Our 3 year old imac intermittently powers off of its own accord. Won’t restart unless unplugged. Sometimes then stays up for days, other times just for seconds. Software up-to-date etc.

Any recommendations or do I go to the Genius bar ?

Thanks

Genius Bar, failing that fix it yourself

https://www.ifixit.com/Device/iMac

With the right tools they are quite easy to work on.

Where did you buy it from? If Apple they’ll repair it for free. So I’d probably go for the Genius Bar.

John Lewis. Started playing up just after the 2 year warranty expired.

Jam bo, thanks for the link. May try to replace the power supply…

John Lewis. Started playing up just after the 2 year warranty expired.

How old is it now? Might be worth a call to John Lewis,there’s often a free year extra guarantee on electricals. 5 years for tellys!

Try resetting the SMC first:

https://support.apple.com/en-gb/HT201295

Edit: and PRAM/NVRAM:
https://support.apple.com/en-gb/HT204063

There’s some kind of six year european warranty on electricals. John Lewis I reckon would honour it. http://forums.moneysavingexpert.com/showthread.php?t=1719963

If you’ve applied it to your scrotum all I can advise is warm water followed by lots of E45. Not sure you’ll ever repair it though.