pc keeps rebooting without warning

[sintan]

my pc keeps rebooting randomly! it usually happens about 3 to 4 times in an hour then will run fine for a few weeks, giving me with a false sense of security, then it returns!
i was experiencing a particularly bad run of it last night and it shut down without rebooting at one point, i unplugged the multi adapter plugged it back in and heard the faithful humming of 'standby' then rebooted myself...

i've read up on similar problems, i've turned off auto reboot upon error, but get no error so think its definatley a power failure. i've been inside the chassis and checked every cable, power lead and firmly placed ram in the slots.

also note that a few weeks ago it failed to reboot totally, i swapped the power cable for another which worked fine.

i connected the pc straight to the wall socket and not the adapter, but the problem persists.

sometimes it reboots before windows has attempted log in, i entered bios and left it for a while, the pc rebooted even from there!

i have unplugged all peripherals, tv-out cables etc, to no avail.

also, would a surge protector help my situation or are they only useful against storms?

thanks in advance

SET UP:
windows xp pro SP3
nvidia 8800GTX
corsair HX psu
3.5 GB ram

 

[patonb]

Check the events log in the control panel.

It might tell you.

 

[QuaziBee]

Either you are over heating or your PSU is failing.

It's probably not a software issue if it's happening at truly random times.

Download (coretemp?) a reputable heat monitoring program and check your temps. If they are low and steady, all of them as I damaged my NB heatsink once and thought the reading was faulty, then it's a 99% chance your PSU is failing. If you have another one from another, or a friends, computer with ample wattage try swapping it in for a while.

If it's not one of those two it will be a pain in the *** to troubleshoot.

 

[sintan]

thanks for replies ppl, will try your suggestions soon as i get home in the mornin!

 

[Dauntae]

My backup workdog PC started doing the same thing, I had 2 HD and just added my 2nd DVD burner and it would stay on for a little while them just start rebooting non stop. So I borrowed an extra PS from a friend (a cheapo that came with his case) but it solved the problem. The old one (real old) could not handle the extra draw of the dvd so I ordered a real good one for the main system and this one (Rosewill 480W ) is going to the backup system. So my guess would be the PS because mine was doing exactly what you described and didn't always do it, My guess is a cap started heating up and caused a reboot.

Dauntae

 

[sintan]

k, soon after my original post, the reboots become more and more frequent the longer i had the pc turned on, so naturally put it down to overheating.

i tried one ram stick at a time (from 4 1gb sticks) in different slots - no change.

all fans are running well.

i took the entire system apart, cleaned everything, re-applied arctic MX-2 to the cpu and north bridge. south bridge has a thermal mat which seems fine.

after putting it back together again, the reboots happen less often, but are stil happening.

i tried memtest86 with each stick in for about an hour while in different slots and all reported fine without rebooting. when i used 3 or 4 sticks together it started rebooted after a about 2 hours, but still reported no errors to the ram, so again i think something is overheating. i had the HDs and dvd drive unplugged during the mem tests.

my cpu temps are in the low 30s, the system temp is about 40-ish i think.

the voltages are reported as normal by the mobo.

the pc reboots more often when in windows due to more stress on system, but i'm convinced its not software related due to reboots during startup and memtest.

pcmark ran once without problems, and again with a reboot.

3dmark caused many reboots often, which i guess would point toward the GFX, which brings me to another thing.... i recenlty started using an s-video lead to play old games through a crt tv. i noticed sparks when the adapter touched the metal exposure of the GFX card at the back of the computer!
could that have damaged the card with electrostatic charges?
also, getting the lead plugged in required some wobbling and movement of the gfx card while the system was running....

well so far i think its down to the GPU or PSU and i'm trying to get hold of someone's spares to test them.

also, the PSU is a good corsair 550w so can surely handle the load...

what are other people's thoughts on this?

thankyou

 

[GoodNews101]

Yes, Corsair makes good PSUs but even they can make one that fails. Are you able to borrow a digital multimeter to test the output of the psu? I have a Craftsman digital that I got for $20 and it works great.

Also, the rule on memtest is a minimum of 7 passes. I find it interesting that with one stick the system is stable but with 3-4 sticks the system crashes. Have you overclocked and what does the BIOS say about the timings and voltage of your RAM?

As for damage and electrostatic charges I say if one single, small electrostatic discharge from one finger can fry a motherboard it is a good hunch on your part that your Video card is the culprit.

Let us know if switching out the cards helps. I just hope those sparks from the adapter didn't damage the video card slot on your motherboard.

 

[sintan]

i'v got a multimeter on its way this week.

i put each ram stick through the test twice, the pc reboots when testing all ram together. it takes MUCH longer to put all 4 sticks through 2 tests, so i think the reboot is due to the system, being on for longer as is consistant, thus i doubt the ram being used together is the culprit.

the BIOS reports the ram timings at default frequency 800 and 5-5-518. the voltage is 1.236v.... normal?

if the sparks did damage the video slot, could that slot damage another card placed in it?!

something i forgot to mention - when i was cleaning the old arctic MX-2 thermal grease from the cpu, i noticed i had used alot last time, and a little bit got between the heat spreader and the actual cpu, could this be a problem?

 

[patonb]

Mx-2 is non conductive, so most likely not.

 

[Baez]

Please do not double post sintan. Use the edit function.