Suspected Motherboard DOA No POST. Lights+fans work, CPU LED on. Have followed “PERFORM THESE STEPS before posting about POST”

Mar 11, 2018
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I purchased the following components to upgrade my desktop:

Intel i5 8400
Gigabyte Z370 Aorus Ultra Gaming
Corsair Vengeance 16GB (2x8GB) DDR4 3000 LPX

However when I put them together it will not POST. All of the fans and lights come on (as does the CPU debug LED) for a few seconds, cuts out (turns off). This then repeats for a second time and then does not come back on. There are no beeps from the internal speaker at all and it cannot be turned off using the power switch (or headers) only but switching off the PSU.

I have tried breadboarding the setup with only the components above (with only one RAM module) plus the internal speaker and the results are exactly the same.

I have also tried with no RAM installed and still exactly the same (no beep codes, cpu led on and the two time loop described above)

I have gone through steps 1-23 on the “PERFORM THESE STEPS before posting about POST/boot/no video problems!” guide several times to no avail (NOT INCLUDING the section beginning “If you suspect the PSU is causing your problems...”). I have ruled out a PSU issue as it successfully POSTs with my old CPU, motherboard and RAM (and GPU).

This is not my first build and I have never had issues like this before (only ones that were solved with much less troubleshooting than this!).

From this the problem must lie with either the CPU or motherboard, with the motherboard being the most likely culprit (I believe?).

Video of POST attempt.

Complete System Build.

So RMA the MB; unless anyone can think of something I haven’t?