Computer rebooting due to low/fluxuating 12v rail?

[Helevitia]

Greetings,

I am looking at a friends computer for him because it reboots randomly. It even reboots right after POST sometimes so that basically rules out the OS. I started watching the voltage lines and instantly noticed that the 12v rail is fluxuating heavily between 10.62v-11.34v. As I was watching this, I was sure it would reboot, but it never did even though it rebooted constantly before I noticed this problem. Finally I rebooted manually and watched the voltage lines again. This time the voltage was fluxuating between 9.62v-10.08v! It fluxuated for about 30 seconds and then it dropped once to 9.57v and BOOM! reboot happened.
Before I chalk this up as a bad mobo, I just wanted some opinions from others.

Thanks,

Dave

[LvR]

I would ditch that sucker.

[Wombat]

Bad something, but I'd say bad PSU first. The MB doesn't do much to the 12V except use it. The HDs and other components use that line much more. Still, I kind of wonder about the PSU.

[Helevitia]

Good point! I'll check with a multimeter and see whats up. Thanks!

Dave

[UtwigMU]

I recently posted similar problems that friend's rig has.

Get him an Antec, PC Power & Cooling or something. Decent PSU is somewhat costsly, but it's worth it.

The voltages on 12V rail are also similar (10-11).

For instance flaky PSU can cause your box not to pass memtest86.


What are the specs and what's the PSU?

[Helevitia]

OK, I talked to my buddy and he says that he already changed out the PSU. The only about that though is the fact that it is a 250W generic PSU. I am leaning towards the mobo again at this point. Just for grins, I left it on the hardware monitor screen for about an hour. Usually it would have rebooted, but I went in and checked it and it was still on the hardware monitor screen with a solid 12.24v! It has now been 2 hours with no reboot and a solid 12.24v.

Specs:

Gigabyte something. It's the older original SocketA Athlon mobo with SDR PC133 memory.
Athlon 700
PC133 128MB
GF200MX
some nic card
built in audi0 - audio 97?


Dave

[K6-III]

Are the caps all in OK condition???

[Technoid]

Originally posted by Helevitia
OK, I talked to my buddy and he says that he already changed out the PSU. The only about that though is the fact that it is a 250W generic PSU. I am leaning towards the mobo again at this point. Just for grins, I left it on the hardware monitor screen for about an hour. Usually it would have rebooted, but I went in and checked it and it was still on the hardware monitor screen with a solid 12.24v! It has now been 2 hours with no reboot and a solid 12.24v.

Specs:

Gigabyte something. It's the older original SocketA Athlon mobo with SDR PC133 memory.
Athlon 700
PC133 128MB
GF200MX
some nic card
built in audi0 - audio 97?


Dave

No wonder its shaky with a generic 250W PSU

[rylan]

Yup.. 250w Generic power supply + older Athlon = unstable system

[Technoid]

Originally posted by rylan
Yup.. 250w Generic power supply + older Athlon = unstable system

well, anything higher than a P3 will be unstable on a generic 250w PSU

I have seen some High quality 250w psu's that did manage it before the user added a burner and a hdd, capture card, et etc

[Greebe]

Replace that PS. The Vcore rail required for the cpu is derived from the 12v PS rail. You must have a good PS to handle the loads the original Athlons placed on them. A 300w Powerman or similar will resolve all these issues and is AMD approved for that cpu.

Might I suggest any of Allied's PS's, 300w or greater

http://www.newegg.com/app/ViewProduct.asp?submit=manufactory&catalog=58&manufactory=1601&DEPA=0&sortby=14&order=1

P.S. also reccomended by AMD

[Gurm]

I too love Allied, my only complaint is that since their acquisition by FoxConn, it is IM-friggin-POSSIBLE to get them RMA'ed if they do die.



- Gurm

[Helevitia]

Thanks for all of the help everyone. I'll start with the PS then and see if things improve.

Greebe, am I really looking at the right PS for ~$20.00 dollars???

Thanks for the link!

Dave

[Gurm]

Yep. Allied are cheap, which is one of the reasons I like them.

- Gurm

[Greebe]

eYup you're looking at the prices