iMac 24" (early 2009) shuts down randomly

[JorgeVazquez]

Hi! I was reading this forum for years and now... i registered because a problem (ouch!) ... I wonder if someone can help....

My iMac shuts down randomly since i installed Yosemite. It always happen when i'm doing something, sometimes opening Safari, sometimes launching an App... the system doesn't shut down if you don't touch it. I made my investigations....

- I re-install Mavericks and Snow Leopard and the problem remains. So is not related with Yosemite at all.
- Apple Hardware Test (the long one) says there's no problem with any piece of hardware (the iMac didn't shuts down while performing the test).
- There's nothing plugged into the mac, so the problem is not related with peripherals.
- There's no pattern into the system log. The last messages recorded before the system shuts down are always different (no errors).
- The temperature registered in all sensors are fine, all the fans are working properly.
- I have an UPS unit so the current should be nice and protected.

So... Can all the shuts down be only fault of the Power Supply Unit? I can switch on the mac after the shut down without any problem. There's a way to test the PSU before i pay for a new one (expensive part!)? Any idea of something different causing all the trouble?

Thanks!!

 

[aicul]

Maybe a silly suggestion, but did you check that the power cable is well set on the iMac (not on the UPS).

 

[Bruno09]

Also, reset the SMC : http://support.apple.com/es-es/HT3964

 

[JorgeVazquez]

Maybe a silly suggestion, but did you check that the power cable is well set on the iMac (not on the UPS).

Yes, the cable is well set. I can switch on again without touching it.

----------

Also, reset the SMC : http://support.apple.com/es-es/HT3964

I did it, nothings change

 

[leitenperger]

you might want to take a look at this thread: https://discussions.apple.com/thread/3938355?start=0&tstart=0