A weird issue appeared on my desktop computer. After a few reboots via reset button in a row (was fiddling with bootable USB stick etc), PC refused to boot. Thought it was the PSU, but no. Then after some random fiddling, discovered the following happens.
If I disconnect the main power cable from the PSU to the motherboard, then plug it back in while the PSU is powered ON, everything works normally. The small LED i have on the graphics card lits up (GPU is powered), the small network led on the motherboard lights up (powered), pressing the power on button starts the computer.
In that "working" state, if I shut down the PC properly from Windows 10, I can start it back on with the power up button on the tower.
If I disconnect the main power cable from the PSU to the motherboard, then plug it back in while the PSU is powered off, or power switch on PSU is on but the power cable is disconnected, then I plug it back in the socket, or switch the PSU on, then the leds on the motherboard and GPU are blinking extremely dimly, I can barely see them, and the power up button does nothing.
The first time the PC boots up in the "working" mode, I get a "American Megatrends" logo and message saying "Please enter setup to recover BIOS settings, Press F1 to Run Setup". I press F1, and simply "Restart" and the following times it doesn't happen anymore.
Checked PSU by shorting the green & black cables on the motherboard connector, this properly powers on the PSU fan.
Basically it seems the motherboard is working properly only when at the moment of its connection to the PSU, the PSU is already on, and remains on. If there is for example a electricity cut in the building or the flat for a moment, I need to unplug the power from the motherboard, turn on the PSU and replug the motherboard to be able to boot up the PC again.
Is it the PSU which is faulty ? Is it the motherboard ? Is it the CMOS battery (doubt it) ?
Never seen this before in my life.
Motherboard is Asus H87M-Plus, PSU is a Antec 500W one, CPU is Intel Core I7-4770, 16GB RAM, Nvidia GeForce GTX 960
Thanks a lot :)
51 Answer
What you can do, in order:
- Try to reset the BIOS (delete all BIOS passwords before doing that, if any)
- Try replacing the CMOS battery
- The NVRAM might be failing in the motherboard, so professional help might be required.
