No POST, no beep, but CPU fan spins…

Yes, another one of these threads, and unfortunately this time it’s happened to me.
I swapped out my CPU for a new one, nothing else has changed. I get no video (either through the card, or the on-board), no beep, no hard drive spinup. Yet the CPU fan does spin.
Does the fan spinning bear any relation to whether I got a dud CPU? I’m considering swapping back to the old one, but obviously I don’t want the effort and thermal paste if it’s something else.
Tried unplugging everything that isn’t necessary, tried swapping memory, tried BIOS reset.
And yes my mobo does support the CPU
Answer #1
well put the old cpu in. if it works then it might be the cpu .
Answer #2
Sprang to do that, turns out it was the CPU. No idea why. I’ll probably RMA it and get a new one.
Answer #3

And yes my mobo does support the CPU
You verified this on the manufacturer site by looking
at the supported CPU list? Was your bios version same or newer then the one supporting this particular CPU?
Did you disconnect the 4PIN plug near the CPU socket?
If so put it back in.
Edit: I see i posted only a few moments after you,Guess it doesn’t
matter now.