Question Faulty CPU or MoBo?

May 18, 2021
Hey guys!

I decided to update my old system which was running on Xeon build with an x58 chipset motherboard. So yeah pretty old I know, that's why I bought new parts to upgrade my system.

I bought an Intel core i5-10400f (used)
a Gigabyte B560M DS3H (new)
2x 8 GB DDR4 3200Mhz Sticks

From my old setup, I am still using the
PSU Be quiet 500W
Nvidia Asus GTX 1060

Now I put everything together and the System won't even Post. No Image, no keyboard/Mouse lights. Only fans are spinning and some fan LEDs and GPU lights are on nothing else.
Now I have been trying to troubleshoot it somehow. The PSU and GPU are working as i tried them out with my old components again and it works.
I tried the build with only one ram stick in various slots. Also tried CMOS resets and tried to get it to Post with only the minimum of components (PSU, CPU, Cooler, and RAM)
Still, nothing changed, I tried starting to start it without any RAM inside to see if I get at least some beeping noise but also no beeping.

At this point, I am very sure something has to be faulty. The problem is I can't seem to troubleshoot if it's the Motherboard or if it's the CPU.

My google research led me to believe that the fault should be with the Motherboard. But the board is brand new, the CPU on the other hand isn't. Could a faulty CPU lead to the above-mentioned problem?
(No post no beeping) or would I get at least a beeping complaint from the MoBo if something with the CPU would be wrong?

PS: Just to clarify why I personally tend to think that something with the CPU is wrong is that I Bought the CPU from a big eBay seller as "New but the article has been returned and tested"

The thing that makes my inner Alarm ring is that on the CPU Box package there is an Amazon warehouse sticker and a another red sticker with "liquidation" written on it. This makes it obvious that the CPU was sold on amazon originally, someone returned it and it went back to an Amazon warehouse and then was sold on one of these liquidation websites. The eBay seller probably bought the stuff from a liquidation website and sells the stuff on eBay then. This makes me believe that there could be a chance that the CPU was returned originally to amazon because it was faulty.

Probably the best advice would be to just send both the Mobo and CPU back and order both again, but I dislike sending working stuff back, so that's why I am trying to find out which part is the faulty one so I can only send that single part back :)