2 bad PSUs, 2 bad motherboards, who is killing who?

[IAmNotLarry]

Alright guys, I'm hoping you can help me because I'm am living a PC building nightmare. There is a lot here some I'm going to dive right in starting with my problems.

At the beginning it was working...

1) Let's call this first system version A

• ■ System booted to OS and everything worked■ I started formatting my raid array and went to sleep
  ■ Problem #1 - I woke up and found the system dead. Super dead as in nothing happens at all when hitting the switch.
  ■ I ran the paperclip test and my PSU seemed fine, and my case switch worked as well so I ordered a new motherboard (after tons of other testing of course)

2) System with motherboard B

• ■ Problem #2 -Booted and got to OS for about 3 minutes before it died.
  ■ I tried paperclip testing my PSU but this time with load. I plugged in a couple hard drives with sata power connecter and the PSU clicks on and off. So, PSU A is actually dead and possibly taking other components with him.
  ■ I took a working PSU from my other computer (PSU B) and the system booted up once again.
  ■ Side tangent (you don’t have to read this): Just a side note to add to this nightmare. At home, I have two PSUs and two ATX power cables. When I use the ATX cable from PSU A on PSU A, I have to use the paperclip test to get the fan spinning. BUT they are both modular PSUs so I was testing using the ATX cable from PSU B with PSU A and the fan starts spinning even without the paperclip test pins connected. I have no idea why this is happening since ATX power cables should have the same standard pinout. I have a multimeter and as I was testing the voltage the PSU from hell finally gave up the ghost but not before I was able to read perfect voltages from the 3, 5, and 12v rails with ATX cable A and only 3 and 5v with ATX cable B. Honestly as I'm typing this I having a sickening thought. Some backstory is that I was being thrifty (read: cheap) and I bought a refurbished PSU. My thought was that their refurb testing would be super top notch because it's a refurb. But from what I’m seeing my I'm guessing that is the refurb company (probably 3rd party) added some circuitry so a half-broken PSU could limp its way out the door.
  ■ Off to the store for a new PSU let’s call it PSU C. (unfortunately the same PSU company which was the only brand-name one they had)
  ■ I wanted pause here to remind the reader that PSU B is happily booting motherboard B at this point.

3) System with motherboard B and PSU C

• ■ Problem #3 - I get my new PSU and plug everything in and....nothing. We are talking super dead again. FML
  ■ I tested the paperclip tested the new PSU and PSU C is way dead!

4) System with motherboard B and PSU B

• ■ Problem #4 - So back to my beautiful and working 1000-watt PSU B which was working before PSU C to the store but now…nothing. We are talking super dead like before.
  ■ But I tested PSU B and it’s working just fine while under load

Intermission
So, at this point it seems like PSU A killed motherboard A and PSU C killed motherboard B. The plan would be that a newly purchased motherboard C would work with my only working PSU (PSU B).

But I have tons of questions:

• ■ How likely is that?
  ■ What are the odds of two brand-name PSUs killing two brand name motherboards?
  ■ Is it possible that some other component is causing this problem?

Think about your answers before you continue reading...because the story doesn’t end here.

5) System with ... @#%^ I don’t even know anymore

• ■ I decided to see if I could get to the bios without a CPU on the motherboard (hint: you can’t) but something did happen. The motherboard turned on! It jumped into an on-for-two second off-for-two second cycle. This is what you might see if you forgot to plug in the connecter for CPU power.
  ■ This is good news so I put back in my CPU and tried again. I forgot about the CPU power cord and of course got the same motherboard power cycle.
  ■ I plug in the CPU power cord and…nothing. Back to super dead. I even took out the CPU power connecter but the motherboard did not go back to the 2 second cycle.
  ■ Side note: I think this has to do with some crazy motherboard cmos memory that I don’t understand but it doesn’t really matter since the problem seems to be related to the CPU or CPU power path

So this is where I am now. I have two bad PSUs, possibly two bad motherboards, possibly one bad CPU and a most definitely a big headache.
From what I can tell, a bad CPU is very rare and it’s likely a problem with some short on the motherboard but I’m terrified to get a third one and somehow kill it again. I tested the resistance on the 12v CPU pins to ground and they are all 5+ megaohms if that helps any technical folks.

Thoughts?

Summary: 2 dead PSUs and 2 dead motherboards and I still don’t know what’s going on. Oh, and <removed> you Corsair

<Watch the language this is a family friendly forum>

 

[IAmNotLarry]

Well... this ended up being user error due to modular power supplies. The 24-pin AIX cable from one power supply is NOT compatible with other power supplies. Just because the pinout on the motherboard is standardized doesn't mean that the pinout for the PSU matches that order. For example, one wire may be connected to 3v on the mobo and 3v on PSU A but that same pin may be connected to 12v on PSU B.