Random Rebooting?


My brother and I put together a new computer this summer (this is my 2nd build) and recently we've been having problems with random reboots. This is what I know about the problem so far:

1) It's not due to a windows STOP error (I've deselected the "auto-reboot" Startup and Recovery option)
2) No RAM errors showed up during a 1.5 hour memtest (is this long enough?)
3) The frequency of the reboots is fairly low (about once or twice a week)
4) As far as we can tell, the reboots don't occur if someone's not on the computer (I've left up documents and they are always there when I get back)
5) The reboots don't seem to have any connection to power load - I can run 3dMark all the way through with no problems, but then I'll be typing a Word document and it will cut out.
6) These are always reboots, not shutdowns - this makes me unsure if this could be a power supply problem (wouldn't an unstable supply cause a shutdown?)
7) I disconnected the reset button from the motherboard to eliminate the possibility of a faulty button.
8) Heat doesn't seem to be an issue, since all the temps look stable and I've cleaned out the inside of the case.
9) The problem "may" have started after a thunderstorm during which the computer lost power. It was behind a surge protector, however, so I'm not sure what the probability is that the power supply got damaged or if that's even a possible cause.

Anyone have any ideas? I suppose the next step is to replace the power supply, but I'm not sure if a bad supply would cause these symptoms - if the voltages were unstable, I would think that the reboots would be more frequent in demanding applications (i.e. 3dMark). The fact that the reboots are completely unpredictable and leave no error message (at least not one that I can find) makes the problem incredibly frustrating. Does anyone have any guesses for the cause of the problem?
Hey, hey Chris!

Long time no see... OK, here's what I see:

Most important clue: It's not a BSOD. That's important. It means it's not for a device that Windows has drivers for, which rules out everything except Mobo, Memory, and PSU.

Is this by any chance the PSU that came with that case?
I had the same exact thing with my own first custom build, I thought it was the mobo, had it relaced, and realized it was the PSU. 1.5 hours is *generally* enough for memtest, but I'd say keep it running overnight.

Faulty PSU is prolly the case, and it's prolly not overheating nor over-consumption, it's just throwing a hissy-fit... and generally speaking it's not by heavy load but the switching on and off of different sectors that causes the reboots. Get yourself a brand name, it doesn't have to be expensive, but it just has to be something reliable.... even CompUSA brand is good, check it out if you have a CompUSA near you....
Hey CG, thanks for helping me again! The supply is actually a Thermaltake one that I had been using without problems for a year in my other computer - still, given that there seems to be a connection between the lightning storms and the reboots, I would probably point the finger there too.

What do you mean by the "switching on and off" of different "sectors" causing the reboots? As an electrical engineering major, I like to understand this stuff :grinning:

I'll take a look at CompUSA - from their website, the prices seem much higher than NewEgg's, but I'm not sure if I'll have time to order a new supply online before heading back to school (this is for my folks' computer).
I'm not an electric engineering major, so I'm probably wrong, but anyway, the way I see it is like this:

The PSU supplies several different voltages and currents (the different colored wires and connectors). The mobo and it's BIOS take care of the power state. Switching between the different levels (for instance S1 and S3) activates/deactivates different wires.

The OS turns on and off different components via the low-level driver interfaces. With cheap or dying mobos, the problem isn't with the output, but with the components in the PSU tiring out.

I'm not 100% on how the intestines of the PSU work, but AFAIK, it uses electomagnetism to switch between the coils used in the up/down transformer between the different voltages on the fly. So as it changes, if there is a single magnet or coil in the wrong place, even if only millimeters off, it can cause a problem....

The way it was in my PSU, when it went into suspend mode, and the OS attempted to send a wake up signal via a certain PCI device or onboard component, at that point under certain circumstances (temperature ranges, uptime values, etc.) the PSU fails and reboots.

I dunno, that was just my tuppence... you're the expert, you tell me :huh:

Anyway, NewEgg is good, go for it. :smile:
Stupid question, have you tried pugging the device into another plug, NOT on your serge proector, it may have been damged during the thunder storm, thats what there for.
lol, yeah, that could be it.
But it's unlikely. If you really have a surge protector and not just an extension cord with multiple outlets, it should be a fuseless protector, which will simply shut off if the voltage gets to high. If it's an extension cord-type, it wouldn't get hurt and only your PSU would die.

Unless you have a "surge protector" that's really old (does it have any LEDs on it?) then it's prolly not an issue.. my 2 cents.
My surge protector is SOOO cool, it is a 6 Socket Procector, with a 5 meter extention lead,

Each Socket has its own FUSE. ut if you have a new(ISH) surge proector, it could be its damaged, and keeps tripping out.