Testing Your PSU Rails

[mjn]

I need to measure one 12v rail on one my PSU's as the software states its running at 13v !

[SaFrOuT]

Just wanted to give another prove that motherboard monitors are so crappy
please check those results here

hope it will be helpful

[klebs89]

Got my radioshack multimeter so i can test my new PSU (OCZ Modstream 420, sshould be here this week), and tested my old psu which was giving me problems and limited my ocing (Virtually no proccesor, little videocard). Decided to post my results in this thread.
idle-3.34 load-3.34 mbm5idle-3.28
idle-4.93 load-4.96 mbm5idle-4.08
idle-11.77load-11.67mbm5idle-11.19
idle is desktop. Load is 3dmark05. Mbm5 Idle is desktop.
as we can see, mbm5 is definetly not accurate. It's also apparent my PSU sucks. While the 3.3 and 5 are decent the 12volt rail sucks. The PSU is a turbolink 420W. (Came with the case)
Rails are as follows-
3.3-28a
5-40a
12-18a
-12-1a
-5-1a
Powering
Gigabyte GA-8knxp
A64 3000+ (Newcastle, stock because of this ******ed psu)stock hs/fan
2*512 Generic Ram
6800GT@425/1080 (Limited by retrded PSU once again)
SBA 2 Value
2 optical drives
1ccfl
5 led fans and 2 non-led
Attached are pic of the test setup, multimeter, psu, and mbm5 readout. The Cam is good, but my hands shake so the pics suk. The white on the PSU is a reflection of the flash.
I hope this post helps convince people to
A) Get good PSU's
B) Not trust software readouts.
EDIT: Got my Modstream, see results in my review.

[Fangs404]

this is an extremely helpful resource. i just bought a multimeter yesterday and wanted to test it out, so i came to this thread. my +12V was reading 11.80 on speedfan, but when i used the multimeter, i got a nice solid 12.08. that's quite a difference. thanks for the info!

[paulpjs]

Yes, this voltage measurement is really the only way to tell. I've now had two Antec power supplies drift out of spec.

Read all the sordid Antec failure details

Really, this picture says it all:


Should be 5.0 volts!!

[davidhammock200]

Interesting. I use Antec's in lots of builds & they have always been very reliable.

Antec's have a 3yr warranty, did you RMA these to Antec & what was their response?

Dave

[tayts1]

****!!! while testing the rails of my psu, i accidentally allow the probe to touch the casing and cause the psu to trip!!!

after that, during the first few time i tried to on the computer, it somehow trip after a few second and on by itself again for a few time... i change the psu and the same thing happen... after a few more try, it apper fine... hope i have not kill the mobo...

guys, becareful when you test the rails...

Edited:
confirm i "injure" my mobo ****!!!

[Dave_Sz]

This thread helped me a lot.I dug out my trusty Fluke 77 series II and got to work.

Speedafan(load or idle) / FLUKE(load)
vcore 1.442-1448 / 1.432-1.438
+12v 12.65 / 12.21-12.23
3.3v 1.50-1.65 / 3.40-3.41
5vcc 4.96 / 5.11

[expert]

I think it is normal that BIOS always read a bit less voltage than if we measure directly on rails.
This is because bios measure voltage right before they go into filter circuits and regulation circuits and between them and rail are LONGGG PCB lines that because of high currents act as resistors.

If we can measure voltage right on where mobo sensor read it, and measure between that test point and rail line for that voltage, im sure that we will get readings which will by OhmLaw confirm that BIOS read voltage correctly.

Also these cheap meter are under specifications just if they measure clean DC voltage without ripple in it. Thats one more reason to use FLUKE.

I know that because we=hen I do monitor repairs sometimes these cheap meters just measure some stupid reading because ripples are present.

FLUKE 10 is minimum for reliable readings.

Correct me if im wrong.

(sorry for bad English)

[ShaTR]

I have an enermax 430watter, but from the day i got it, it reads slighly on all except the 12v rail, and slighly fluctuates on the 5v rail, as well as vdimm under stress. THIS NUMBERS ARE FROM MBM5, NOT A MULTIMETER

3.3v Rail - 3.25 rock solid
5v Rail - 4.94-4.97 slight fluctuation
12v Rail - 12.08 rock stable
bat 3v - 2.98 rock stable
Vdimm - 3.14-3.18 under load fluctuates

i was told this would be more than nuff power for my setup at 2.4Ghz daily running speed (see below). I don't have any concerns as far as stabliity goes, as my system never crashes. I was under the impression that some fluctuation is normal, but now im not so sure

My questions are

1. should i be concerned about my 5v and vdimm??? I do intend to test with a multimeter, but should i expect to see the same degree of fluctuation???

2. Im sorry if this has already been covered, but how do you test both 12v rails on a dual 12v rail PSU. I have tested before at a molex for 12v, but can't remember what it was at. just that it was over 12v.

[FireFly]

Ok this thread worries me. I know you people say that software shouldn't be trusted for voltage levels, but you people all seem to get software readings that say the rails are below what they actually are. My Asus probe reads out 12.8-12.9V on the 12V rail, should I be worried? :S

[Tim]

Originally Posted by FireFly

Ok this thread worries me. I know you people say that software shouldn't be trusted for voltage levels, but you people all seem to get software readings that say the rails are below what they actually are. My Asus probe reads out 12.8-12.9V on the 12V rail, should I be worried? :S

Typical Software rating (as in it's never accurate ) ....check with DMM and you'll SEEE THE LIGHT!! *ahem

[Danny5]

I have been using multimeters for a few years now to check PSU's when there are problems.

I have seen bios 12v voltages more than 0.5v volts off.

To all who are asking if their software voltages are a concern, there is only one way to find out for sure, see the first post on this thread.

Excellent tutorial BTW, I never thought to test voltages at startup and shutdown, where most voltage problems probably occur.

[drake85]

My 12v reading is close to minimum but then again I have a crap load of fans in my case (soon to change with a new case). BTW, the old AUX connector was for ANCIENT pieces of hardware, most before Pentium 2 times. MOBO's used it before ATX was standerdized, after that it was pretty much dead. Thanks for the tutorial. According to Abits readings my 5 volt was at 5.5 and the darn alarm wouldn't shut off. Now I know that the 5 is actually around 5.15 and seems to hold steady there. Thanks again!

[Danny5]

I have discussed this topic on other forums also. A "professional" electrical guy told me that you can't trust cheap multimeters, that you need to spend big bucks to get accurate readings. Does anyone have any insight on this?

For me, I use a Craftsman digital multimeter. I paid like $25 bucks for it. Dunno, the last PSU I tested was within 0.01 volts of the 3, 5, and 12 volt rails. I also tried it on my 120 VAC in the house, and it was within 1-2 volts also.

I know one thing though, I feel much more confident with the multimeter reading than what is showing in the bios.

BTW, I take the voltage readings right at the connections to the motherboard. I am not sure that taking voltage measurements taken off of an empty molex is truly accurate? I literally go through all power connections on the ATX power connector, and any other places that the particular PC has.

[davidhammock200]

Most "cheap" DMM's are good enough for our purposes.
If we can get +/- 5% on the second digit to the right, then we are fine.

[jon_n85]

I got the xion power real 600 watt power supply.

This one: http://www.newegg.com/Product/Produc...82E16817190007

This was my first "real" power supply and I was shocked to find out how unstable the rails were. The 5v+ rail is solid but the rest jump l like crazy, especially the 12v rail. I started researching this when my asus probe showed a dancing vcore. The vcore would jump from 1.38 to 1.44. I oc'd a a64 x2 4400 to 2.4ghz thinking it would be a conservitive overclock but I rather not put my faith in this psu. This is my first oc experiance by the way

The 12v rail jumps from 11.80 to 11.96 anytime I load an app. From what I have read here, it looks like I should return it to newegg but the funny thing is that I have had virtually no problems at with it. Even passed prime95 for 16 hours without even a hiccup.

Am I too anal about this or do you guys think I should replace it for this model: http://www.newegg.com/Product/Produc...82E16817103931 ?

Any advice would be much apreciated

[zetachi]

Ok I just tested my TT Silent Pure Power PSU on my rig and my 12 v line seems to go anywhere from 12.17 @ post to 12.24 when windows is loading 12.22 @ windows login and then anywhere from 12.13 to 12.28 when running apps. Is this bad? And may this be the root of all my problems (I just installed an X800 pro vivo unlocked to 16 pipes w/ arctic cooler 5) System was fine with my XFX 6600GT AGP before. Now I am constantly geeting BF2 crashes and BSOD (see my other thread http://forums.extremeoverclocking.co...41#post2127141 ) Any advice?

Thanks

Zetachi

[davidhammock200]

The Antec True Power II 550W is a very good PSU.

The less the fluxuation the better. PC P&C & OCZ PowerStreams rarely show any fluxuations.

If fluxuations are under 3% on all rails, I wouldn't worry too much.

[adil_hidayat]

call me stupid..
what is a sticky??