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-   -   Low 12V rail on Corsair AX1200 (http://www.hardwarecanucks.com/forum/power-supplies/45449-low-12v-rail-corsair-ax1200.html)

Prolab August 6, 2011 01:59 PM

Low 12V rail on Corsair AX1200
Is it normal to have your 12V rail lower than 11.58 volts?

I just noticed it now when i was looking at HWMonitor. When i had my XFX BE 850, i dont remember seeing the +12V rail that low. Even when using prime95 or MSI Kombustor to simulate load - the value keeps going lower actually. Is that normal?

I thought it would be closer to 11.8+ or at least as close to 12V.

Here's a screenshot (you can zoom in if need be):


SKYMTL August 6, 2011 02:02 PM

HWMonitor isn't accurate in the least.

_dangtx_ August 6, 2011 02:31 PM

break out your multi and see what gives.

i wouldnt worry about software/sensors buggered up.

i have the little brother of the 1200 here on an asus board and it tells me 5v on the 12 lol. yes,in bios too...

frontier204 August 6, 2011 02:46 PM


Originally Posted by SKYMTL (Post 538885)
HWMonitor isn't accurate in the least.

+1 don't trust those software-based voltage readings. OCCT told me my parents' computer had 4.5V on the 5.0 line, but my Agilent multimeter told me otherwise. For that matter, if you really want to diagnose a PSU, use an oscilloscope (available for the price of a GPU on robotics hobby web sites).

There's a reason why I (and I hope a lot more others) ignore any power supply reviews that use software or multimeters for their voltage readings.

EDIT: close up a loophole in last sentence ;)

_dangtx_ August 6, 2011 02:48 PM

hey whats wrong with mutimiters lol?

better than software readings any day! :)

frontier204 August 6, 2011 05:07 PM

1 Attachment(s)
I'll admit a multimeter's better than using software - at least (if your multimeter is working and used properly) won't tell you that your +12V is giving less than 8V hehe. [see attached picture if I don't delete it for fun]

Multimeters can't detect the very high frequency ripple which can also damage hardware. If your PSU is sending small spikes or lots of ripples that are milliseconds in length to your hardware, the multimeter won't see it unless your lucky but your hardware may still take damage. Unless your multimeter is tuned for high frequency for some reason, it will just average out the reading and tell you that your +12V line is outputting 12.06V even if it's bouncing quickly between 11 and 13V or something.

See your favourite cheap exploding PSU review by Hardware Secrets / JohnnyGuru for details, like this one:
Example: Diablotek RPM-1050 1050W Review
In the review it looks like for them the multimeter (or scope taking the average like a multimeter does) shows "meh" voltages, but the ripple, which most DMMs won't see, increases as load increases.

Prolab August 6, 2011 07:58 PM

Gotcha, took out my DMM and checked BIOS... +12V is around 11.93. Thanks guys!

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