Question Motherboard light blinking even the power was off.

[Cimexl]

I'm helping a friend's PC. It's using an Asrock Steel Legend B450 motherboard. The motherboard light blinks on its own even when the power cable isn't plugged in. When the power cable is plugged in and turned on, the PC won't start. I've already tried resetting it with a jumper, but it still doesn't work. Initially, the PC got stuck in Windows recovery, and after forcing a shutdown, this issue occurred.
I've test everything, gpu, ssd, ram everything is normal.

 

[helpstar]

unplug hard drive and try getting into bios
plug in all cords/plugs

 

[Cimexl]

I cant get to the bios, the pc just won't turn on. Everytime i plug everything and press the power, it just keep blinking.
https://drive.google.com/file/d/1BhezEBvZzCs8H46CIcRz_53zfMV6NO2h/view?usp=drivesdk

 

[Eugene$$]

Could be a dead mobo, you need aother mobo to test, psu works?

 

[Dashhh]

With that board being potentially dead, how were you able to test all of the components? Do you have another board to test with?

 

[CountMike]

I'm helping a friend's PC. It's using an Asrock Steel Legend B450 motherboard. The motherboard light blinks on its own even when the power cable isn't plugged in. When the power cable is plugged in and turned on, the PC won't start. I've already tried resetting it with a jumper, but it still doesn't work. Initially, the PC got stuck in Windows recovery, and after forcing a shutdown, this issue occurred.
I've test everything, gpu, ssd, ram everything is normal.

PSU has high capacity capacitors that can keep small devices like LEDs powered for long time even when disconnected from main power input. You should be able to shorten time by depressing Start button for few seconds. Blinking light usually means standby mode.
Getting stuck in windows recovery is usually sign of corrupted filesystem that may occur because of sudden power loss. I strongly suspect faulty PSU.