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Is my PSU dying, or is it something else?

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July 1, 2012 12:26:04 PM

Hello,
I have had ongoing issues for a while, ever since upgrading both the GPU and PSU on my PC.
Spec: Corsair CX600 PSU; Geforce 315 GPU; ( awaiting return of 550ti,) 8 g RAM; i5 650 CPU.
The GPU failed and a replacement is on the way in the post. I returned to using the old 315. I have been monitoring the voltages etc. very closely, perhaps too closely; the temps have been fine, but the voltages have not. I have been using CPUID hardware monitor; as speedfan refuses to show the voltages. Under no load, the 12 v rail shows as fine, but the 3.3 v rail shows as 1.35! However bios states the 3.3 is in fact 3.3.
I have been keeping HWonitor on whilst playing games and most voltages remain stable, (even if one is wrong! ) however the 12 volt rail drops as far as 10.47! I was still able to play the game though, only noticed after stopping playing.
Questions: Is the PSU failing, ( its sixth months old, ) or are the sensors faulty? For that matter could it be the mother board? Or should I stop worrying and get one with it? I intend to run a test with a psu tester this afternoon.
What makes it a bit more complex, is that we get mains supply power drop outs infrequently; I have ordered an uninterupted power supply to stop that issue.
Thing is I have no idea why the GPU failed, it could have been just that, but I cannot help wondering if there is another cause.

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a b B Homebuilt system
July 1, 2012 12:50:28 PM

ignore that 3.3V rating as it is obviously wrong. If you were really running that low then the computer would simply not work.

For the 12V you want to be within 10%, and the 5V and 3.3V you want to be within 5% when under load
12V can be 10.8-13.2V
5V can be 4.75-5.25V
3.3V can be 3.135-3.465V

If you are hitting 10.4V then I would first look into getting a little bit of power conditioning (a power bar, or battery backup that has a regulator built in). You should have this anyways, and it can help if your home is older and does not have the capacitance needed to supply modern equipment with highly variable workloads (some modern homes actually add capacitors now to take some of the odd loads of computers, CFLs, and other devices that cause issues). As your voltage is so close, I would bet this is part of your issue.

If that does not clean it up, then it is time for an RMA, or a new PS
July 1, 2012 3:00:24 PM

Can I ask for a bit of clarifiaction there caedenv?
Are you saying that the uninterrupted power supply could help?
Or is it something else you are refering to?

Our home is in fact a little less than five years old. However the power supply infrastructure in our are has had problems in the past.
Under light load the 12v rail is showing as rock steady, which is what is confusing me. When I stress things, either through playing a game or running a stress test, it drops off. It went to 10.47 like I said, which should have caused the game to crash shouldn't it? But I only realised there was an issue after I stopped playing and checked the HW monitor, saw how low it had recorded. I saw no problems in game, or in any other way.
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a b B Homebuilt system
July 1, 2012 6:52:55 PM

being outside of that 10% rating will not necessarily cause immediate issues, but it will cause problems over time via a shortened lifespan on parts, or the power supply itself.

The power grid is meant to run things such as fans, engines, and compressors that are found in your fridge/HVAC/washer/drier/etc, and things that heat up like old edison lighbulbs and heating elements. These things all have a high current to start, but then level off for a long relatively low, but consistent power usage.
Computers on the other hand will run at 2-5W in sleep mode, 25-100W in active idle, 75-150W under normal use, and then jump up to 500+W when doing major work such as playing computer games. And the whole time that wattage is variable, instead of running at a singular consistant power consumption rate. It's not that it is a bad thing, but the power grid in older areas is simply not made for it. It is such a problem that some new homes will have a capacitor built into the home to help alleviate some of these fluctuations, and newer negiborhoods have a great many more capacitors and transformers on the telephone poles compared to older ones, all to help average out the load more over time for the power stations.
Living in a newer neighborhood (you said your home is only ~5years old) it should not be an issue because current electrical code is set to be able to take the hit of these newer devices. But older negiborhoods like mine are ~60-70 years old. In fact, my home is so old that it originally had ~5 lights, and a grand total of 11 outlets, and no ground. But the point is that while I now have a modern electrical box, grounding and GFCI in most of the house (excluding the original circuit), and much higher amperage service than it had originally, the local electrical grid was simply not meant to take the kind of load I (and my neighbors) put on it with our computers, TVs and consoles. Plugging a gaming rig into an outlet without a battery backup around here is simply suicide. Even with a decent power supply that will clean up a lot of the local power issues, the voltages in my rig are well below where they ought to be when pushing the system. But you throw it on a battery backup that prefilters and buffers the power flow and my rig runs within ~5% of what it is rated, which is great!

So, all that to say: Yes, a battery backup, or a power strip that does a bit of filtering (something more advanced than a simple breaker) can make a huge difference, and is a great precaution to have in any area prone to high winds, electrical storms, power outages, or generally sub-par power situations.
No, having your voltages off even as much as 15% (you are at 12.75%) is not going to necessarily cause stability issues in your games, because electronics makers know that most households are not in 'ideal' power situations and design some fault tolerance into their hardware. But it is going to put more strain on your hardware, which will lead to shortened lifespans, and can cause odd issues over time.

So it can help, but it does not rule out the possibility that you simply got a bad power supply. But regardless of your power supply, you should have some form of filtering, or battery back up in place 'just in case'
a b B Homebuilt system
July 1, 2012 7:48:12 PM

If you got down to 10.47 V your system would have crashed out hard, try to use a different program to check the voltage or update your version of HW Monitor, it takes them a little while to get the voltage readings straightened out with newer motherboards.


Now to clarify some important points, ATX spec says that the primary rails (12 V, 5 V, and 3.3 V) MUST NOT exceed +/- 5% of their nominal value, this isn't optional, any variance outside +/-5% is considered to be a failure of the power supply unit. 10% from nominal is only acceptable on the -12 V rail since almost nothing uses it and it is very low power.


As for if a UPS would help, it is important to realize that the output of a PSU is independent of its input, a modern PSU with active PFC doesn't care if you are feeding it 100 V, or 260 V, it will still have the same output voltage regulation so a UPS isn't going to help with an output voltage problem since the APFC circuit boosts all incoming voltages to the same level so the primary and secondary side of the PSU are behaving the same regardless of the input voltage.


ATX spec is pretty loose already and electronics are very very sensitive to voltage fluctuations, a 5% drop in output voltage would cause significant issues with the system, likely a total crash or lockup, 10% would just result in the power circuits for the CPU and GPU having insufficient power to work with and having to stop functioning causing the system to shut off.





I think what is most likely to be your issue here is software reading the voltages incorrectly. What I would do is use a multimeter and backprobe your ATX connector to see what the voltage is when the system is in use, PSU testers cannot load up the PSU so you can only check the no load voltages unfortunately.
July 1, 2012 8:16:50 PM

Thanks guys, interesting answers.

On the subject of the mains supply: as far as I am aware the supply in my area was only just sufficient for the previous homes, which were all built about 50 years ago. There have been a lot of issues in the area in tha past 5 years. The area is split into two supply souces, ( both join to a single source upline, so to speak. ) We live on the half which whilst having intermittant micro power cuts, some apparent brown outs, we can go months with a stable supply. The other half of the area has had many proper power cuts, lasting hours. The power suppliers have done much work to increase stability, they say they have it solved. They have not. I intend to phone them to tell them so. I have a UPS on order.

On the subject of voltages: I have just had the back off and tested the PSU again with a tester, which shows all fine. I will test tomorrow now, with a multi meter. Having just reconnected everything and started the HWmonitor, it says the 3.3 volt rail is in fact 1.35v, which just cannot be, can it? It also says the 12 volt rail was 10.03v, again which seems silly. It is still reading 1.35 for the 3.3, but now shows 12.3 for the 12v rail. The fan speed also started slow it said. I may have imagined it, but things seemed a bit slower, I don't really know.

This afternoon I checked the voltages in bios, they showed ALL the rails to be normal and very steady. I will check again in a moment. I tried to use Speedfan to get a second opinion, but it refuses to show any voltages at all. Can you suggest any other software monitor? I will also put the system through its paces to see what happens.

Thing is I am nervous about putting the 550ti back in, in case it decreases the stability further.
!