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SOLVED Little Help Measuring my PSU with a Multimeter?

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Mar 18, 2015
Ive made a thread about troubles I have been having with one of my machines and this is it :)

Dont be fooled by the title, I havent ruled out the psu. As a matter of fact I have decided that the PSU is first on the chopping block to be replaced...again. Before I go and do anything drastic I thought I would try some other troubleshooting, such as measuring the rails with a DMM. DMM and I are not real good friends. DMM usually doesnt tell me what I want to know, and I usually dont know what it is saying when it does (well its not that bad, but I really hate using them and do struggle to make certain I have done everything correctly).

I am following the guide in the sticky (here) and have a question.


from the pic... what is the AUX connector? I know Molx, SATA, CPU, 24pin ATX, PCI-E and all the other connectors on my PSU but I do not recognize any of them to be AUX. I did also run a search and dont recognize the images in the results (well some of them are recognizable, but as I said before I dont know any of them to be the AUX). So .... how do I go about this now? Where is the AUX ? Thanks in advance for your help guys
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Is there no Molex free? You don't need the AUX if you have a Molex.
Molex is free. The guide states I can measure the 12 and 5V rails with molex but will need the AUX for 3.3V. Realistically I could measure the 12 and 5V and call it a day, but since Im going to all the trouble it seems like a good idea to measure them all.


I take it from this snippet that I can use anything with an orange wire ?

Thanks again, I just need to be sure before I toast anything :)
Are you talking about this?


That guide you linked was made in '04, its a bit outdated. AUX connectors are usually not part of a PSU these days.

If you need help with DMM I can lend some. Its not too hard to probe these lines. You should see a percentage drop based off the rating of your PSU (Gold, Platinum, Silver, etc.). If you see too low of power, and you have already replaced the PSU, you may want to look towards the source rather than the destination.
SATA connectors get all three voltages, if you have one free.
3.3V is orange, 5V is red, 12V is yellow.
View attachment 180473

this snippet here is what particularly what I am after from the linked guide. Because of the particular problem I want to be sure that specs are met at several stages.
To be clear
You should see a percentage drop based off the rating of your PSU (Gold, Platinum, Silver, etc.)

would mean that as long as my reading for any particular rail (3.3V 5Vor 12V) is within the rating for my PSU
View attachment 180474
then my PSU is unlikely to be the culprit?

Here are the results for the 12 V and 5V rails.

12V 5V

Post 12.29 5.1

Boot 12.33 5.07/5.08

OS Startup 12.33 5.07/5.08

System at Idle 12.33 5.07/5.08

System at Load 12.31 5.08/5.09

Shutting Down 12.35 5.07

Info that I can find on my psu states that it is rated Bronze. So plugging in the numbers would look like this to me: A(rail) x 80% = lowest reading acceptable when measuring with the DMM ? Is this correct? For the 5V rail then the numbers would be (5 x .8 = 4). Then as long as I have 4V running through the 5V rail I am within spec ? I really think I am missing something

Now that I see ATM's last post I can run and check the 3.3 while you all have a good laugh at my math :) Thanks again guys


3.3V rail is rocksolid @ 3.39 throughout all stages, execpt for quick spikes to 3.4 during shutdown. and when I say quick I mean just enough time to see.
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this si the part that is immediately applicable to my situation? Thank you for the pdf BTW. I will add it to my "Things to Read WHen Google Doesnt Know the Answer" if you dont mind :)

Edit : just saw you specified a section. Sorry :)
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Google knew the answer, I searched for "ATX PSU Specification" and this was the first result. I just knew it existed already.
Sorry I got that wrong, but the fact is there will be some difference than what you expect. Let us know what you measure.
Sorry I got that wrong, but the fact is there will be some difference than what you expect. Let us know what you measure.

No harm done. Measurements are listed above and I think the psu is strong. I've moved on to blaming the OS (unless anyone thinks the numbers are not okay, and I would like to hear if they do). I feel I must have some sort of incompatibility in the packages I have installed. Progress has stalled for today though because I am also taking the opportunity to revise the OC on the system (previous was stock) and ambient temps are driving my temps too high. My workspace is on air conditioned so I will finish the OC tomorrow morning and then move the machine back to its permanent spot in a cooler climate.

Thanks for the help and links guys! Please let me know if you think of anything else I should look into while everything is torn down. I've done the usual in replacing the TIM and blowing out all the dust with compressed air, so now it's just the fun stuff left :)