My system wont boot and has no made no beep sounds or lights flashing

[au-decl]

Without warning my system wouldnt turn on even though i had used it previously that day and it worked fine.ive tested all the parts and they all work except for the cpu and motherboard. Iwhen i had just the ram and cpu in, i put in the 24 pin and the power supply fan started but when i thn plgged the 8 pin cpu power in the power supply fan wouldnt start and the cpu wouldnt heat up. I then i then put the sames cpu into a known to be working motherboard of the same model to my non working one and with the 24 pin and 8 pin cables plugged in it started up and the cpu heated up but didnt post. In this process the gpu and power supply fans both spun up and stayed on. I then put the known to be working cpu back in the working motherboard with the working system and it didnt post. Neither of the cpus had bent or damaged pins and the voltages coming out of the 24 pin and 8 pin cables were normal from both power supplies (which are also both identical corsair vs550's). All the parts in both systems are less than a year old and are still covered under warranty.

I need help to know what the specific problems are and whether there is a solution or if i need to send either of these parts back

 

[CBender]

Your mobo probably gave up and decided to take the cpu for the ride. It is common to lose both cpu and mobo when mobo has a critical failure. The fact that in the other system the cpu is more responsive indicates that also your motherboard has issues. Just to be on the safe side, try the second power supply to your 'broken' rig. It could be a power issue also you would be more sure that the motherboard is also dead.