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Aktuelle Version von: Ben ,

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I have a similar problem with my mid 2010 i5 - 2,8GHz - 27inch iMac. It does not power up. I checked the 4 LEDs. When I disconnect the power cable on the back and then put it back on one (!) LED is lighting up once (!) and then goes off again and shortly afterwards lights up a second time but then no LED is lighting up and the power button does not do anything. I can't see which LED it is because the board is still in the housing but I suspect it beeing the first one. In the technician's manual it sais that LED 1 should light up steadily if connected to power. What could it mean if the LED just lights up twice shortly?
 
EDIT: I just measured the pins on the logic board according to the technical document. I have 12V between pin 1 and 4 and i have constantly about 3V between pin 1 and 12. So, when pressing the power ON button pin 12 is not changing - it is the same when pressed and when not pressed. I then have nothing on pin 11, where the button is pressed or not pressed at all.
EDIT: I just measured the pins on the logic board according to the technical document. I have 12V between pin 1 and 4 and i have constantly about 3V between pin 1 and 12. So, when pressing the power ON button pin 12 is not changing - it is the same when pressed and when not pressed. I then have nothing on pin 11, where the button is pressed or not pressed at all.
 
I am a bit confused because 12V on pin 4 should also make LED 1 light up constantly, which is not the case. And even if I disconnect the power button from the logic board I still have 3V on pin 12.
 
=== Update (12/27/2017) ===
 
I swapped out the logicboard and this solved it.

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Bearbeitet von: Ben ,

Text:

I have a similar problem with my mid 2010 i5 - 2,8GHz - 27inch iMac. It does not power up. I checked the 4 LEDs. When I disconnect the power cable on the back and then put it back on one (!) LED is lighting up once (!) and then goes off again and shortly afterwards lights up a second time but then no LED is lighting up and the power button does not do anything. I can't see which LED it is because the board is still in the housing but I suspect it beeing the first one. In the technician's manual it sais that LED 1 should light up steadily if connected to power. What could it mean if the LED just lights up twice shortly?
 
EDIT: I just measured the pins on the logic board according to the technical document. I have 12V between pin 1 and 4 and i have constantly about 3V between pin 1 and 12. So, when pressing the power ON button pin 12 is not changing - it is the same when pressed and when not pressed. I then have nothing on pin 11, where the button is pressed or not pressed at all.
 
I am a bit confused because 12V on pin 4 should also make LED 1 light up constantly, which is not the case. And even if I disconnect the power button from the logic board I still have 3V on pin 12.

Status:

open

Ursprünglicher Beitrag von: Ben ,

Text:

I have a similar problem with my mid 2010 i5 - 2,8GHz - 27inch iMac. It does not power up. I checked the 4 LEDs. When I disconnect the power cable on the back and then put it back on one (!) LED is lighting up once (!) and then goes off again and shortly afterwards lights up a second time but then no LED is lighting up and the power button does not do anything. I can't see which LED it is because the board is still in the housing but I suspect it beeing the first one. In the technician's manual it sais that LED 1 should light up steadily if connected to power. What could it mean if the LED just lights up twice shortly?

Status:

open