Possible causes for motherboard can't reach POST mode other than a faulty RAM

samudera38

Prominent
Jan 4, 2018
3
0
510
Hi and good day. Just a quick question.

Consider a new build PC (just finished assembling) can't past POST mode, with the fans and power light are working.
If the RAM is removed, the mobo speaker produces long beep in 3 consecutive order (should means that the mobo detected no ram slotted).
What would be the possible causes of this problem other than a faulty RAM?

Case in hand:

CPU: Intel i3-8100
Mobo: Asrock Z370M Pro4
RAM: Single Crucial 4GB DDR4 2400mhz
PSU: Corsair VS450
No VGA card, no storage drive.

It would be great if the possible causes would be in the order of the most likely to happen first.

Sorry for the bad English. Thanks in advance!

*Edit: All components are brand new.