Apple IMAC Service Source - Page 159

No Power, No fan, no hard drive noise, and the screen is black.

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No Power No fan, no hard drive noise, and the screen is black. 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. 7. Using a voltmeter, check the voltage on the battery test point (see graphic below). If the reading is over 3.5 volts, go to the next step. If the reading is under 3.5 volts, replace the battery and test again. 8. Plug the unit in, but do NOT press the power button. Using a voltmeter, check the voltage from the test point marked "12VSLP" (see graphic above). You should get a reading of approximately 12 volts. If the reading is 12 volts, go to the next step. If you don't get a 12 volt reading, go to step 11. 9. Press the power switch on the computer. Using a voltmeter, check the voltage on the test point marked "12V" (see graphic above). You should get a reading of approximately 12 volts. If the reading is 12 volts, go to the next step. If you do not get a 12 volt reading, replace the main logic board. 10. Using a voltmeter, check the voltage on the test point marked "5V" (see graphic above). You should get a reading of approximately 5 volts. If the reading is 5 volts, go to the next step. If you do not get a 5 volt reading, replace the main logic board. 14 - iMac (USB 2.0) Troubleshooting No Power Symptom Charts

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14 -
iMac (USB 2.0) Troubleshooting
No Power Symptom Charts
No Power
No fan, no hard drive noise, and the screen is black.
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.
7.
Using a voltmeter, check the voltage on the battery test point (see graphic below). If the reading is over
3.5 volts, go to the next step. If the reading is under 3.5 volts, replace the battery and test again.
8.
Plug the unit in, but do
NOT
press the power button. Using a voltmeter, check the voltage from the test
point marked “12VSLP” (see graphic above). You should get a reading of approximately 12 volts. If the
reading is 12 volts, go to the next step. If you don’t get a 12 volt reading, go to step 11.
9.
Press the power switch on the computer. Using a voltmeter, check the voltage on the test point marked
“12V” (see graphic above). You should get a reading of approximately 12 volts. If the reading is 12
volts, go to the next step. If you do not get a 12 volt reading, replace the main logic board.
10.
Using a voltmeter, check the voltage on the test point marked “5V” (see graphic above). You should get
a reading of approximately 5 volts. If the reading is 5 volts, go to the next step. If you do not get a 5 volt
reading, replace the main logic board.