My Mac Won’t Switch On!

May 12, 2011, By Christian Cawley

Macs are great. They look good, sound fantastic and generally give you a better computing experience than a traditional tower PC.

However unlike a tower PC there is little you can do to resolve any hardware-related issues that might occur. If your Mac refuses to switch on and you’ve tried all of the following suggestions, your best bet is to box up your computer and head straight for the nearest Apple Store for advice from one of the on duty Geniuses.

What to do if your Mac won't switch on

So, to the suggestions; this is a generalised list of steps that you should take when your Apple Mac mini, iMac or Mac Pro refuses to boot up. Not all steps are available on all devices, so read carefully so that you know which instruction applies to which computer…

Is it the Mac or the Cable?

The first thing you should do if your Apple Mac mini, iMac or Mac Pro won’t boo is to try the power cable in a different mains electrical outlet, swap for a different lead (from another item of domestic electrical hardware) and also check the fuse if you’re in the UK.

Failing this, in the case of the Mac Mini or a Mac Pro, confirm that the problem isn’t with the external display as opposed to the Mac itself.  You might do this by adjusting and reseating the cables or trying a different display unit.

Often problems on the Mac are caused by cabling not sitting correctly, so it might be worth spending a few minutes powering everything down and checking that all cabling is correctly inserted.

System Management Controller

If you have seen the phrase SMC floating around in relation to Macs, this is the abbreviation for System Management Controller.

This can be reset without the need for a display, and this is a great way to get your Mac operating again. (Note that on PowerPC Macs this controller is known as the Power Management Unit.)

On an Intel Mac that will not power up, you can reset the SMC by switching off the computer , disconnecting the power cord, waiting for 15 seconds, re-attaching the cord and pressing the power button to restart the computer.

Meanwhile on a Power PC Mac, you will need to know where the PMU is found on the motherboard. This differs depending on whether your computer is a G3, G4 or G5, so you will need to check at apple.com for the location of this small motherboard-based button. To reset the PMU, ensure your Mac is powered off, disconnect all cables, and then move to a carpet-free area with your Mac in a suitable position for the case to be opened safely. You will need to remove any jewellery and follow the usual safety precautions for opening your Mac (specific to the model you are using).

Locate the PMU and press the button, firmly, once before waiting 10 seconds and replacing the case cover and cables. After restarting your Mac, you should find it powers up and everything is back to normal!

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