mayer, I think the reference here is to the manual. Sound slike the OP only has 1 LED working on the iMac. all that the 1 LED shows is that the computer is plugged in and that the PSU receives power. It does not validate that the PSU is working. I would suggest to measure the output of the PSU.
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mayer, I think the reference here is to the manual. Sounds like the OP only has 1 LED working on the iMac. All that the 1 LED shows is that the computer is plugged in and that the PSU receives power. It does not validate that the PSU is working. I would suggest to measure the output of the PSU.
== UPDATE ==
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Check some of the test points with a multimeter
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[image|464862]
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[image|464862|align=center]
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'''Pin 1''' Ground
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'''Pin 3''' 5V power for Hard Drive(s). Note: If present, the 12V power will come directly from the Power Supply to the Hard Drive thru the power harness cable.
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'''Pin 4''' Standby 12V power (permanent power coming from power supply and present as long as AC cable is connected, even if computer is off); corresponds to LED #1
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'''Pin 6''' Backlight Control pulse width modulated signal (from logic board to LED backlight board, to adjust the backlight level setting according to user setup)
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'''Pin 11''' 12V Run-Mode power to logic board (coming from power supply, present as long as system is on or asleep); corresponds to LED #2
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'''Pin 11''' 12V Run-Mode power to logic board (coming from power supply, present as long as system is on or asleep); corresponds to LED #2
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'''Pin12''' Power On Request signal (from logic board to power supply when power button is pressed)
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'''Pin 13''' Backlight Enable (signal from logic board to Backlight Controller
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board, to enable backlight
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"Press power button and Verify if system turns ON. You may alternately check for presence of a '''12V DC signal between pin 11 and pin 1''' of logic board when power button is pressed."
mayer, I think the reference here is to the manual. Sound slike the OP only has 1 LED working on the iMac. all that the 1 LED shows is that the computer is plugged in and that the PSU receives power. It does not validate that the PSU is working. I would suggest to measure the output of the PSU.
+
+
== UPDATE ==
+
Check some of the test points with a multimeter
+
[image|464862]
+
'''Pin 1''' Ground
+
'''Pin 3''' 5V power for Hard Drive(s). Note: If present, the 12V power will come directly from the Power Supply to the Hard Drive thru the power harness cable.
+
'''Pin 4''' Standby 12V power (permanent power coming from power supply and present as long as AC cable is connected, even if computer is off); corresponds to LED #1
+
'''Pin 6''' Backlight Control pulse width modulated signal (from logic board to LED backlight board, to adjust the backlight level setting according to user setup)
+
'''Pin 11''' 12V Run-Mode power to logic board (coming from power supply, present as long as system is on or asleep); corresponds to LED #2
+
'''Pin12''' Power On Request signal (from logic board to power supply when power button is pressed)
+
'''Pin 13''' Backlight Enable (signal from logic board to Backlight Controller
mayer, I think the reference here is to the manual. Sound slike the OP only has 1 LED working on the iMac. all that the 1 LED shows is that the computer is plugged in and that the PSU receives power. It does not validate that the PSU is working. I would suggest to measure the output of the PSU.