Question Motherboard flashing on new build and not turning on. Changed motherboard, same issue.

Dec 30, 2022
Hi all,

Apologies if this will be a long post but I don't know what else to do and I'm getting desperate at this point.

A couple of weeks ago I built a new PC with this setup:
Here’s the full list:
CPU: Intel i5 13600K
GPU: Gygabite Aorus RTX 3070
PSU: Corsair RM1000x
RAM: 2x Kingston Fury 16GB DDR5 5200 MHz
CPU Cooler: Corsair iCue H115i RGB Pro XT
Motherboard: Gigabyte Z690 Aorus elite AX (DDR5)
Storage: WD black SN750

The thermal paste I used is Noctua Nt-H1.

I start building the system out of the case and I'm ready to do the flash bios needed by the Z690 to run a 13th gen processor. I connect everything, everything lights up (RGB on motherboard and GPU lights/fans), and I do the bios update with the straightforward bios flashback. All seems to be working fine, so when it all ends, I try to turn on the system and get it to boot. The system runs for 5 seconds, and then turns off. Since then, it doesn't turn on anymore at all, basically, the motherboard's led flash for half a second, but that's all that happens when I turn on the PSU.

I searched for solution/fixes and eveybody told me that unfortunately I had bricked the motherboard. I tried a few things, such as removing the CMOS battery, but didn't work. So annoying. I send it back and order a new one. However, since I didn't want to risk it again, I upgraded to a Z790, so I don't need the BIOS update anymore.
Today it finally arrived, I connected it all again to test it and...same exact issue, with the new motherboard.
Since then I have been trying to troubleshoot it and understand what is not working. Below a few tries I made, by each component.

PSU: Tested the fan connecting the two pins, all working. Also tested the whole system with my old PSU (RM1000, not RM1000x), same exact result. Checked all cable multiple times, connected the CPU fan from the AIO cooler.
Storage: tried to remove the WD SN750 and boot the system without any storage.
AIO Cooler: tried to tighten a bit the screws. Tried to remove the cooler, remove the old paste, clean it all and put new paste, covering it well and put it back.
RAM: removed one stick at the time. Changed channes, both with one or two sticks. Tried to boot with no sticks at all.
CPU: Checked all pins. Tried to connect the motherboard without CPU, just to see if the LED went back to be fully on.
Motherboard: Checked that there are no shorts, every screw is tightened in the correct way. Changed the material I was building the pc on to check for static electricity.
Power outlet: Changed the power outlet I was connecting the PSU to.

Nothing of this worked. In any combination above, still a superquick led flash, and that's it. the first time I power the PSU the flash is a bit pink, subsequent times instead stays always red.
Now, all the pieces are new and think we can exclude the motherboard being the issues, as I got a complete new one and this time around the was no Bios Update. What could be? I feel I only have the CPU or both stick of RAM malfunctioning as options, but wouldn't the motherboard at least have the led going on withouth them (one at the time)?

I'm happy to try and send back the CPU/RAM too after the motherboard, but I would like some advice before doing that, especially because it feels it might not really make a difference? Please help, I really do not know what else to do and I'm currently very frustrated after all these efforts.

Thank you!