thanks again

Well time for a new PSU. And goddam me for falling for that false positive with the old MB.

Sry for all the hassle. And Thanks alot for the help!

sincerly Ben (slightly embaressed)

The CMOS clear (had it without power no batt and jumper to pin 2+3 for over 8 hours) did not work. however the lights on my usb keyboard were not flashing but stayed on. the LCD on the keyboard remained dark so did the indicator lights for caps etc.

Connected a Router to the LAN port but nothing came through, no blinking, nothing.

I am now attemting to remove Hardware in order to further locate the culprit.

I will try the LAN Port aswell.

Next thing on my list is your approach to unplug everything except RAM and CPU.

Thank you a lot for your help.

The power cord must be removed from the back of the PSU or from the wall during a battery removal clear or the power from the PSU will prevent the CMOS from clearing. 

Power is getting to your keyboard so something is happening, another useful test is attaching a LAN cable to the LAN port and a router/swtich, if the LAN LEDs light up then there is power getting to the system. Your keyboard lights are flashing however so that isn't necessary in your situation as we know power is getting to the keyboard, briefly as it may be.

the flashing lights is my usb Keyboard!

the psu was tried on my old mainboard lying next to the rig. worked fine.

yes i tried CMOS without power cable and in desperation again with power and again without power to make sure.

I would try just 1 stick of RAM, the CPU and PSU connected and test to see if that makes a difference. 

I see you have already cleared CMOS by both clear CMOS jumper and battery removal (I assume by your experience level you had the system disconnected from the power when using the battery removal method) so this is a more complex issue than simple UEFI corruption.

If the basic config fails then the next course of action is to check the individual components. Most often in situations like this it is the PSU, you say you have checked that but you did not mention how. If you used the paperclip test then that is not a definitive test method as it does not apply any real load to the PSU's rails. The only way to actually test a PSU (without expensive testing equipment) is to try it on another system. 

If you have done this and the PSU is working then I would check the CPU socket for any burn marks/bent pins. If that is all clear then try powering on the system with no RAM installed, if the system powers up and beeps (RAM missing error code) then it may be the RAM or CPU that have become faulty. If the board does not power on even without RAM installed then it is likely the board has failed, in which case you should be able to start the RMA process given the system is only a month old and should still be covered by warranty.

Let us know how it goes, good luck