Modelo A1312 / Mediados de 2011 / Procesador Core i5 de 2.7 & 3.1 GHz o Core i7 de 3.4 GHz

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power supply unit terrible noise

iMac Intel 27" EMC 2429 2.7GHz


I have iMac27" with some problem on power supply unit.

The noise is terrible and unacceptable.

I open iMac and at the moment I have to try PSU stand alone to understand if is PSU problem or other boards connected to it.

Imac run correctly, power is correct but the noise is very terrible.

PSU is LITEON pn 614-0446 PA-2311-02A REV:B.

I need:

1. schematic pin out 16 pin connector

2. similar experiences in the world: it's very terrible to discover this terrible noise.


Contestado! View the answer Yo también tengo este problema

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Can you describe the noise is is a high pitched whine or squeal?


It's the same as mosquito giant but very very loud. I try to rebuild tht welding contact. Two days ago this appear a solution . Yesterday I was out of otffice but I left iMac in stop with 220Vac connected. This morning I switch on and the noise appear terrible too. I think is a problem of magnetostriction inside chokes. layout is terrible and temperature is quite high. i didn't connected nothing and iMac it's the same as I buy it from apple store. If I could connect PSU stand alone I could understand where is the problem. i need connection pin out but , believe, I don't find it in internet and I looked for a long time. Can you tell me something? If I buy a new PSU the problem, I think, should the same. I have to understand where is the problem and repair it. PSU unit run correctly but noise is impossible to hear.



Thats the 50kHz 220 volt European power line frequency you are herring.



have you solved the problem?

The Sound ist terrible!



Yes, I resolved.

I used some particular glue to encapsulate ferromagnetic devices.

The noise now is disappear.




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Solución Elegida

I would recommend just replacing the PSU not trying to fix your current unit.

Often when I get these squealers I end up replacing quite a few parts and end up wasting a lot of time. The transformers and the filtering capacitors often need replacing.

Unless you don't have the fixtures and proper tools to work on the it can be dangerous!

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Thank Dan

Don't worry for me: I'm a PSU designer. It's my bread. The problem is: is it possible to have pin out connector?



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ferrarogiuseppe estará eternamente agradecido.
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