Today I got my new PSU from UPS. I reassembled my computer. Now when I hit the power button, the power supply's blue LED flashes for a brief moment, but nothing happens.
I did the paper clip test on the PSU and it passes, so thats not the problem.
Now I think its my motherboard. I did a different test to see if it was actually the motherboard. I plugged my 20+4 pin connector to the motherboard, and the 4 pin next to my CPU. I then used a screwdriver on the power switch pins to short and kick my PSU on. The same thing happens that I said at the beginning, the blue LED in my power supply will come on for a brief moment and then shut off.
While doing this, I accidentally bumped another one of the pins with my arm and felt current going in, so my PSU light flashing and the current I felt confirms the board is getting power. Now its about locating the short (if there is one,) or testing another power supply. Ive done a smell test for burning, and visual inspection for burning and faulty capacitors and the board checks out. I am not an expert and this leaves me all out of ideas.
How many watts is the PSU?
What motherboard model number?
Did you have ram inserted?
Is there a CPU in the socket and is there a CPU fan connected?
Is there thermal paste between the heat sink and the CPU?
I have run into the same problem about 4 months ago.(The model is Seasonic S12II 330W) Both the problem and the test way are exactly the same with yours. I have tried to put it into my another computer, but it still doesn't work. So I just message the seller,and them let me return the PSU directly. After few days,they back to me a new one.
Now review this problem,seems there were some fails on the function of overload protection in that time. If you disconnect all the components. PSU will work fine. but just need some loads, the problem will come again. Perhaps you can make further test by adding some light loads to it, like CD-ROM.
But under this conditions, I think you can call your seller without any hesitation.
I was watching a stream and my computer just shut off entirely at random. This was due to my PSU dying. I have a new PSU but it almost seems like my motherboard has a short somewhere but I cant locate it. All of the capacitors check out so I know its not them.