I moved my iMac from home into my office and it would not turn on at all there. So I took it around the corner to a repair man and it turned on straight away at his shop. He suggested I get a UPS to see if that makes a difference. So I took it back to my office and tried plugging it into a UPS, but it still did not work. The input / output voltage on the UPS display read 245 volts (I am in Australia where the wall sockets should be somewhere in the range of 230-240V). I figured that the voltage must be too high for the iMac, since the power at home (where it works fine) is 230-240V as it should be. So I unplugged the UPS from the wall to run off the battery and the UPS started outputting 230V yet still the iMac wont turn on!

There has to be something wrong with my office building because the iMac works fine everywhere else! Is there anything specific to the iMac power supply that could cause this?

  • Have you tested the socket in the office with a lamp or hair dryer etc? If not then you should...
    – Solar Mike
    Sep 14, 2019 at 12:47
  • The UPS was doing its job putting out the expected voltage when unplugged from the mains. The UPS should have reported bad wiring as well, such as reversed hot/neutral or a bad or non-existent ground. Have your employer employ an electrician to evaluate the electrical circuits in your office. I've seen more electrical equipment not work, or work poorly until they are damaged permanently but faulty wiring. Sometimes it can be as simple as a badly-wired socket, but sometimes it can be systemic.
    – IconDaemon
    Sep 14, 2019 at 13:18
  • I know it's not the focus of your question, but it is generally not advisable to unplug a UPS from the wall when turned on, especially powering equipment. It loses the ground which can cause various undesired effects.
    – samkass
    Sep 15, 2019 at 9:03
  • @SolarMike The socket works fine with every computer other than the iMac. And the same thing happens with every socket in the office building.
    – lionliam96
    Sep 15, 2019 at 11:10
  • @IconDaemon I`ve asked the real estate agent/body corporate to take a look at the problem but getting them to take it seriously is proving difficult...
    – lionliam96
    Sep 15, 2019 at 11:13

1 Answer 1


You can plug the Mac into any voltage from 100 - 240v & it will not care at all, so that's a red herring.

I'd suggest a mains socket tester plug, to ensure the socket is correctly wired, from the wall & also the UPS.
Also, skip the UPS & test the Mac directly in the wall too. That would be the most probable fail point.

  • I will see if I can pick one up and give it a go. I`ve directly tried a lot of sockets in this building and still none of them work for my iMac.
    – lionliam96
    Sep 15, 2019 at 11:16
  • Have you tried a different mains cable in the iMac, or checked the fuse? That seems the one static component.
    – Tetsujin
    Sep 15, 2019 at 13:31

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