mysterious, sudden shut downs

[spindoc]

my system config is as follows:

Intel Pentium D 820, 2.8 GHz ( not overclocked)
ASUS P5LD2-VM SE( has an Intel 945G chipset) with onboard graphics( GMA 950)
2*512 MB DDR2 RAM- 667 MHz (of clock cycles 5-5-5-15-21)
Seagate 160 GB SATA II HDD
a PCI sound card
Technotech cabinet with generic 400W PSU
17" LG Flatron CRT monitor
500W Microtek UPS

problem is that, sometimes while watching movies or playing games or browsing the net, my pc suddenly switches off, without any warning. this has been happening from the time i got this system one and a half years ago.

any effort to restart it immediately after are always futile.but when a gap of 15-20 minutes is given, it restarts and works smoothly. i suffer from these mishaps atleast 4-5 times a month.

can anybody plz point out which unit is malfunctioning.

thanks

[dheeraj_kumar]

You need to look at every single fan inside your case, including the cpu fan, and check if they all work correctly. And if they all do, then it may be a overheating problem. Check your processor and hard disk temps using Everest.

[topgear]

Do what dheeraj_kumar suggested 1st.

But I think your PSU is the culprit.
Last year I also faced same prob with my old rig. Changed the PSU & my prob solved.

[pimpom]

dheeraj_kumar's and topgear's suggestions have merit. Let me add some other considerations. Your problem sounds like a heat-related issue, but this does not always mean that something is truly overheating. A defective part may be OK when cool, but cause problems when it has warmed up. This is a strong possibility since the problem was present even when the rig was new.

I suggest you also test your RAMs thoroughly with memtest86.

See if proper airflow is obstructed by messy arrangement of the cables inside the CPU.

Since you're using two RAM sticks, try running your computer with one stick at a time and see if the problem occurs.

Pull out all connectors and re-insert them firmly. With the mobo PSU connectors and the Molex connectors to HDD and optical drives, push each wire separately and see if one or more feels just a little bit loose.

If there's a known good PSU you can borrow, try running the comp with that and see if the problem still occurs.

[Dr.tweaker]

u told that u r using 2 ram sticks,have u matched their frequencies,though mix and match is possible,but still check for it

[phreak0ut]

You should have taken your system to the dealer when you started facing problems. Well, coming to the problem. Try keeping your cabinet open and test it. Like others said, if cooling is not the problem, you should first replace the PSU. I also suspect that UPS also might be at fault. Try connecting your system directly to the AC outlet and check.

[pimpom]

Originally Posted by phreak0ut

I also suspect that UPS also might be at fault. Try connecting your system directly to the AC outlet and check.

I second that. In fact, it was one of the things I meant to suggest, but forgot to include while typing the rather long list of other possibilties.

[spindoc]

Originally Posted by dheeraj_kumar

You need to look at every single fan inside your case, including the cpu fan, and check if they all work correctly. And if they all do, then it may be a overheating problem. Check your processor and hard disk temps using Everest.

i have only a single CPU HSF, no other fans except the one in the PSU. all are working nicely.

[spindoc]

Originally Posted by pimpom

dheeraj_kumar's and topgear's suggestions have merit. Let me add some other considerations. Your problem sounds like a heat-related issue, but this does not always mean that something is truly overheating. A defective part may be OK when cool, but cause problems when it has warmed up. This is a strong possibility since the problem was present even when the rig was new.

I suggest you also test your RAMs thoroughly with memtest86.

See if proper airflow is obstructed by messy arrangement of the cables inside the CPU.

Since you're using two RAM sticks, try running your computer with one stick at a time and see if the problem occurs.

Pull out all connectors and re-insert them firmly. With the mobo PSU connectors and the Molex connectors to HDD and optical drives, push each wire separately and see if one or more feels just a little bit loose.

If there's a known good PSU you can borrow, try running the comp with that and see if the problem still occurs.

none of the wires are loose. there is proper airflow inside the cabinet. i have kept all the dangling wires bunched up and glued together with duct tape.all connectors are firmly in place.
can't borrow a PSU as most of my friends have laptops.

[Zangetsu]

me 2 facing the same problem...

there is more chance of faulty PSU.....
but also RAM have 2 be checked....

i dont use floppy...so i need a bootable CD of memtest86...does anyone knows the link

[spindoc]

Originally Posted by Dr.tweaker

u told that u r using 2 ram sticks,have u matched their frequencies,though mix and match is possible,but still check for it

both the RAM sticks are of the same frequency and clock cycles.
more so even if they were mismatched the system would have downgraded the faster RAM to the slower RAMs' clock speed.

Originally Posted by phreak0ut

You should have taken your system to the dealer when you started facing problems. Well, coming to the problem. Try keeping your cabinet open and test it. Like others said, if cooling is not the problem, you should first replace the PSU. I also suspect that UPS also might be at fault. Try connecting your system directly to the AC outlet and check.

earlier i had connected the PC directly to the AC outlet, but the problem had persisted.
the thing is that the frequency of these sudden shut downs had decreased over the months and have recently restarted although there has been no change in my configuration.

[pimpom]

Originally Posted by KaranTh85

i dont use floppy...so i need a bootable CD of memtest86...does anyone knows the link

http://www.memtest86.com There's an ISO image in the download section, ready to be burned to CD. It's only 46KB zipped. If, for any reason, you cannot download it yourself, send me a PM with your email address and I'll send it to you.

Originally Posted by spindoc

none of the wires are loose. there is proper airflow inside the cabinet. i have kept all the dangling wires bunched up and glued together with duct tape.all connectors are firmly in place.
can't borrow a PSU as most of my friends have laptops.

It looks more and more as if it's the PSU. And it is almost certainly a heat-related problem. If you or a friend have some experience in electronics, you could open the PSU and see if the power transistors are firmly screwed on to their heatsinks.

Have you tested your RAMs with memtest86 ? And have you tried with only one RAM stick at a time as I suggested earlier ? This is important as one of the sticks may be faulty.

You can also try underclocking the RAMs at 533. I have occasionally seen some cheap no-name RAMs run OK when underclocked, but cannot manage the rated speed.

[Zangetsu]

^ Hey if the RAM is faulty then what type error message is displayed...

And is it a trial version software....

[pimpom]

Memtest86 is freeware. Not trial or demo.

You create a bootable floppy or CD with it and use it to boot your computer. It boots into its own DOS mode and automatically runs the test.

At its default setting, it runs a series of eight different tests. Depending on the speed of your system and the amount of RAM, it takes about 15mins to an hour to complete one cycle of 8 test modes.

The screen is blue with white text in the upper half. If it detects any fault, it displays the location etc with white text on a red background in the lower half of the screen.