Mac Rebooting By Itself but no error message

[Peakoverload]

This has happened a couple of times in the past, within the past 18 months, but has now happened today twice. Unfortunately I've never been in the room when it has happened so I don't know what is happening.

I tend to leave my iMac on all the time and it's not set to sleep, just to turn the display off after 1hr. This morning I went to use it and found that it was on the login screen despite the fact that I never log out and had used it last night before going to bed and had left it on the desktop. When I logged in all the programs that I had left running last night re-launched.

After using the computer I left it on with a couple of programs running and left the room. A few minutes ago I heard it restart again and sure enough it was back at the login screen and when I logged back in the programs I had left running where launched again.

Whenever this happens I never get the usual "Your computer restarted because of a problem" error message, there are no messages at all.

Where on a Mac is the system log so I can see if anything caused the reboots? Has anyone experienced this, know what the cause might be?

 

[chscag]

The logs are located here: /Library/Logs/DiagnosticReports

Note that the Library mentioned above is NOT your user library.

Sudden restarts are usually caused by hardware but can also be software related. The usual culprits are: bad memory, power supply, and hard drive errors.

 

[Randy B. Singer]

Has anyone experienced this, know what the cause might be?

Usually when I've seen this it is either due to a failing power supply, cold solder joints around the power supply, or power fluctuations. If the latter is the problem (common this time of year due to everyone using their air conditioning), a good UPS that includes AVR is the solution.

Here is a personal experience. A law office was having a problem with their Macs shutting off unexpectedly, usually all at the same time. After some sleuthing, I found that the problem was that they had a refrigerator on the floor in the break room that, when it cycled on, it caused such a sag in power in the office that their Macs just shut off. (Sometimes a large laser printer will cause the same thing to happen when you turn it on.)

New CyberPower UPS's on each of the affected Macs solved the problem:

CyberPower 1000AVR ($105 with free shipping)
https://www.amazon.com/dp/B000QZ3UG0/?tag=macforums0e4-20
or
http://is.gd/iaxI4

 

[pm-r]

New CyberPower UPS's on each of the affected Macs solved the problem:

Wouldn't some of the alternative and cheaper UPS units work for such a situation?:

http://tinyurl.com/ycdvu324






- Patrick
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[Slydude]

I'll let Randy speak more directly to that point. I can tell you that I've purchased one or two of the surge suppressor type units that are supposed to provide the same function and found them to be useless for that after a very short time. The unit I had was cheaper than the device Randy recommended but really wasn't worth the money. At the time the UPS units I was seeing we're almost double the price of the CyberPower units.

 

[pm-r]

I was just really referring to the true UPS units and not the surge suppressor type units.

The APC® Back-UPS brand units are very popular in this area and often below the $100.00cdn mark

Tripp-lite used to be another excellent brand up here but a bit more money.






- Patrick
======






- Patrick
======

 

[Randy B. Singer]

Wouldn't some of the alternative and cheaper UPS units work for such a situation?:

No, not at all. It is absolutely critical that one's UPS has AVR (automatic voltage regulation). Otherwise your UPS won't handle sags in the power, and those sags are very harmful to a computer. (Especially to your hard drive.) Just about all UPS's in the $100 and under range don't have AVR.

In fact, before using the CyberPower units in the law office story I related, I purchased APC units (APC is sort of the General Motors of UPS's), and they didn't fix the problem. It turned out that they didn't include AVR. I returned them all.

The CyberPower unit that I recommended is actually a really good value. It's an excellent unit with a bunch of really nice features for the price.

I don't recommend APC units anymore because they no longer include AVR in many of their consumer-class models, even those that go for more than $100.

 

[harryb2448]

Don't go for a cheapie under say $100.00. This is the one I like and use.


https://www.amazon.com/dp/B00LEFYISA/?tag=macforums0e4-20

 

[pm-r]

No, not at all. It is absolutely critical that one's UPS has AVR (automatic voltage regulation). Otherwise your UPS won't handle sags in the power, and those sags are very harmful to a computer. (Especially to your hard drive.) Just about all UPS's in the $100 and under range don't have AVR.

Thanks Randy and that was also my understanding except for the price range quoted.

I don't think I've ever seen a locally advertised true UPS that didn't have Automatic Voltage Regulation (AVR) or Power Conditioning or whatever term they were using, but it's been nice for many to get some good ones on sale for under the $100.00cdn range, and I'm not including the units that ONLY do some sort of surge protection. And I will admit that one has to check the actual specs of the unit one is possibly purchasing.






- Patrick
======

 

[Randy B. Singer]

Don't go for a cheapie under say $100.00.

CyberPower offers a model selection tool here:
https://www.cyberpowersystems.com/tools/ups-selector/

It's important to remember that one should never attach a printer or scanner to a UPS's battery backup outlets because they have too much of a draw and you only need enough battery backup time to enable you to save your work and shut your computer down normally.

 

[Charmie91752]

Usually when I've seen this it is either due to a failing power supply, cold solder joints around the power supply, or power fluctuations. If the latter is the problem (common this time of year due to everyone using their air conditioning), a good UPS that includes AVR is the solution.

Here is a personal experience. A law office was having a problem with their Macs shutting off unexpectedly, usually all at the same time. After some sleuthing, I found that the problem was that they had a refrigerator on the floor in the break room that, when it cycled on, it caused such a sag in power in the office that their Macs just shut off. (Sometimes a large laser printer will cause the same thing to happen when you turn it on.)

New CyberPower UPS's on each of the affected Macs solved the problem:

CyberPower 1000AVR ($105 with free shipping)
https://www.amazon.com/dp/B000QZ3UG0/?tag=macforums0e4-20
or
http://is.gd/iaxI4

Yeah, power outage will do it. Especially if you have it set to reboot after an outage.

 

[Charmie91752]

I used to have one, and when a storm blew the lights out, it was great. But when the battery finally went dead, my Mac kept rebooting!