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I have a new desktop computer (Lenovo M81) that shutdowns unexpectedly. Other times, it is mouse and keyboard that become unresponding. If I put the computer to sleep and awake it, everything returns to normal.

I sent the computer to a certified technician, but he found nothing (computer wasn't shutting down for him) and simply replaced the PSU for prevention, but it didn't corrected the problem. It doesn't seem to be CPU, memory, overheating related. I even reinstalled the computer without success.

My last assumption would be that the shutdown is caused by current fluctuations. Is that possible? Can such problems also have repercussion on USB peripherals like keyboard and mouse? How can I be sure it is the source of the problem? Before spending 100$ for a UPS, I want to be sure it would correct my problem. What do you think?

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current doesn't fluctuate on its own. Only two things can alter the current: change in line voltage ( problem with the utility ) or a change in impedance ( the computer is trying to draw more or less power ). –  psusi Mar 8 '12 at 2:05
"Change of impedance" is meaningless in this context. –  Daniel R Hicks Mar 8 '12 at 2:11
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6 Answers

up vote 2 down vote accepted

The Lenovo M81s have a big problem with mainboard. We delivered to our customer about 60 PCs and 30 of it have a failuer with the mainboard. Lenovo Germany know the problem. Call Lenovo for support. They should change the mainboard.

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A little late to comment on this, but it was a problem with the motherboard. They changed it and all problems are now gone. –  Charles Brunet Feb 17 '13 at 2:30
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No matter what, you should have your computer plugged into some sort of surge protector. With that being said, your typical surge protector will be effective for about 2-3 years. It is not often practiced, but recommended to replace the surge protector after that time. A UPS will often be effective for 4-6 years when protecting against surges.

You will also want to look into the different kind of UPS devices. There are three different types. So when picking the UPS, it's best to know what your environment is to effectively match. Beware of surges/spikes and brownouts.

Standby UPS Systems

These provide basic power protection in the form of battery backup plus surge protection. They do not, however, provide protection against brownouts.

Line–interactive UPS Systems

These are the next step up from standby UPS systems. Line–interactive systems feature Automative Voltage Regulation (AVR), which corrects power fluctuations. If the UPS detects a brownout, it draws on its battery to boost power. If it detects a surge, the UPS automatically trims power. This assures that connected equipment receives properly regulated power at all times.

Online UPS Systems

These provide the highest level of power protection. They convert incoming AC power to DC, then convert it back to clean, regulated AC. This process removes most power imperfections.

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+1 for the clean explanation about kinds of UPS. –  Charles Brunet Mar 8 '12 at 2:33
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How did you come to the conclusion that it's current related? I think it's maybe possible, but there's many, many other reasons this could be happening. You should check the event log to see what's going on as a first port of call. I assume you're using Windows :)

Control Panel > Administrative Tools > Event Viewer

In this past this kind of stuff used to be caused by bad capacitors too. Maybe you just have a faulty motherboard, since that wasn't swapped out. If it's new, I assume you also have a warranty on it for replacement of the whole thing. I'd do that tbh.

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Yes, but if it was the motherboard, how do you explain it wasn't shutting down when the technician looked at it? –  Charles Brunet Mar 8 '12 at 2:38
True, I missed that! What's the humidity like where the computer is situated? –  Chris Dennett Mar 8 '12 at 3:10
Dry. 30 to 35 % –  Charles Brunet Mar 8 '12 at 3:27
Maybe it's a humidity problem? Usually server farms are kept at a higher humidity to avoid problems (45%-65%). I'm not sure how much it affects modern computers. –  Chris Dennett Mar 8 '12 at 13:53
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A drop in voltage or "brownout" could certainly cause your computer to hang up or shut off. It could be as brief as a second or two. A UPS is probably going to be your solution. A small one can be had for $40. It won't keep you running for long in case of an actual power outage, but it should be more than sufficient to cover brief voltage fluctuations.

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You would have to purchase the correct type of UPS though. Some do not protect against brownouts whereas all protect against spikes. –  kobaltz Mar 8 '12 at 1:28
@kobaltz, no, all UPSes protect against brownouts -- that is kind of the point. –  psusi Mar 8 '12 at 2:02
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A UPS is always a good idea, and I recommend APC and don't just buy a cheap one. I don't know if power fluctuations could affect the function of your keyboard however if you have a PSU that where "intelligent" I suppose it could shutdown your system if it were unable to correct or compensate for the faulty power. A good electrician could asses your power quality but I would be more inclined there is something going on with your system.

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Do you have any indication that the power where your computer is installed is somehow unstable? Do lights flicker sometimes or does the power go off frequently? Are there electric streetcars going down the street near you? Is the house old (before, say, 1960) with "doubtful" wiring?

Have you simply tried the computer in a different outlet? (Sometimes the outlet makes a poor connection.)

If there is no indication of "suspicious" power then I'd be highly doubtful that the problem is related to power.

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Yes, the house is old. I don't know how it is wired. It is possible other tenants are connected to the same circuits. I don't have clear indications that the problem is related to current, but I have no other ideas of what it could be... –  Charles Brunet Mar 8 '12 at 2:37
Try running on a different circuit, in a different part of the house. –  Daniel R Hicks Mar 8 '12 at 17:01
Chepest power analyzers cost around 100€, best around 10000... I would tend to think that old house was not built with computers in mind. You can have each wire (coming from fuse) to handle 1000W (iron)- 3 to 4 computers. –  ZaB Mar 9 '12 at 10:21
@ZaB -- Not much in the way of wiring is required to handle modern desktop computers. It's best to have a grounded outlet, but that's not a strong requirement. The power supplies in desktop computers have been quite robust and tolerant of power problems since the old IBM PC-1, which kind of set the standard for PC power supply design. (And since then the power demand of PCs has gone down to where current demand is not an issue.) It takes a fairly severe "glitch" or a complete loss of power for more than about 1/4 second to get through the power supply. –  Daniel R Hicks Mar 9 '12 at 12:41
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