Fluctuating voltage levels....

I've been monitoring some voltage levels on a PC, and they jump around occasionally: the +12v rail has jumped as high as 15.74v and the 5v has gone down to 2.15v. These are extremes, and just real quick spikes, but I know it's not good and may spell some serious hardware failure in the future. My question is, is this the power supply? Or is it the motherboard? I'm using the free version of HWMonitor and the monitor from the motherboard maker's web site (Biostar) and they both record the same voltages. I'm leaning towards the problem being the PSU, but I guess it could be the mobo as well. Failing capacitors can wreck havoc on system voltages.... any insight?

Thanks!

 

The only way to properly test voltages is using a Multi-meter
Failing caps Look for swelling/buldging and leaking


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A PSU is so Improtant, but yet this where so many Cheap out.............

 

Yeah, I know what failing caps look like and they're all just fine. Testing with a multimeter would be a bit difficult because the voltage spikes high or low only once in a while... maybe once every 4-5 minutes (if that). If there's no draw on the PSU, it's hard to say whether it will spike as it has been. I really want to figure out what's up so I don't cause any unnecessary damage to any other components....

 

The voltages you specify are totally unacceptable and way out of tolerance, I would stop using that PSU and substitute it for another one as bad PSU's can damage other hardware.

When you said "If there's no draw on the PSU" do you mean your starting it up with nothing connected? It's best not to do that as switch mode PSU's don't like being run under no load, some have a certain amount of protection against this others do not.

Just because a capacitor looks ok doesn't mean it is, the only real way to check the goodness of electrolytic type capacitors is with use of an ESR(Equivalent Series Resistance) meter but it's not worth buying one for a one off test.

Using a digital multi meter for this test probably wont help much as they don't update there display fast enough to show fluctuations in the supply as these fluctuations could be less than a few microseconds, on an analog meter you may see the needle twitch but the best thing to use would be a storage oscilloscope but again not worth it for a one off test.

It's still possible you have a faulty mobo so drop another PSU in and keep an eye on the voltage. The other thing that could be causing this is dry solder joints in the PSU, try taping it and see if this changes the voltages as this new lead free solder isn't as good as the old leaded type

 

Yup. I know those spikes are totally out-of-control and as soon as I realized that it wasn't a one-time thing, I powered down until a new PSU was obtained. The last thing I wanted to do was to send bad voltage thru each component.

Done. I acquired a new Antec EA650 (click here for more info) and things are back to where they should be. I have a 5yr warranty on the spiking PSU so returning it won't be a problem (this is why we save recpt's! ). When I get the warranty replacement, I'll probably just save it as a back up unit....
:-D

ALL IS WELL!!! :celebrate

(BTW- the Antec EA650 is an EXCELLENT value for a PSU! Check the link I posted, and look at all the goodness: 80+ certified, 3 rails with FAT amperage, RoHS, nice unit! Only $100 at egghead)

 

It should really shut itself down in over voltage condition to protect itself and the other hardware connected to it. Maybe the manufacturer omitted this protection to save on production cost.

I'm glad you got it sorted

 

:cry :banghead IT'S NOT THE POWER SUPPLY!!!! :cry :cry :cry

I ran some monitors again (the same tools listed above) and it IS the motherboard! I even used a different wall outlet and a different surge protector just to be sure, and the erroneous spikes are hitting the same levels with a brand new power supply. On the plus side, we have the recp't for the motherboard too!

 

The thing to keep in mind is that those on-board mother board health monitoring chips are not wonderfully accurate, if your 5 volt rail is dropping as much as you say the system would keep locking up. It's unlikely your mobo is causing over voltage!