Any component may fail, even the front panel. Unplug all cables. Clear CMOS. Plug in required components only: 1 RAM module and power cables.
Thank you @karlmistelberger. I am in the process of dismantling everything, no time like the present for a good cleaning. Do you think I should reinstall Tumble weed as well, after I get things working?
Needed to do some thorough cleaning two years ago.
I don’t think so. btrfs is very robust. It survived the mishap without any damage:
erlangen:~ # stat /
File: /
Size: 452 Blocks: 0 IO Block: 4096 directory
Device: 0,38 Inode: 256 Links: 1
Access: (0555/dr-xr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2025-12-06 04:54:45.962965266 +0100
Modify: 2025-10-04 05:56:14.111764822 +0200
Change: 2025-10-04 05:56:14.111764822 +0200
Birth: 2021-11-24 21:33:32.572006306 +0100
erlangen:~ #
I created the filesystem when buying a big drive in November 2021 and never experienced any trouble:
erlangen:~ # fdl /dev/nvme0n1
Disk /dev/nvme0n1: 1.82 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: Samsung SSD 990 EVO 2TB
Disklabel type: gpt
Disk identifier: 9CC8F3A2-0DC2-4237-8673-D76DCF8AF37F
Device Size Type
/dev/nvme0n1p1 100M EFI System
/dev/nvme0n1p2 1.8T Linux filesystem
erlangen:~ #
Further to the on going problem. I did dismantle and reset everything in the PC, including resetting the CMOS, as per link given by karlmistelberger [thank you]
It took a little while as I had sent my PSU back. I installed the new PSU and bare components only. Now the PC powers up fans and lights, still no POST or beeps and then after 15 seconds all the fans stop and the red [CPU] QLED flashes momentarily, then goes out and the amber [DRAM] QLED stays on a little longer and then goes out. The eye candy lights on the m/board and the interior Power switch light stays on until I turn the power supply off.
Not sure what causes the fans to stop. There are 3 case fans and the CPU fan.
@LaQuirrELL that’s likely a motherboard fail safe to power down…
thank you malcolmlewis
Since I have no GPU and the PSU is just new and I have put in a new on/off switch, that would leave only the RAM or the M/Board in question?
Is there a way to test the RAM?
@LaQuirrELL Only in another system that you know works…
When you say no GPU, you mean a discrete one rather than one integrated into the CPU?
Yes, we are using onboard sound and graphics only.
Try a minimal system with no case, no USB, no SSD, no HDD, CPU fan only, a single RAM module only. Even a bad battery on the main board may cause the trouble.
Try reseating the CPU. Your memory controller is in the CPU and if a little heatsink compound got on the pins it could cause problems at any time.
My only other thought besides the PS or a component/solder/trace failure on the board is a corrupt BIOS. You can put a BIOS file on a USB stick and it’ll flash the BIOS at power on.
That’s a last resort though, once you’re convinced nothing else will fix it. My old machine just went stupid and clearing CMOS didn’t help. Wouldn’t post or it had error beeps, but it wasn’t consistent and would change with each try to boot.
I have no clue what caused it, possibly a power outage while it was in sleep mode? Using a USB stick to flash the BIOS at power on fixed it. That was an ASRock board that was made by Asus. I didn’t try reseating the CPU because I knew it was installed correctly and clean, and had worked fine for years.
Good luck.
Try a minimal system with no case, no USB, no SSD, no HDD, CPU fan only, a single RAM module only
Unplugged everything except 1 RAM, CPU and CPU fan. Made sure the RAM was in the right slot.
Result - The PC powers up CPU fan and lights, still no POST or beeps and then the red [CPU] QLED flashes momentarily, then goes out and the amber [DRAM] QLED stays on a little longer and then goes out, after 15 seconds the CPU fan stopped. The monitor states - No signal. The eye candy lights on the m/board and the interior Power switch light stays on until I turn the power supply off.
Originally I had tested the CMOS battery and it was testing good, but because you mentioned battery, I replaced it.
Results were the same as above.
Thank you jsmith64.
You can put a BIOS file on a USB stick and it’ll flash the BIOS at power on.
I did reseat the CPU as suggested, checking for dirt grease etc., it was all good, but did not make a diiference in the on going problem [No POST, no beeps].
I have been in touch with Asus in regard to flashing the BIOS [without on screen access to BIOS], I would need a USB BIOS flash port on the m/board. The Asus Prime Z390A has no such port.
Would you maintain that I can flash the BIOS from any USB port at power on?
From the user guide:
"MemOK! II switch (MemOK!_II)
Installing DIMMs that are not compatible with the motherboard may cause system
boot failure. The switch is enabled by default, allowing memory re-training when the
motherboard is unresponsive due to memory problems. The Mem_LED will light up
while re-training, and turn off when the re-training is complete"
Thank you, karlmistelberger. The RAM I have is the original RAM that came off the QVL for this board. It has been installed since 2019 when the PC was built. Kingston HyperX Predator 32 GB x2.
More hints from this section:
1-10 Chapter 1: Product Introduction
Chapter 1
• Refer to section 1.1.8 Onboard LEDs for the exact location of the Mem_LED.
• The DRAM LED also lights up when the DIMM is not properly installed. Turn off the
system and reinstall the DIMM before using the MemOK! II function.
• The MemOK! II switch does not function under Windows® OS environment.
• During the tuning process, the system loads and tests pretest profiles. It takes about
30 seconds for the system to test one set of profiles. If the test fails, the system
reboots and tests the next set of profiles. The system will reboot multiple times when
training, once the system has completed the training process the Mem_LED will turn
off, please refrain from doing anything before the Mem_LED turns off.
• Due to memory tuning requirement, the system automatically reboots when each
profile is tested.
• If you turn off the computer and replace DIMMs during the tuning process, the system
continues memory tuning after turning on the computer. To stop memory tuning, turn
off the computer and unplug the power cord for about 5–10 seconds, then set the
MemOK! II switch to disabled.
• Ensure to replace the DIMMs with ones recommended in the Memory QVL (Qualified
Vendors Lists) at www.asus.com.
• We recommend that you download and update to the latest BIOS version from
www.asus.com after using the MemOK! II function.
Newer boards, e.g. the Micro-Star B550-A PRO are Plug & Play. The ASUS PRIME Z390-A is pretty old and needs some hand holding.
According to the Prime Z390-A specs at the Asus site, your board has ASUS CrashFree BIOS 3.
I hate to say Asus is wrong, but Crash Free BIOS 3 is specifically for fixing a corrupt BIOS.
Instructions are:
Recovery Media: You’ll need a USB flash drive (FAT16/32 formatted) containing the correct BIOS file in the root directory (renamed as per ASUS instructions).
Download the latest BIOS for your specific model from the ASUS website, extract it, and use the ASUS BIOS Renamer tool (found in the folder) to rename the .CAP file. Yours is PRIME Z390-A BIOS 2101 Version 2101 8.48 MB 2024/03/05.
I just rename BIOS files in the file manager. I think they use the renamer tool because it’ll flash it at boot with the USB stick plugged in whether you want it to or not.
Recovery Process: Insert the USB stick, restart the PC, and the system will automatically find and begin flashing the BIOS from the USB stick.
Completion: A message will confirm success, and the system will reboot, after which you can press F1 to enter setup and load defaults (F5) if needed.
This guy says his would not flash so he used a USB EPROM programmer that clips onto the chip while it’s still on the motherboard. He said it fixed it. I looked up the programmer and it’s $10 (CH341A EEPROM BIOS Programmer .
Help unbricking bios - Asus Prime z390
Keep in mind that the board could be dead forever but $10 isn’t a lot to spend to try to save it. And make sure you remove the battery and switch off the PS (or unplug the machine) when you clear the BIOS. Also, press the power button while doing this to drain any residual power. If you’ve done that, then it didn’t work. Try flashing it.
According to the manual the above post contains several incorrect informations.
The recovery tool Crash Free BIOS 3 will not automatically flash/recover the BIOS. When it starts, it will open the ASUS EZ flash 3 tool which requires a working display.
Additionally, a bricked BIOS without any attempts of flashing it is really unlikely. I wouldn’t spent much more time into this direction.
I’m confused by the inconsistent sequence. The manual states this:
- One short beep: VGA detected, Quick boot set to disabled, No keyboard detected
- One continuous beep followed by two short beeps then a pause (repeated): No memory detected
- One continuous beep followed by three short beeps No VGA detected
- One continuous beep followed by four short beeps: Hardware component failure
A few days back in this post, you mentioned 3 beeps, why is that not happening anymore? If it’s 3 short beeps then it could be a graphics problem.
Also you mentioned memory training, but did you check the position of the MeMOK! switch as quoted by karlmistelberger above? Those details are important.
Thank you opsusemaco.
Yes at one time I did hear three beeps, one time only. Also, just after that I did hear one beep, one time only. All other subsequent times at powering on there were no beeps. I do not have a discrete graphics card installed, only using onboard graphics.
I got quite enthused when I heard these beeps, but they never reoccurred.
The MeMOK! button is in the on position, has always been in the ON position.
Thank you hui, for getting that information re: BIOS flashing. When I clicked on the pdf link it opened a new tab and said “Access denied”, so I could not look at it. I do have a user guide for the Z390A and it does explain the Crash Free BIOS 3.