Computer in power on/power off loop, PSU is suspect, how to properly test

So for the last few days I have been having computer trouble with a persistent power on/power off loop. My computer never fails to start up, it either goes through a boot loop or remains on and never posts. I created a thread in the motherboard section and right now I have deduced that it is either the power supply, motherboard, or both are the culprits. I've tried resetting the bios to no avail, and what has made it possible for the computer to post is removing a stick of ram, however sticks of ram that I tested that were good, are now giving me trouble.

So with all that being said the PSU in question is a 2013 non-modular Corsair CX 600 and it is 80 plus bronze. I want to know what is the best and most accurate way to test my PSU. So far I have tested the PSU using the paper clip method, tripping the green power wire with a black ground. I also tested the various voltages on the wires with a multi-meter, all seemed to be fine and well within their voltage ratings, which includes the +/- 5% and +/-10% discrepancies. I think the only wire that concerned me was the blue wire which is supposed to be rated at -12v but read as -11.30, which is still well within 10% but that is the only one that I found somewhat questionable.

So I realize that this test is only testing the power supply when it is not under load, is there any way to test the power supply under load and get an accurate reading of the power being drawn from it? If I can get my PC to post again, would there be any utility I could download for windows that could monitor this? Please lend me your knowledge and advice. Thank you.

You'll need some beefy resistors or equipment designed to simulate DC loads, and measure the loaded drop. if it's outside of 5% or so, then ya PSU is shoddy or borked.

you can also just try whacking it into a less power hungry system

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So from what I researched the the +/- 12v rails all allow for discrepancies of +/- 10%, or is that not the case? Did I receive bad information?

Also where would I obtain resistors and would you give an example as equipment I could use other than my multi-meter. I've got a few engineering friends that might be able to help me out.

iirc the 80+ standard only allows for 5% fluctuation under load. As for the Equipment: you'll need a dummy load, or modular DC electronic load, for the cheap route, just google "power resistors" or "high power resistors" to find ones that will cause a decent voltage drop (look for like, 8-20 Ohm, 50-100W spec) and gator clip em across the rail you want to test.

after a quick google I found a video of a guy doing exactly what I'm describing here:

Chances are the cheapest solution will be to order a new PSU (from seasonic if you want quality) throw it in the system, and see if it boots. if it does, RMA or toss the old one, and if it doesn't return the new one and whatever part you determine to be faulty.

11.3v unloaded sounds pretty darn low unless your PSU is doing some weird voodoo for voltage regulation.

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Based on what you said the blue wire that read -11.30v is well over a 5 percent discrepancy then. -11.40 would just be hitting that 5 percent threshold. Hmm based on that I'm guessing it really is the power supply then. I did more research and apparently the CX 600 is one of the bottom tier power supplies, so there you go. Now another question, if would so kindly answer, what excatly does the blue wire supply power to, would that much in power fluctuation cause motherboard issues such as not being able to supply power to parts of the motherboard? Thank you for the video btw, wasn't exactly sure should have been looking for.

Blue is -12v rail, not 12v. measure the yellow wire for 12v rail. here's the full pinout of the 20+4 pin connector:

If I may be so bold, you may want to look at buying a seasonic m12II 620 as replacement. great price for a well built modular PSU.

I know that the blue is a -12v rail as stated in my original post, I even said that it was reading -11.30v. My current question now is what does the -12v rail (blue wire) supply power to? Could that be giving me issues with my motherboard not accepting RAM or creating the power on power off loops? Also the yellow wires all check out, they're just a bit over 12v, which is fine.

Thank you for the PSU recommendation.

crap, I meant the s12II, not the m12II typos man...

iirc the -5v rail was for the Ram and ISA bus and -12v was for PCI and Rs232. no idea what they're used for nowadays, but it may just be a legacy requirement for the atx standard.

Thanks for the feedback and recommendations.