PSU +5V Standby Delay?

[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 PC will not start by pressing the PC ON button until 10 secs after switching on the PSU. I changed the CMOS battery and loaded the BIOS defaults but this made no difference.

I disconnected the main motherboard cable and found it takes 5 secs for the +5V standby voltage to appear on the PSU motherboard cable 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.

There is a power indicator light n the motherboard. This light stays off for 5.5 secs when the PSU is switched on then flashes for 0.5 sec, turns off, flashes again at 8 secs for 0.5 sec then stays on at 10 secs. The PC can then be started after this 10 sec delay. Windows starts OK and the PC is stable under heavy processing load.

I suspect the XFX +5V standby output is faulty. What is the specified time for an ATX PSU to establish the +5V standby output after power on and what faults could explain the behavior of my PSU? This is the second XFX supply to give me problems - the first one died completely after only a year.

 

[rar_54]

Turning off your power supply shortens the life of the capacitors since it exposes them to repeated charge / discharge cycles. An ATX power supply is in a "soft-off" condition when your computer is off and is providing a small 5V charge to the motherboard/ This is what enables the motherboard to turn the power supply ON when you hit the power button on your PC. Your "test" is only confirming a normal psu startup when you flip the power switch on the psu and it initializes to a 'soft-off' condition to supply minimal voltage to the pc. Repeatedly turning your power supply completely off and on is not necessary and is in fact considerably shortening the life of the supply.

 

[Scott_D_Bowen]

Maybe the capacitors in the PSU are slow to charge and don't hold their initial charge correctly.

I'd call it defective.

Get a Seasonic unit instead, they QA their PSUs much better.

 

[DSzymborski]

Maybe the capacitors in the PSU are slow to charge and don't hold their initial charge correctly.

I'd call it defective.

Get a Seasonic unit instead, they QA their PSUs much better.

It is a Seasonic.

 

[steve489]

Thanks for your replies. I prefer to turn the PC off at the mains since it saves energy and reduces the fire risk.

I'll return the XFX (Seasonic) PSU for repair/replacement. I'll buy a new PSU due the repair delay and keep the XFX PSU as a spare - I don't trust them anyway having had 2 fail in 3 years.

The EVGA SuperNova G2 850W PSU (made by Superflower?)is available in the UK at a reasonable price, gets excellent reviews and is listed as a Tier 1 PSU on Toms HW. Is this a good choice and better than XFX PSUs?

 

[steve489]

This XFX 850W Pro PSU has now failed totally. There is no +5V standby output when the PSU is turned on. I've now had two of these PSUs fail with the same fault. The first one lasted 1 year and this one 2 years. This seems to be a relatively common fault with this PSU and I now suspect there is a design flaw in this PSU. I'll get it repaired/replaced as a spare but I'm now using an EVGA Supernova P2 PSU instead. My PC is now running fine with the EVGA PSU.