Problem with PSU, CPU or Motherboard - pc fans keep spinning after shutdown

madsemil

Prominent
Feb 19, 2017
2
0
510
I recently build a new system with the following specs:
cpu: i7-7700
psu: evga 550 g3
MB: msi-z270-a-pro
ram: cosair vengeance 4x4 gb
ssd: intel 600p m2
(no graphics card atm)

The problem:
Whenever i turn on the PSU by using the on/off switch on the back of the PSU, the CPU-fan and the rest of the case-coolers starts to spin. At the same time the CPU debug-led on my motherboard lights up (notice there are four debug-leds - cpu, dram, vga and boot - and only the cpu-light is on).

Details:
I can perfectly fine boot into windows by using the case on/off switch, but when i turn off the pc, the fans keeps spinning and the debug-led lights up again (the debug-led on the motherboard turns off, when i turn on the pc). The only way i can make the fans stop spinning is by turning off the PSU, thus removing the power.
The PC recognizes both the ram and the CPU.

What i have tried so far:
- I have tried running my system with an older PSU (corsair 700 gs). When i do this, everything is running fine - the fans stop spinning, when i turn off my PC. Also the CPU debug-led is off.
- I have tried using the new PSU on an older system with an Asus P8Z68-V motherboard. Everything works fine and there are no problems.
- No pins on the CPU are broken.
- I have checked that all connections are properly connected - especially the front case-connectors, including the case-switch.
- I have updated bios and all drivers (even though it seems like, it is not a software problem)
- (i do not have a case speaker at the moment, so i cant hear any beeps, but i am looking to get one as soon as possibly)
- I have tested the ram sticks and there does not seem to be a problem with the ram - also, the PC boots fine.
- I have tried various settings in the bios.
- I have tried resetting the cmos.
- Problem persists when i try to shut down in safe mode.

It seems like the motherboard (msi-z270-a-pro) and the power supply (evga g3 550) are incompatible - but is that even possible?

Does anyone have a solution to this problem?
Does anyone know how i can further test my system and figure out what part is malfunctioning?

Kind regards
 
Yes, okay i thought so, but then how can i figure out whether it is the motherboard or the psu that are causing the problem?
I don't want to send my PSU or MB to RMA and then have to pay the distributor for troubleshooting, because they cant recognize the problem.