Where are you measuring no 12 volts?  At the 24 pin connector? And the CPU power connector?  And the GPU power connector?  And the 4-pin molex connector?  Or, are you only measuring one of them?  If you have measured only one of those places, how about measuring the other 3 places?
 
What are you using to measure the voltage when determining that there is "no 12v"?

How exactly are you measuring and where? Ty_ger07 is right. We will need more info to see what is happening with your system.
Of course I am also assuming that your system is not turning on because of this.

As far as testing I did all that with the old PSU, so I just replaced it with anew one same problem.My PSU is Corsair 850x. I'm really tired of hitting a brick wall, If some around L.B. I'll bring it you to see what you can do. By the it's on a test bench, and tried on a box same thing.

flasher4q
As far as testing I did all that with the old PSU, so I just replaced it with anew one same problem.My PSU is Corsair 850x. I'm really tired of hitting a brick wall, If some around L.B. I'll bring it you to see what you can do. By the it's on a test bench, and tried on a box same thing.

Still zero useful information.  WHERE are you trying to measure for 12 volts?  WHERE have you failed to measure for 12 volts (where you probably should have also measured)?  WHAT are you using to measure for 12 volts?  HOW are you performing your measurements?  Do you know how to use the tool which you are using?  Have you successfully used the tool before?  Can you verify that the tool is working properly and giving you a proper reading? Is the computer even being tested in a way that 12v is to be expected at that point, or is there some other issue you have failed to consider which explains why it would be normal for the PSU to detect a fault and not provide 12 volts?
 
12 volts missing on 2 different power supplies is.... pretty much unbelievable.

If you want someone to help you, you need to give more information. Tell us a story. As it is, with only 4 sentences, the possibilities are too endless.

The hardest error to solve is an error caused by lack of knowledge. If you don't know what you don't know, you can't detect and correct for it on your own. So, you have to give us a full explanation so that one of us can maybe figure out what is wrong.


My computer won't turn on. I press the power button, but nothing happens.
Paragraphs of possible solutions from others.
Well, there has been a blackout in my area for 6 days. Do you think that is relevant?