Possible short on motherboard

You can look for faulty components on board with an ohmmeter on the ohm setting. Check each connection to see if there is any resistance ratings.

It may just be the power supply. That can sometimes be tested by a good computer store. Other wise the only good test is with a new power supply. That's cheaper than replacing the main board and figuring out its the power supply. And yes, the power supply can easily be replaced.

First pull cmos cell from motherbord for 10 minutes .
So all settings of bios are back to factory defaults.
Then check.
If till face problem Reconnect ATX connector to motherbord from smps.
Some times this problem occurs becasue of SMPS it is square box on back top side of cpu .
Change it then check.
Some times bord grounding problem.
So open your motherbord and check it in out side of cpu .

Let me know if you need more assistanse.
Thanks.