iMac Shutdown

Off-Topic
#1

Has anyone else experienced this? iMac randomly shutsdown…

Starting in early Sept… it was shutting down 8 or 9 times a day.
I took it to Apple, they kept it for a few weeks, and said “Its, fine, no problems” (ie. they didn’t do anything)
It ran flawlessly for 15 days after that… and I thought “Hmmm… may it was a loose connector that they tightened”
Then on Oct 5th, it shut down 7 times, with the shortest up time being 13 minutes… but the 7th reboot of the day lasted until 7:30 this morning (Oct 9th)
Today so far it has shutdown 11 times with uptimes between 4 minutes and 3 hours.
I have scoured the console logs, and don’t see anything that jumps out . Apple provided a program to collect data for them, but the file is 50mg and they provided no way to DELIVER it to them.

The only difference between running it at home, and them running in the (laughable) “GENIUS” bar is external devices (all of which I detailed for them)
USB mouse, USB keyboard, USB external Drive, and two monitors via Thunderbolt Mini-Display adapters

This is a 27" 2010 iMac.

Websearch shows hundreds of similar issues, but none with a specific resolution.

#2

[quote=219482:@Dave S]Has anyone else experienced this? iMac randomly shutsdown…

Starting in early Sept… it was shutting down 8 or 9 times a day.
I took it to Apple, they kept it for a few weeks, and said “Its, fine, no problems” (ie. they didn’t do anything)
It ran flawlessly for 15 days after that… and I thought “Hmmm… may it was a loose connector that they tightened”
Then on Oct 5th, it shut down 7 times, with the shortest up time being 13 minutes… but the 7th reboot of the day lasted until 7:30 this morning (Oct 9th)
Today so far it has shutdown 11 times with uptimes between 4 minutes and 3 hours.
I have scoured the console logs, and don’t see anything that jumps out . Apple provided a program to collect data for them, but the file is 50mg and they provided no way to DELIVER it to them.

The only difference between running it at home, and them running in the (laughable) “GENIUS” bar is external devices (all of which I detailed for them)
USB mouse, USB keyboard, USB external Drive, and two monitors via Thunderbolt Mini-Display adapters

This is a 27" 2010 iMac.

Websearch shows hundreds of similar issues, but none with a specific resolution.[/quote]

You did mention that before, and dismissed any idea that could be due to a temporary dip in power.

I know San Diego’s electricity is of the best quality, but have you tried putting your machine on an UPS ?

Sherlock Holmes has been portrayed saying : " when you have eliminated the impossible, whatever remains, however improbable, must be the truth". Have you really eliminated the impossible yet ?

#3

Why does this feel like deja vu? Is this the same machine you mentioned some time ago?

#4

been so upset about this… I didn’t realize I had posted here about it already… sorry :slight_smile:
It is not brown-outs (or dips in power). No other electronic device besides this iMac is affected, and I have a MacPro, and two laptops running as well…

I would think also, were it to be a “dip”, then at the very least I would percieve a slight change in the lighting in the room at the same moment, and like I said, there is a laptop running right next to the iMac and it doesn’t even stutter.

Plus according to apple the minimum voltage is 100volts… that would be a 20% drop from normal (120v), and THAT would cause the lights to blink.

Apple seems to think this is unique to me, when in fact I have pointed them at posts on their own discussion boards.

Sorry for venting again I guess…

#5

Did they test it WITH those same set of items plugged in ?
Are those devices all bus powered ?
What if you disconnect them
They might have tested a setup that you aren’t running and your setup stresses some portion of the power management circuitry or better stresses the crap out of the video card trying to run two thunderbolt displays that causes this
I’d be more suspect of the video card trying to drive two external TB displays since it really would push it hard and may just overheat

That vintage card wasnt built to drive that many pixels I dont think

#6

I still think it’s the power supply within the machine.

#7

Dave,

if you can’t find any helpful log and power is ok, then I would do the following

  1. Reset SMC and maybe NVRAM
    https://support.apple.com/en-us/HT201295

  2. Disconnect your USB-Keyboard and see if shut down going on. May you could use another one.

  3. Boot your iMac from a external clean MacOS X and see what happens

If shut downs going on, I guess your iMac has a hardware failure.

#8

and try disconnecting the thunderbolt monitors

#9

Do not believe that because other devices, especially portable, are unaffected, this particular machine is not sensitive to power variations. Laptops have their internal uninterruptible power supply with the batteries. The Mac Pro with his extension possibilities probably has a largely oversized power supply meant to drive a tank.

Dip on voltage is not the only offender. Micro power cuts and power spikes can also affect sensitive equipment. All ailments usually cured by an UPS. Some start at less than $100 http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=UPS

As a former electronician, what you describe tells me your machine chokes like an asthmatic struggling for air. There could be only two reasons for that : either the outlet in the wall, or the circuitry within. Trying an UPS is the easiest debug available. Since Apple did pretty much nothing except maybe running it for a day or two and saw nothing on their ultra secure, ultra regulated power supply, it would make sense.

The alternative is to open the case and verify the internal power. Given the nightmarish construction (glass fixed with adhesive unlike previous magnetic hold) and the truly fragile guts of these machines, I would not venture trying that just yet, unless the patient was really in critical condition.

In the meantime, venting may help regulate your internal power :wink:

#10

Did they test it WITH those same set of items plugged in ?

  • Are those devices all bus powered ?
    all USB devices are connected to a powered hub

  • What if you disconnect them
    Then the computer doesn’t work, or barring that all the programs are unavailable (all on external drive)

  • They might have tested a setup that you aren’t running
    Heck they only booted the machine twice during the two weeks they had it (terminal command LAST REBOOT) and yeah even though I told them EXACTLY what I had, they didn’t even note it down.

  • better stresses the crap out of the video card trying to run two thunderbolt displays that causes this. I’d be more suspect of the video card trying to drive two external TB displays since it really would push it hard and may just overheat. That vintage card wasnt built to drive that many pixels I dont think
    Vintage?.. [Nvidia GeForce GTX 675MX) I realize “late 2012” is a LONG time ago, but this card is supposed to be able to drive 3 27" RETINA displays, and I have two 19" standard displays, plus it has been running those displays for 2.5 years already.

SMC and NVRAM have been reset dozens of times. Booted in safe-mode, logs seem to say little (at least to me)

Machine is very well vented… and all intakes, fans, etc have been cleaned, by both myself and by Apple.
And yeah… no way on this green Earth am I going to even entertain the thought of opening it up. I used to fixed Apple ][ and //e back in the day, but this is like the difference between a 1969 Mustang, and a 2016 Mustang

#11

I would not recommend opening that machine to work on it yourself under any circumstances. You could tell me there was a lost kitten in there about to suffocate and I’d still tell you to bring it to Apple. It’s the stuff nightmares are made of.

Having said that, that’s exactly what you should do. It’s the power supply.

#12

[quote=219505:@Kem Tekinay]I would not recommend opening that machine to work on it yourself under any circumstances. You could tell me there was a lost kitten in there about to suffocate and I’d still tell you to bring it to Apple. It’s the stuff nightmares are made of.

Having said that, that’s exactly what you should do. It’s the power supply.[/quote]
That is what I think too. but I can’t convince Apple of that (yet)

FYI… the 675MX card can [quote]*This model can simultaneously support two external displays up to 2560x1600 via Thunderbolt.[/quote] and mine are 1280x1024 only

#13

Vintage since you said

So I assumed it was 5 years old as thats what you wrote

I’d try it with those detached & remove “other factors” from the equation
Remove the external USB drive (which if its into a powered hub should be ok since its not drawing power from the machine)

#14

Opps… I DID say 2010 didn’t I?.. sorry… its a 2012 :slight_smile:
Right now I have removed the two external monitors… and the external drive.
Which limits me to email and internet… since all my projects are on the external drive.

#15

Years ago a 24" iMac had similar symptoms. It turned out to be a very fine crack in the motherboard. Consider having yours closely inspected.

Whatever the cause, best of luck finding it and an inexpensive solution!

#16

I agree with Michel. If it ran fine at Apple (and the number of reboots says nothing about how long it ran) then the supplied power seems the most likely culprid.

Power can vary massively, especially when the computer AND the peripherals are on basically one electricity connection and your Mac Pro on another. And no, you won’t see a “dip in the lighting” which is on another circuit, and it is too fast anyway.

To be honest you are not very logical in your hunt for the root cause. Dismissing/Ignoring solid arguments like Michel’s is puzzling.

#17

Simple test without UPS:

Take the battery out of the laptop
Put both laptop and iMac (without peripherals) on the same plug
If they go both down then it is the line supply

It is not 100% conclusive if just the iMac goes down as it draws more power, but is conclusive if both go down.

#18

Markus, I appreciate your support. I am a bit intrigued too on the insistence of Dave and Kem that it must be the internal power supply. It could very well be, but a random issue in a machine that is notoriously difficult to open looks like a challenge to any repairman. Translated in dollars, looks like a small fortune and a long intervention. It is like a doctor saying without any examination “you’re a little fatigue, let’s do open heart surgery”.

Debugging hardware should proceed just the same way as software : start with the easiest and work your way inward.

If I remember right, Dave changed outlet, so chances are it is not the wall connector.

What is the state of the power coming in ? From previous conversation, that hypothesis was never verified in any way, besides the very dubious fact that laptops and the Pro run fine. That is far from being scientific. I suggested using a simple controller ($5.00) to verify voltage when a shutdown occurs. It would not show micro power interruptions or transient spikes, but that would be a start. If it shows voltage below 100 volts, then the culprit is found.

If voltage is alright then it could be short power interruption, as occurs when an electric engine starts, typically a fridge or some other appliance like an electric mower, a blower, a drill, whatever. The same thing also creates a spike. Ideal combination.

Now what are the reasonable options ? Trying the UPS costs around $100 for a well sized one. Then all is required is to wait for another shutdown that may never come.

If the shutdown still occurs, then there is certainty it is an internal power issue, and with that in hand, means taking the machine once again to Apple, plead the case with persuasion, and hope they will corner the bug. Chances are for a 2012 machine AppleCare has run out, so I would be extremely surprised if the bill runs under $200. As a matter of fact, since shutdowns manifest at random and weeks apart, Apple will most probably simply replace the power supply and not think further. If it is something like what Frederick suggests, then might as well buy another Mac. A motherboard is no peanut.

Now, this looks like the proverbial joke about engineers leaning under the hood of the stalled car. http://funnydot.com/jokes/Three-Engineers-In-A-Car.html

It is not my machine, and I have dealt with enough proponents of alternative medicine to know better than contradict religious beliefs. Personally, I do not use a crystal ball or a pendulum to debug things. Just hard facts and logic.

#19

P.S. Did Apple say that THEY did a reboot? Otherwise it would be a crash.

Check the times in the log.

#20

It could well be the internal power supply, but that is an expensive repair. So I would want to exclude any cheap to fix cause first.

If the log said it rebooted twice during the time at Apple then I would ask what happened then. If it happened during the night then that is pretty indicative of a shutdown there too.