Question Suddenly no POST / Display, but fans work after BIOS update ?

Dec 1, 2022
Hey hey, hope you guys can help me out!

Built a new pc (kind of my first/second build) and currently I have the following problem:

The PC itself starts i.e. fans and lights turn on, however it doesn't boot /post / load into windows.
Furthermore, I now also get a red CPU light on the motherboard's error leds.

This is my setup:
  • CPU: AMD Ryzen 5 5600
  • Cooler: Cooler Master Masterliquid ML240L RGB V2
  • Motherboard: Gigabyte B550 AORUS PRO AC
  • RAM: Adata XPG Gammix D20 32 GB (2 x 16 GB) DDR4-3200 CL16 (currently only 1 built in, waiting for 2nd)
  • GPU: MSI GeForce RTX 3060 Ventus 2X 12G
  • Case: Corsair 4000D Airflow
  • Power Supply: SHARKOON SilentStorm Cool Zero 750 W 80+ Gold Fully Modular
  • and 2 additional Corsair ML120 75 CFM 120 mm Fans
  • 2 internal ssds, 1 internal hdd
  • 2 external hdds
Bought the Mobo from Amazon as "As good as new"; and used my old harddrives; other than that all items are brand new.

Steps I have taken so far and how we got here:

  • Fully assembled the pc on monday this week. It would turn on with fans etc. but not post.
  • Checked all the cables, espeically front panel etc. without luck.
  • Then I figured I need to update the BIOS as the default installed one doesn't support my processor as far as pcpartpicker told me.
  • Sucessfully updated the BIOS via USB by using the Q flash function.
Somehow it still woulnd't post and the red light for DRAM lit up, so I then simply pulled out (and back into the same slot A2) the 1 RAM stick I currently have (still waiting for 2nd one atm), and voila for some reason the pc now fully posted / booted and I got into windows. Didn't change any settings let alone went into the BIOS yet, simply tested 1 or 2 games on the pc for 30-40 minutes and thats it. The next day (tuesday) I used the pc again for around 1-2 hours and it worked fine.

NOW today however, my pc , again, wouldn't post / boot AND the red led light now displays CPU. But the fans + leds are working.

So today I tried:
  • Checking cables
  • Removing and putting ram back in
  • Clearing CMOS with the pins and the battery for more than 5 minutes each
Still nothing.

Also idk if it matters but whenever I cant fully boot etc, the front panel power button also doesn't work to shut the pc down, only to start it. But for a time it fully worked I could shut off the pc with it. Same goes for mouse & keyboard, they don't work at all / have leds while the pc doesn't get into post / windows.

Seriously wondering why the pc doesn't work now anymore as it worked on Tuesday? and am in desperate need of help haha
Any suggestions as what to do now? Hope you guys can help me out! Thanks in advance!
Last edited:
Dec 1, 2022
Unplug the external hd's and the internal hd,as long as it is not the os drive, then try to post. Any change?
Thanks for the reply & suggestion! Tried it with only the os ssd, but still won't post and solid red cpu light on the motherboard is still there too. So unfortunately no change : /
Dec 1, 2022
Update: Reseated the CPU + AIO cooler, thought maybe that might help, but still no post and red cpu light.

AIO Cooler plate has very small scratches btw
Yes, but I assume/hope not much. At least that's what I understand under "as good as new".

Regardless what really wonders me is that the whole thing worked for a bit but now it doesn't anymore
Yes you would have to wonder why it was returned. Makes sense that if they tested it it worked for them, but it probably did the same thing for the first owner working intermittently would be a good asumption. The only thing I can suggest is to check the cpu very closely for any bent pins
Dec 1, 2022
SOVLED the problem.

Update for anyone having the same problem:

Spent some more hours troubleshooting but couldn't get the pc to properly work.

So I looked for a repair store and gave my pc in for inspection repair beginning of december.

The folks there were extremely nice and quick as well, literally got a call 2 hours later (right before their closing time) from them saying they found the issue.

The issue was that my mainboard was broken and simply didn't recognise any CPU at all.

So while my pc was at the repair shop anyway and they sold hardware too, I asked if they have any similar motherboards available that they could install for me & i could buy off of them.

So, not even 24 hours later, I got a new motherboard installed and now ever since everything works perfectly. Been using my pc for over a month without any problems now.

Got the Asus ROG Strix B450-F Gaming 2 as my motherboard now. Sent the broken one back and got it refunded.
Reactions: Ragnarok17