouse, and other peripherals such as speakers.
5. Disconnect the power cord, place the computer in the service stand, and remove the user access plate.
6. Reset PMU. Refer to “Resetting the PMU on the Logic Board” mentioned earlier in this chapter or Kbase
article 95165.
7. Verify the battery is good before replacing modules. A drained battery may be indicative of a crashed
Power Management Unit. Does the battery measure at least +3.5v? If not, replace the battery and reset
the PMU. If the battery does measure over +3.5v, reinstall the battery and reset the PMU.
8. Connect the diagnostic cables (part 076-0897) between the upper housing components and the logic
board. Refer to “Service Cables” mentioned earlier in this chapter. Important: Diagnostic service cables
allow the unit to run while the bottom housing is open (as shown above). However, the computer cannot
run for more than five minutes with the bottom housing open. If it is open longer, the CPU may overheat
and become damaged.
9. Check the connection of the video cable on the LCD flat panel, and try to power on the unit again.
10. Check the AC line filter. To measure power at the AC line filter cable, disconnect the AC line filter cable
from the power supply cable. Switch your multimeter to read AC voltage. Touch the black probe to the pin
of the brown wire, and touch the red probe to the pin of the blue wire (see graphic below). Do you
measure 120v (line voltage)? If yes, go on to step 11. If no, replace the AC Line Filter.
No Power Symptom Charts
iMac (Flat Panel) Troubleshooting - 15