Z97 Extreme4 not powering on after unplugged

Hello all !

I have very curious problem with my MOBa.

When I unplugg my PC from electrical outlet (i switch off strip surge) and came back after a day (i use PC during evenings, every day) I plug it back (switch on strip surge) but the system does not respond to power and I cannot start PC (no lights, no fans). 
Oddly enough, after a 2-3 min of doing nothing the system comes back to normal state and i can start PC by pressing power button.
I have to add that after I plug power on, I can hear weird sound (beep, beep) in my speakers with decreasing frequency - it last around 20 sec and then slowly fades to consant low noise, typical when i speakers are plugged in, but there is no input.

Please advise - i am afraid that soon my PC will no longer be able to start at all !

MOBa details:
Z97 Extreme4/A/ASRK
Serial No. is 48M0XD055904

OK, i have asked around and unfortunately i cannot get any other PSU than new one from the store.
However i have a multimeter i can check the voltages on PSU, but i dont know where should i measure it on ATX power plug (24 pin), anyone can guide me to do it ?
Will that be a valid check for PSU ?

Owca wrote: Hello all ! I have very curious problem with my MOBa. When I unplugg my PC from electrical outlet (i switch off strip surge) and came back after a day (i use PC during evenings, every day) I plug it back (switch on strip surge) but the system does not respond to power and I cannot start PC (no lights, no fans).  Oddly enough, after a 2-3 min of doing nothing the system comes back to normal state and i can start PC by pressing power button. I have to add that after I plug power on, I can hear weird sound (beep, beep) in my speakers with decreasing frequency - it last around 20 sec and then slowly fades to consant low noise, typical when i speakers are plugged in, but there is no input. Please advise - i am afraid that soon my PC will no longer be able to start at all ! MOBa details: Z97 Extreme4/A/ASRK Serial No. is 48M0XD055904

Owca wrote: Hey, can anyone help me out here ? Is there a way to check PSU with only electric measurement tool (multimeter) ?

To review your situation:

If you remove AC power from your (unknown, mystery) PSU (PC power supply) via a surge strip, when you apply power to the PSU again, it takes several minutes before you are able to start the PC with its own power switch, correct?

After the PC does start, it runs normally and does not seem to have any problems, correct?

Question: If you do NOT remove AC power from the PSU overnight, does the PC start fine immediately in the morning with no waiting? My guess is that it would start fine.

Given this, my guess is the +5VSB (+5 Volt Stand By) rail in your PSU is starting to fail. When AC power is applied after being off over night, it takes several minutes for it to reach a stable +5V DC. That seems like a bad capacitor in that circuit, but who knows?

When a PSU is connected to AC power, and the PSU power switch is on, the +5VSB rail in the PSU will be on/active, and supply that voltage to the board. As well as allowing the electrical switch on the PC case to activate the rest of the PSU power circuitry, and cause the PC to start, it also keeps a few other parts of the mother board active, like the networking chip.

The power switch on a PC case is not a mechanical switch like a light switch. It is just a momentary contact switch that serves as a signal to the mother board and PSU, to activate the main voltage rails in a PSU. That is why we can "turn off" our PC with the Windows Shutdown command, which causes the mother board to send the signal to the PSU to deactivate the main voltage rails.

Testing PC PSU voltages can reveal nothing, because they are usually done with no load on the PSU. It works fine supplying zero Amps into a volt meter, but put a load on it and it is out of spec or fails.

This is the 24 pin ATX connector pin output, plus the others:



Pin 9 is the +5VSB rail pin on a 24 or 20 pin ATX connector.

It might be easy to verify the +5VSB rail is failing in your PSU, given the symptoms. You must only check the pin 9, +5VSB pin. The other +5V pins are provided by the main +5V rail.

Do not connect AC power to the PSU. You should have the PSU disconnected from AC power for several hours or over night, to match your failure situation. Connect the +/red voltmeter cable to the +5VSB pin (pin 9) and the black/ground cable to any COM (Ground) pin. Set the voltmeter to an appropriate DC voltage range, and apply AC power.

You are interested in the voltage in the first minute or two immediately after AC power is applied. If you do not get close to 5.0V immediately, or within a few seconds, the +5VSB rail is not working correctly. But you are testing with no load on the rail, so if you get 5V immediately, that rail could still be bad. The voltage tolerance on that rail is +/- 10%. The maximum current supplied by the +5VSB rail is 3A, in even the most expensive PSUs. Some PSUs only provide 2.5A, and hopefully not less.

You could check the other PSU rails, but I doubt they are the problem. For this testing, connect the voltmeter to the voltage rail (12, 5, or 3.3V) you wish to test, with the ground to any COM pin. Apply AC power to the PSU, you will get nothing yet on the voltmeter.

Using something like a paper clip bent into a U shape, short the PS_ON# (pin 16 on a 24 pin connector) to a COM/ground pin. That will cause all the main PSU rails to become active.

Question: Why did you think the board was the problem, when the component that is first in line to be affected by your habit of removing AC power from the PC, is the PSU?

The spurious sound through your speakers is random and is useless in diagnosing the problem.

Recording the length of time before the PC can start in the morning is also useless in diagnosing the problem.

The general trend of the delay time seems to be getting longer, as the +5VSB power rail continues to deteriorate. Soon your PC will fail to start, or take 10+ minutes to warm up that rail.

Why you continue to turn off power to the PC at night, I simply cannot understand.

Hi, I have the exact same symptoms.