Question PC suddenly won't boot

Nov 13, 2022
Hi guys. Could you help me figure out why my PC all of the sudden refuses to boot?

The system is just a few months old. The mobo is an asus rog strix b550-f wifi ii while the CPU a ryzen 5 5600G with at present no dedicated gpu (i'm waiting for prices to drop a little)

It used to work just fine until yesterday when i turned it on and this happens:

  • while off there is the rog led on the mobo blinking as usual
  • after pressing the power button only the cpu fan starts spinning while chassis fan and leds are not working, RAM leds work, mouse docking station leds work
  • the leds for diagnosis on the motherboard turn on like this:

  • - it flashes briefly and just once orange the DRAM led
  • - it flashes once red the CPU led
  • - it turns and keeps on white VGA led
  • - it turns and stays on a greenesh BOOT led
I tried to reseat every single component and cable. I didn't notice any damage or dirt, didn't smell any burnt.
I've assembled a dozen of rigs for me, family, friends and i swear i've never been so confused.

Since not even the chassis fans and leds are working my bet is on either the mobo or the PSU but maybe i am missing something? Any suggestion?

Edit: update with full system specs

Mobo: asus rog strix b550-f wifi ii
CPU: Ryzen 5 5600G
PSU: EVGA supernova 750 G6, 80+ gold, fully modular
SSD: WD Black SN850 nmve
RAM: Corsair vengeance rgb 2 x 16gb DDR4 3200MHz c16

Heat sink: cooler master hyper h412r
Chassis: cooler master cosmos c700p

Other peripherals i've used on this pc
Mouse: razer viper ultimate
Keyboard: my old Ttesport mechanical keyboard, can't remember the name
Monitor: samsung odyssey g5
Headset: logitech g933 artemis spectrum
Speakers: logitech z623

OS: windows 11 pro
Last edited:


Update your post to include full system hardware specs and OS information.

Include specs for PSU, disk drive(s), and other attached peripherals.

Are you able to access BIOS?

Try a new CMOS battery as a matter of elimination.

Any beep codes?

Will the PC boot into Safe Mode?

Do you have access to another known working PSU that can be swapped in? (Remember: do not mix and match cables between modular PSUs.)
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Nov 13, 2022
Original post updated with full system specs

I'm not able to access bios at all
Can the cmos battery prevent the system to boot at all? I'll get one and try to replace it anyway.
No beeps at all.
The pc won't start at all.

I've got my old pc, from which i'm writing right now with a working psu (a cooler master 850 gold v2, also fully modular) I'll try to swap the psu and all the cables


CMOS battery - FYI: key components,-oxide-semiconductor) chip.

You can easily find other, similar links with additional information and details.

Even though the batteries may be expected to last for some time that can no longer be taken for granted.

Like many other products, the battery was probably constructed as cheaply as possible with little or no manufacturing QA (Quality Assurance).

Fortunately the batteries remain somewhat inexpensive and easy to replace. Even if to simply eliminate a potential culprit.
Nov 13, 2022
CMOS battery crossed out of the list. I've just replaced it but got the same result.

When i'm done working or at the latest tomorrow i'll try to swap the psu.
Nov 13, 2022
So, i swapped the PSU with my old computer (every single cable) and the new pc behaves the same.

CPU fan spinning when i press the power button. RAM leds on, no sign of life from chassis fans. Mobo goes through the same led sequence and stays with the white VGA led and green BOOT led on.
Nothing on screen, no access to BIOS or anything.

I then borrowed from the old pc the gtx 970 and even with the graphics card in, same outcome.