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.

AC Line Filter

11. Check power supply output. Disconnect the diagnostic power cable from the power supply connector, and measure power at the power supply connector by touching the black probe to the ground pin, and using the red probe to measure power at the pins indicated in thegraphic below. Did you measure +12v at each point? If yes, continue with the next step. If no, replace the power supply.

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