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Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

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iMac won't power on, no LEDs blinking

Hi there,

our 2428 iMac had some strange behaviour until it got worse:

Some day, after disconnecting the power cord (after shutting down), the mac didn't turn on again. No fans spinning, nothing.

Leaving it disconnected for ~24h would helped and it started.

Any apple authorized service worker couldn't help / identify the problem.

Also a buzzing sound appeared (don't know if this one is maybe related to the power-on-problem).

Now, after disconnecting the device again after months of using, it won't power on - even after waiting those 24h...I opened the imac to look at the diagnostic leds, connected the power cord and tried to power on several times...none of the four leds were blinking. I also tried another power cord and the SMC reset. It did not help ):.

1. I removed the whole display, i.e. I removed all cables connected to the display (could this also led to the diagnostic leds not working?)

If I move really close to the psu, I can hear two clicking sounds is louder than the other.

2. What more could I try to diagnose the problem? (Maybe I missed something?)

3. Could the coin cell or any other part be the problem?

4. Also, I have a question about the psu apple part number. It's the ADP-200DFB. What's the difference to the 661-5299 or 614-0444 which I can buy here on ifixit?

5. And finally, why are those parts so expensive? I mean >130$ for a psu? It's nothing special, is it?

Thank you very, very much :)

Kind regards

Answered! View the answer I have this problem too

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Jacob, yes it does sound like a bad PSU. The clicking could be relays etc. just a guess until you can closer identify the location on the board. most likely not as simple as a battery issue. The cost for any items are based on quality and support. Yes you can get cheaper ones but do you get the same level of support etc.No such thing as a "crappy psu". After all, you are now feeling the results of a failed PSU.

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Hi, thanks for the tip. Because of your and my assumption I really hoped it's the psu and so I bought a used one from ebay. After carefully installation LED 1 began to light up and the imac is now fully functional (again) ;-).

Also the buzzing noise is gone.


Uhm, how can I mark this question as solved/answered?


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Jacob will be eternally grateful.
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