Question Asus ROG Strix B450-F won't boot but LED on I/O shield is on

Feb 2, 2021
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I built a custom PC following the manuals instructions and it worked. After some months, sometimes the PC didn't turn on when I pressed the power button. Then I tried again and again and the PC started. Currently it is very difficult to boot my PC and I chose don't turn it off and it stays on. But this is not a solution for me and I need to know what is wrong to fix. I want to turn off my computer and turn it on later when I press the power button.

Nowadays, when I switch on the PSU the ROG LED light on the I/O shield of the motherboard turns on. The Q LEDs (CPU, DRAM, VGA, BOOT) don't light on, meaning that these components are OK. But, when I press the power button, nothing happens. The computer doesn't start, even using a paperclip in pins of the motherboard.

There isn't a reproducible way to turn on the PC. Sometimes I wait some hours and press the power button. Other times I need to get off the battery and put it on again. And others I remove and put again a video card or other parts. When I can turn on the PC, almost all the times the BIOS date/time is wrong.

My hypothesis is that the motherboard has some problem with the battery or CMOS.

Tests that was made

  • I took the PC to technical assistance and they checked all parts and each component (PSU, cables, motherboard, CPU, memory, SSD, battery, fans and others) are fine.
  • I disassembled and assembled all computer 2x
  • I replaced CMOS battery 2x to new one
  • I used a multimeter to check battery, cables, PSU and socket power from wall
  • I replaced the metal screws to plastic screws to attach the motherboard in the case
  • I cleared CMOS
  • I replaced the power button
  • I used a screwdriver to turn on direct on pins of motherboard
  • I followed many checklist to test and to assembly the computer
  • I read dozens of posts about problems like mine
  • I set APM on BIOS to automatic start PC at 7:30 AM (its works sometimes)
After all the tests I can't figure out what is wrong.

Why does my PC sometimes doesn't start?
Why is the BIOS's date/time wrong after a long period of time (1 or 2 days) turned off if the battery is new?

PC specs

MOTHERBOARD

ROG STRIX B450-F GAMING (Rev 1.xx)
Chipset: AMD Ryzen SOC (Rev. 00)
Southbridge: ADM B450 (Rev. 51)
LPCIO: ITE IT8665
BIOS
Brand: American Megatrends Inc.
Version: 3103 - AMD AGESA Combo-AM4 1.0.0.6
Date: 06/17/2020
CPU
AMD Ryzen 5 2600
MEMORY
16GB (2x8GB) Corsair Vengeance
VIDEO CARD
Name: Radeon RX 580
Revision: E7
Memory: 8 GB
Type: GDDR5
PSU
Corsair CX750
Disks
2x Corsair Force Series MP510 480GB NVMe PCIe Gen3 x4 M.2 SSD (connected with RAID-0)
1x SSD Kingston 120GB
 
Feb 2, 2021
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"I used a screwdriver to turn on direct on pins of motherboard"
What happened when you did this?

Have you tried to jump JUST the PSU....like this...
http://support.antec.com/support/solutions/articles/1000015319-is-my-power-supply-dead-the-paperclip-test
If so....what happened?
When I used a screwdriver to turn on direct on pins of motherboard, one or two times worked and PC started.
I tested only the PSU using a paperclip and the fan worked. I used a multimeter to test the voltage and everything is right.
 
Feb 2, 2021
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UPDATING

My computer still turned on for some days, when it turned off automatically 30 minutes after I started a game. After that, I tried to turn it on using the power button, but it didn't work. The next day, I disassembled the computer and executed the bare system testing. At this time, the Qcode led didn't turn on when I tried to turn on the computer with only the motherboard, PSU and CPU. I expected that the Qcode light for memory or VGA turned on, meaning that components are missing.

So, I decided to take the computer to technical assistance to determine what component is bad for replacing it. For my surprise, they turned on my computer without replacing any component.

The technician told me that the motherboard was in protective mode and to get out of this state, he put only the motherboard above an aluminum paper for about 1 minute. I know this is a homemade solution, but it worked.

I read all of the motherboard's manual and searched in the internet and didn't find anything about "protective mode", so I suspect that the motherboard stayed in short circuit or some component like capacitor is missfuncting, and the fact of putting it above an aluminum paper stabilized the circuits.

Now my computer stays turned on and I am afraid that, after turning it off using the power button, I will couldn't turn it on. If this happens, I will try to use the aluminum paper again, but I know this is not the best practice. So, what do you recommend to do in this case? There is really a protective mode in the motherboard that prevents it from turning it on? How to prevent that from happening again?
 

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