PC Will Not Turn On

[scussons]

The main PC components related to this problem are:
Gigabyte GA-Z77X-UD5H motherboard
Intel i5 3570K CPU
XFX PRO 850W PSU

The PC has been working fine for 11 months until yesterday. I switched on the PC at the mains but the PC would not start on pressing the PC power on button. No fans were running and there were no signs of life. The power LED on the Gigabyte motherboard was not lit. I then reset the XFX PSU by toggling the PSU switch on/off quickly. After about 1 minute, the power LED lit on the motherboard and the PC booted OK. After turning the PC off and switching off at the mains, the same thing happened again. I had to reset the PSU to power up the PC. I then noticed I couldn't enter the BIOS screen and flashed the backup BIOS to the main BIOS. So far things are back to normal!

Can someone explain what has been going on here? I assume the BIOS has been corrupted which prevented the motherboard sending the correct signal to the PSU to power up and somehow putting the PSU in a fault condition requiring a PSU reset??

How does the XFX PSU fault detection logic operate and what conditions would put the XFX supply into a fault state requiring a PSU reset?

 

[ganon11000]

sounds like the XFX PSU is failing. You'll need to RMA it with the 5 year warranty.
It is very rare for a SeaSonic (who make the XFX PSUs) to fail, hopefully this won't happen again with the replacement.

To be sure it is the PSU, test the motherboard with another PSU or use the PSU on another motherboard (although if the PSU is very faulty this could cause damage, hence I recommend using a "known working" PSU to test the motherboard.).

 

[scussons]

The PC failed to start again today but has been OK after another power supply reset. I noticed on switching on the PC at the mains but before switching on the PC that there is power to the USB ports. Is this normal since my old Windows XP PC doesn’t do this? Is may be time to return the XFX PSU or Gigabyte mother board under warranty but which?

 

[ganon11000]

The PC failed to start again today but has been OK after another power supply reset. I noticed on switching on the PC at the mains but before switching on the PC that there is power to the USB ports. Is this normal since my old Windows XP PC doesn’t do this? Is may be time to return the XFX PSU or Gigabyte mother board under warranty but which?

that is normal for some motherboards

 

[scussons]

I found I can turn the USB ports off by enabling ErP in the BIOS but then the PC won't wake from sleep even when pressing the power button to wake it up. Very strange!

 

[ganon11000]

have you got the latest drivers and BIOS installed?

 

[scussons]

I disconnected the XFX PSU from the motherboard and peripherals and tested for the +5V standby signal on pin 9 (purple wire). There is no signal even after trying to reset the PSU many times. The PSU is therefore now dead after only 11 months light use. I've requested a replacement from my retailer. Thanks to everyone who helped.

 

[ganon11000]

I found I can turn the USB ports off by enabling ErP in the BIOS but then the PC won't wake from sleep even when pressing the power button to wake it up. Very strange!

I disconnected the XFX PSU from the motherboard and peripherals and tested for the +5V standby signal on pin 9 (purple wire). There is no signal even after trying to reset the PSU many times. The PSU is therefore now dead after only 11 months light use. I've requested a replacement from my retailer. Thanks to everyone who helped.

It's rare for an SeaSonic (XFX) to fail. At least it went out quietly without a bang and/or killing all your components.