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Massive momentary voltage drop while idle

Last response: in Components
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February 20, 2013 9:26:57 PM

Hey all, I came home this afternoon and saw something pretty disturbing - at some point today it looks like my 12v rail cratered to around 1.5v, and my 5v rail went down to under 3.3v!! Don't know when it happened, as by the time I got home it was back up to normal, but this kind of freaked me out.

A little history - I was running a Phenom II x6 1055T, 8 GB Crucial Ballistix RAM and an MSI 560 Ti Hawk on an AsRock N68C-S UCC mobo inside of an NZXT Gamma case. I was getting piss-poor GPU temps (which I still am, and is about to be the topic of another thread) and I thought maybe my case wasn't cooling well enough. I also wanted to try overclocking the CPU but could only get a mild o/c on the AsRock board. So I decided to upgrade the motherboard and case. I switched them out to an Asus M5A99X EVO R2.0 and a Thermaltake Level 10 GTS. I'm using the same ps - an OCZ Fatal1ty 550w.

I switched all the components last week and have had multiple problems since then. One, as I mentioned above, is that the GPU is still running every bit as hot as before, but that's for another thread. Another problem is that I keep periodically getting warnings from the Asus software concerning my fan speeds and voltages. I've only seen 4 or 5 warnings pop up, but I run the computer 24/7 so it could be happening more often. Twice I've been warned about RPM drops on one of the three fans plugged into the motherboard, and I've noticed 2 or 3 warnings about voltages on one rail or another. Just last night I got a warning about the 12v rail, but it had dropped about 1% so I wasn't too worried. Still, since I can't watch it all the time I've been keeping HWMonitor up and running. This morning I reset the minimum counters, so I know the drop happened some time this afternoon while I was gone. The computer wasn't under any load, just a few windows open and not doing anything, and it's probably relevant to note that I haven't had any crashes or noticeable voltage drops when under heavy load like playing games. That's what makes this more disturbing, as it happened when the computer wasn't even really doing anything.

So, any thoughts? I could test with a multimeter, but as I've been watching the last few days the power has been pretty steady, with minimal fluctuation - this is the first huge drop I've noticed. Could I have gotten a defective motherboard, or is it more likely that my power supply is failing? Or could it be that the new motherboard and extra fans I've installed are drawing too much power? Any help here would be appreciated.



Note: As I was just about to post this I got yet another warning - this time the 3.3v rail dropped - HWMon says it dropped to 1.799. All of these drops seem momentary and go right back up to normal voltage. What the heck is going on here??
a c 702 ) Power supply
February 21, 2013 2:04:16 AM

Well if those drops where real the computer should shut down. Although that is the case I would try another PSU just to rule that out as the culprit.
Seeing the GPU temp on there as well being 50°C max is fine considering that the GPU has max operating temp of around 100°C and common that they run in the 70's°C.
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February 21, 2013 12:22:07 PM

Thanks rolli, I was wondering myself if the machine would have shut down at that low a voltage, so I'm wondering if maybe I got some bad sensors on the mobo. Unfortunately I don't have a spare power supply, so I'd either have to rip apart my other computer or buy a new one in order to test and I'd like to avoid that if possible. Is there any other way I can test the integrity of the motherboard before going the route of testing the ps?

Oh, and believe me, I'd love it if the gpu would stay in the 50's or even the 70's - I've got a whole other problem there, and have had it since I bought the card back in November, but I'll get more into that in a gpu thread.
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a c 702 ) Power supply
February 21, 2013 2:39:54 PM

It is hard to disregard it totally but it really is between the board or the PSU if it is not just a software issue. Might be worth getting the PSU out of the other computer to test.
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February 22, 2013 5:57:12 PM

Thanks rolli, I'll consider doing that when I have some spare time.
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