PSU Dying?

amd

HELP!!! I feel I might be stating the obvious here, but please be gentle. I'm not too hot on electricals so not sure what the problem is.

I keep an occasional eye on my power usage with Winbond Hardware Doctor (came with motherboard). Lately my +3.3v and +5v levels have dropped to just above their low limit, they're about 3.15v and 4.63v. The warning alarm even came on a couple of times yesterday. However, I haven't installed or done anything recently.

I've ordered a new PSU from Ebuyer - just the cheaper one as the computer is 4 years old and I reckon I'll be overhauling everything in a year or two anyway. It's more powerful than the one I've got so I hope I've covered myself. Have been Googling, but going round in circles!

Questions: What else could it be, if anything?

Am I safe to continue using this in the meantime? (Will keep the prog in the background just to keep an eye on things.)

wolfman

No, I'd stop using the computer until the new one comes.

At a minimum you want to be within 5% of the ideal voltage. So for the 5v rail, you don't want to go below 4.75v, and for the 3.3v rail, you don't want to go below 3.15v. For me that's generally an absolute minimum.

It's worth unplugging any extra devices you may not be using. USB devices for example, or extra DVD-Writer, extra hard drives. Doing so will reduce the strain on the psu.

I'd be careful buying one of the eBuyer psu's. A high wattage doesn't necessarily mean a good psu. I ran my previous setup on a 380W psu, and it could handle quite a powerful gaming system.

If you do decide to get a new machine, in future it's worth spending a little extra on the psu. £40-50 will get you a decent psu. £60-80 would be about the maximum for me. It sounds like a lot, but is definitely worth it. The bargain I always recommend people is the Antec Sonata II. A brilliant, well built, and attractive case with a quality 450W psu, for only £80. It's the backbone to any system I build for friends.

wolfman

If you want to understand a little more about the PSU, and what your requirements may be, here's a very good article.

http://www.bleedinedge.com/guides/psu_select/psu_select_01.html

amd

Hi Wolfman, thanks for the reply. As I said, I have been googling, and as far as I could work out (if my memory serves!) the 3.3 and 5v power the motherboard, CPU, graphics card and memory - can't do without any of them! The 12v does the hard drive, and CD/DVD drives and case fans. I did unplug my usb scanner but didn't make a difference. I can't get my head around what else I could do! Please correct me if I'm wrong. I'm reading this stuff but it's gobbledegook to me!

wolfman

You're on the right track, it's not quite that simple though.

I think the cpu, or at least more modern ones, run of the 12v rail. Things such as the graphics card usually run off a combination of the 5v and 12v rails. Most devices will take their power from a combination of rails. I think usb devices run on the 3.3v rail (I used to be able to make mine go up and down when I unplugged my iPod, Camera and Phone) but may also take power from the 5v rail too.

From the sound of things anyway you probably won't be able to make much difference. I'd wait until the new psu comes.

Joe_Bloggs

Wolfman is right. You should also take a look at the state of the capacitors on the motherboard. If they were leaking/bulging then they could have been putting extra strain on the power supply. The power supply is also packed with capacitors that may have been substandard and started to leak. It is always worth backing up any useful information. Try excercising this sytem with new PSU, without the hard disk as errors could trash the system on the hard disk.
Try an Emergency boot CD/memtest86 to see if things are in order prior to booting into windows again.
J_B.

Toxteth_OGrady

As Wolfman alluded, P4 and Athlon onwards rely on the 12V rail, as do AGP 2 and later graphics cards. In fact a large number of newer graphics cards take a 12V supply directly from the psu as well as from the AGP slot.

Look for a psu that gives you at least 16 Amps on the 12V rail. Check the specifications online before you buy or look at the label on the side of the psu.

Be careful choosing cheaper brands; they often specify maximum peak power available which can be very misleading. Q-TEC are particularly guilty of doing this.

Use this very good online PSU wattage calculator to determine what you need for your system.

:cool:

TOG

wolfman

Toxteth_OGrady wrote:

Look for a psu that gives you at least 16 Amps on the 12V rail. Check the specifications online before you buy or look at the label on the side of the psu.

If 16A (or in that region) make sure the psu has dual 12v rails. Most decent psu's will have two 12v rails so that the load is balanced. This mainly done for safety reasons so that one rail doesn't carry a huge amount of current ad instead it's divided between the dual rails. This isn't standard though.

What matters is the total 12v current. As a total (on the 12v rail) 22A would be recommended, if not more (if you have a P4 or equivalent system). For example, a dual rail psu may have 8A on the first 12v rail and 14A on the second 12v rail, totalling 22A.