No Power Signal on PC, Tried Jumper & Changing Hardware

I had an old AMD processor and mobo with 2 sticks of DDR2 RAM. One day all of a sudden everything went blank, and it said no power signal.

With that system I tried holding power button for 1 minute or so.
Tried CMOS jumper resetting.
Tried, BIOS reset with battery removal/change.
Changing RAM Slots, Running PC with only One RAM and every other possibility.
Tried replacing PSU.
Nothing worked and I gave up.

Now slowly, U upgraded everything from PSU, CPU, Motherbaord, and RAM to newer parts. But still I am getting no power signal.

With new system also, I tried everything I have mentioned above. What could be causing all this? I have built at least 15 PC before, and never such issues have arise.

PLEASE HELP ASAP!!! THANKS IN ADVANCE!