Sudden loss of power on 2010 27"iMac

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Hello to all,
I have a 2010 27" iMac that I inherited form my son. I'm not really a newbie Mac user. I'm probably more than just a casual user but not a "power" user.
I've been using this iMac for the past year and except for a few minor issues, I never had any major problems with it yet. Ever since the onset of Online Classes (I teach college kids) I needed to use it everyday. Almost 3 weeks ago I was attaching (switching around USB cables at the back) when it suddenly shut off. I mean it was like someone cut off power to the machine. I booted it up again and it started normally and nothing seemed amiss. Then more than a week after that, I was again switching USB cables at the back when it happened again "poof" no power. So I assumed that I may have inadvertently touched or moved a connection to the power or the machine may have automatically shut down b/c of the temperature. (I noticed it was very warm...not hot but very warm). I let it cool for about 10 mins and booted it up. Again the machine worked fine.
Then this morning while I was chatting w some of my students online, we were waiting for the others to log it. I wasn't doing anything "physical" to the machine. In fact I wasn't touching it or anything...it again went black...no power. Oh and I have just turned it on maybe 15 minutes before so the machine was relatively cool.
Can anyone give their insight? Thanks so much.
 

Cory Cooper

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Hello,

It sounds to me like there is either a short somewhere in the USB ports or the USB cables you are connecting, the power button is loose/failing, or the power supply is starting to fail. It could also be a thermal issue - you can check to make sure the vents are blocked/clogged with dust or foreign material. Canned air can be useful to clear those vents.

C
 
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Hi Cory Copper, thanks for taking the time to give some enlightenment. I'm currently waiting for the suction cups I ordered online to open up the iMac. Mind you, haha I'm just a newbie DIY-er and I feel that brushing the innards and the fans and giving the vents a blast of compressed air might help and is way within my capabilities. But checking for a shorted USB port or failing power supply will be kinda way above my head. I don't know if this is relevant but I noticed that when I press the power button OR even just waking it up from sleep takes around 5 secs. Now I don't know if it was like this already before but ever since we shifted to online classes and had to use it everyday, I did notice the 5 secs. So I don't know if this is normal or slow. Can a dying PRAM battery cause this too? I'm running High Sierra, 12Gb RAM (2Gbx2 + 4Gbx2). My son had this converted into a Fusion Drive (I suppose its a 260Gb SSD mated w/ a 700++Gb HDD). Again thanks man, awesome! :D
 

Cory Cooper

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No worries.

It could simply be that you noticed the slight delay, since you are using the iMac more. My 2009 iMac does take a couple of secs before you hear the chime after pressing the power button. But, that doesn't explain the USB/power off issue.

Just be very careful opening up the iMac, as internal components can easily be damaged without proper procedures and training/experience. PRAM batteries on iMac models around that time are located on the back of the logic board, which is a pretty involved replacement, and isn't recommended for end-users. I doubt that the PRAM battery would cause that issue, especially if you haven't had any issues with the time being incorrect if you unplug the iMac.

You can simply clear the vents externally with the canned air, before opening up the iMac.

I do believe those model iMacs may have had an Apple Repair Extension Program for Video Issues, which would have long since expired, but I am not completely sure that they did.

It sounds more like a power supply issue, or possibly a logic board issue.

Who did the hard drive conversion to a Fusion Drive?

You could also try a couple of resets:
-How to reset the SMC of your Mac
-Reset NVRAM or PRAM on your Mac

C
 

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