motherboard problem

superfast · October 22, 2019

1.everytime i turn on my psu, motherboard makes small sound, it almost cant be heared

2.and after i shut down my pc then unplug psu cable,i press power button on my pc, the pc is still turned off but

my mouse and keyboard leds is turned on a few seconds

simple question from two problems above : is my motherboard is still good? will it destroy my cpu and gpu?

mariushm · October 22, 2019

1. everytime i turn on my psu, motherboard makes small sound, it almost cant be heared

It may not be the motherboard, it could be the power supply.

Modern power supplies are designed to be capable of delivering a lot of power to components. To help with this, there are some components called capacitors which charge up with electricity and help smooth out voltage.

If the capacitors are fully discharged - something normal when the power supply was turned off for some time - and you turn on the power supply, these capacitors are very "hungry" and they try to "suck" up and fill with energy super fast and this can make the electrical panel in your house think the power supply is faulty and the safety fuses in your electrical panel could trigger to protect your house wiring.

In order to avoid that, power supply manufacturers insert a circuit which acts like a break, slowing down the capacitor, making it charge within a couple of seconds or so instead of let's say a tenth of a second.

The downside is that just like with regular car breaks, that circuit produces heat and keeps slowing the charging of those capacitors, which is not good, it makes the power supply less efficient.

So the power supply manufacturers add another component inside the power supply called mechanical relay, which is basically a switch, like the button on a ball point pen - after a few seconds, the power supply engages this component which makes an audible click and this component disconnects the "break" from the circuit and makes your power supply more efficient.

So that's the noise you may hear. A second or so after you turn on the PC, you'll hear that click and that's perfectly fine, it's just the power supply disconnecting that breaking circuit because it's no longer needed.

So it's safe and it's normal.

2.and after i shut down my pc then unplug psu cable,i press power button on my pc, the pc is still turned off but

my mouse and keyboard leds is turned on a few seconds

This is again something perfectly fine and normal. The motherboard also has those capacitors which get filled with smaller amounts of energy and help smooth out the voltage going to USB ports and various components on the motherboard.

LEDs consume very little energy and they can function with very little voltage and mice also work with very little power and voltage. So, if the motherboard has capacitors big enough, after you turn off the computer and remove the psu cable, the capacitors will still hold a bit of energy which is consumed slowly by the leds and mouse.

Also to mention: all power supplies are basically two power supplies in

1 : there's the big power supply which gets turned on when you push the on button on your pc, and this produces the standard 3.3v , 5v and 12v the components want, and

2 : there's also a very tiny power supply inside the power supply which runs 24/7 even when your PC is turned off and this tiny psu produces 5v stand-by, up to around 10-15w.

So for as long as you have the 24 pin psu cable inserted into the motherboard, the motherboard will receive 5v stand-by, which powers the chipset on the motherboard, the bios, and potentially some other things on your motherboard, depending on what options are enabled in BIOS..

For example, in the past BIOSes used to have an option to start the PC automatically when a fax-modem plugged into a PCI slot received a call signal. The idea was that you could have the PC shut down or in stand-by/sleep and when phone starts ringing, the PC could start within 10-20s and then the fax modem software would accept the call and take the fax and save it.

So to make this possible, the BIOS would send a small amount of energy to the PCI slots where such fax-modem cards were plugged in.

Nowadays there are options to power the network card with a tiny bit of energy, just enough for the network card to detect when a special signal is received. This is useful for example for network administrators to send a signal to all computers in a building and have them turn on, download some windows updates or a patch for some software like Adobe Acrobat Reader, install those patches and then shut down... all this without having to visit each desk.

Some motherboards also allow you to leave some USB functional and powered from this 5v stand-by tiny power supply... useful for using such ports for charging phones, or to turn on the PC by pressing a key on the keyboard.

So basically, don't be surprised if the mouse stays on even when your PC is turned off but power supply is plugged in motherboard. That BIOS option to leave the USB connectors powered may be enabled.

nextg3n · October 22, 2019

33 minutes ago, superfast said:

1.everytime i turn on my psu, motherboard makes small sound, it almost cant be heared

2.and after i shut down my pc then unplug psu cable,i press power button on my pc, the pc is still turned off but

my mouse and keyboard leds is turned on a few seconds

simple question from two problems above : is my motherboard is still good? will it destroy my cpu and gpu?

the LED´s turn on because of the condensators(prolly spelled it wrong) they keep electricity on them so even when the psu is not connected and you turn the pc on one time the led-s will blink for a second or longer... and it will use the saved power and thats it no danger or nothing...

about the mobos sound does it sound like some high pitched whistleing? or what kind of sound are talking about?