No Power

In a "No Power" situation, the system is completely dead. There is no LED, no hard drive power, and the screen is completely black. (Refer to "Testing for Power" earlier in this chapter for instructions on how to test for power at each component referenced in this procedure.)

Possible Cause

Possible Fix

Bad power cord, connection, or outlet.

  • Verify the power outlet is good.
  • Try a known-good power cord to determine if the existing power cord could be the problem. Make sure the power cord is connected securely at both ends.

Improperly aligned front power-on button

-If the front power-on LED is not centered properly within the inner button, the inner power button can become stuck between the LED and the inner bezel resulting in a no power, intermittent shut down, or sleep situation. Refer the LED Alignment procedure in the Adjustments chapter or to TIL article 58622 for steps to resolve the LED alignment issue.

Bad USB keyboard.

  • Verify the keyboard cable is connected properly to the computer.
  • Disconnect the keyboard and power on the system via the button on the front of the computer. Do you have power to the system now?

Yes: The keyboard is bad. Replace the keyboard. No: Go to next step.

The PMU chip needs to be reset.

  • Press the PMU chip on the logic board with the AC power cord disconnected. (See "The PMU Chip" and "Resetting the PMU on the Logic Board" mentioned earlier in this chapter.)
  • Connect the power cord and power on the system again.

Do you have power to the system now?

Yes: Test the unit with MacTest Pro and return the computer to the customer.

No: With the AC power cord connected, reset the PMU chip again. Do you have power to the system now? Yes: The battery is likely bad, check the battery. No: Go to the next step.

In a "No Power" situation, the system is completely dead. There is no LED, no hard drive power, and the screen is completely black. (Refer to "Testing for Power" earlier in this chapter for instructions on how to test for power at each component referenced in this procedure.)

Possible Cause

Possible Fix

Bad power/analog/video board

-Verify the fuse at F901 on the power/analog board is good. (Refer to "Testing for Power at the Power/ Analog Board Fuse" mentioned earlier in this chapter.) Did you get a "0" reading?

Yes: Check/reseat all power/analog/video board cable connections. Make sure the video board is securely attached to the CRT neck. If the No Power problem persists, go on to the next step.

No: Replace the power/analog/video board.

Bad power/analog/video board

- Check for trickle power on the logic board (Refer to "Testing J9 for +5 V Trickle Power on the Logic Board" mentioned earlier in this chapter). Trickle power is present as soon as the power cord is plugged into the computer.

Did you measure +5 V trickle power on pin 1 of connector J9? Yes: Go to the next step. No: Replace the power/analog/video board.

Bad down converter board

- Check for DCO voltage at location C10 on the logic board (Refer to "Testing DCO (Down Converter On) Voltage at C10 on the Logic Board") mentioned earlier in this chapter). Did you measure approximately -1.2 volts?

Yes: Go on to the next step.

No: Replace the down converter board.

Bad LED Power Switch Board

- Replace the LED/power switch board (922-4160). If that doesn't solve the problem, go on to the next step.

Bad CRT

- Replace the CRT.

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