PC Doesn't Start on First ON Button Press?

[steve489]

I have an XFX 850W PSU and a Gigabyte GA-ZZX-UD5H motherboard.

My PC is normally powered fully off in Windows and turned off at the mains switch. To start the PC, I turn on the mains power (the PSU switch is already on) and then press the ON button on the PC front panel. The first time I press the ON button nothing happens, but if I press the ON button again after a few seconds the PC starts normally. All has been working fine until about 2 weeks ago.

Does this indicate a fault with the XFX PSU or motherboard and is there something I should check? When the XFX PSU is powered on by its switch at the rear, does it need to be left to stabilise for a certain time before my PC will start by pressing the ON button?

 

[profoundnoah]

You may want to check your header's connection to the MB. Typically its in the bottom right corner, just make sure that your power switch header (should be a small two socket pin labeled PWR) is plugged in firmly.

 

[steve489]

I've found the PC starts fine so long as I wait at least 10 seconds between powering on the XFX PSU and pressing the PC On button. This perhaps indicates the PSU needs a short period to stabilise before it will turn on - is that normal? Maybe I should try a PSU reset by turning it ON/OFF/ON quickly?

 

[profoundnoah]

Thats very odd, but thats what it sounds like to me. Just as long as your connectors are still snug, thats probably the issue. I admit I havent heard of that issue before as if you leave most PSU's on they're already stable.

 

[steve489]

Just to confirm - I only have this 'issue' when starting the PC from cold i.e. switch on at the mains plug (PSU rear switch is always on) then press the PC ON button. If the PC has been shut down but left plugged in and on at the mains, then it starts as soon as the PC ON button is pressed.

I also noted doing a cold start that it takes about 10s for my external USB HDD to spin up and the PC doesn't respond to the ON button until then.

 

[steve489]

I changed the CMOS battery since it was only 2.7V, cleared the CMOS and loaded the BIOS defaults. However, I still have the same start up delay. I noted the following behavior of the power button / light on the edge of the motherboard (next to the alphanumeric display).

1. Power on PSU at main switch after PC has been fully off for over an hour.
2. Motherboard light stays off for 5.5 secs then flashes for 0.5 sec, turns off, flashes again at 8 secs for 0.5 sec then stays on at 10 secs.
3. The PC will only start using the front panel power button when the light on the motherboard is fully on i.e. 10 secs after switching on the PSU.
4. PC then boots to Windows 8 OK and shows A0 on the motherboard display.

Please advise:

1. What does the flashing motherboard light on power on mean?
2. Is the 10 second delay before the motherboard responds to the front panel power switch normal or do I have a problem with the motherboard or PSU?

 

[steve489]

I've now disconnected the main motherboard cable and found it takes 5 secs for the +5V standby voltage to appear after the PSU is switched on. The voltage is stable at 5.14V once established. I suspect the PSU may be faulty since it should output the +5V standby sooner than 5 secs.

How long should it take generally for the PSU to establish the +5V Standby output?