Why does my PC hum?

[valkiln]

A while back I realized that when ever I turned off my computer, it makes this high pitch humming sound. Its not causing any critical problems but it makes it hard to sleep. I found that if I unplug the computer and wait a couple seconds before plugging it in again, this solves the problem although a few times it doesnt work on the first attempt. Does anyone know how to put a permanent end to this problem.

[Kurt]

Open it up and see if the fans are turning would be my suggestion. It might give you a more accurate source of the hum.

[noodles]

Mine does the same thing, except it only does it when it's on.

[valkiln]

Yea, I assumed that it was the power suppy fan but havent gotten around to check it out.

[Kurt]

Yea, I assumed that it was the power suppy fan but havent gotten around to check it out.If you're lucky, you've got a minor mechanical problem like crap in between the casing or hair wrapped around the blades or something. If you're unlucky, I have no idea. You might want to call Steve Jobs, even though he didn't make the computer, or even the company. I have his number here somewhere.

Hell, ask DarthBrady, he probably knows. I've only had a fan problem once and I fixed it with a toothpick and a butter knife, whereas he works with computers for a living.

[valkiln]

Thanks man I check it out as soon as I get home.

[DarthBrady]

A while back I realized that when ever I turned off my computer, it makes this high pitch humming sound. Its not causing any critical problems but it makes it hard to sleep. I found that if I unplug the computer and wait a couple seconds before plugging it in again, this solves the problem although a few times it doesnt work on the first attempt. Does anyone know how to put a permanent end to this problem.

I am here. Sorry I have been slow with answers, I have been very busy :)


Dont worry Valkiln, This is very common, most of my Newer PC's Do the same thing. I get at least 10 PC's a month with people asking the same question. 9 out of 10 times, there is no problem. This is very difficult to explain, I will do my best to make it easy.

There are many common reasons this occurs, especially in PC's Pentium 4 and higher. I first started in researching this when I bought a sony vaio in january this year. After upgrading to a new 750watt power supply, I got the "high pitch humming". Just as you described. I am still researching this, but here is what I have got so far:

Common Reasons this occurs:

1. Big power supply issues. - many power supply boxes ranging 300Watt and higher, have a "killswitch" breaker on the back of them. (look on the back of your PC, it should be near the power cord plug on the power supply. usually at the top of the tower).
When you turn off your PC, it's power supply's internal circuit transistors and capacitors still hold a lot of electric current. usually the main power circuit is designed with what is called a "normally closed" circuit, that will not open and stop electrical current from entering the circuit from the source-your power cord. So the constant current does not allow the power stored in the trransistors/capacitors to dissipate, or "empty" causing a high pitch electromagnetic frequency to be heard coming from your PC's power supply.
*this can be solved normally by simply reaching around the back of your PC and hitting the "killswitch" if you have one. If not, just unplug you PC.*

2. The motherboard power/protect light issues. - OK, have you ever been near a flourescent or LCD light in a quiet room, and heard a "humming" sound? that pretty much the same principle here.
Most every modern motherboard, has somewhere on a tiny LED light, that can indicate to a repair technician whether or not there is any electrical current going to the motherboard. (if you have a "normally closed" circuit as I described above, this light will remain lit up after you PC has been turned off and is still plugged in - the power supply killswitch should turn the light off after a few second of being switched off).
Anyway, this light gets very warm as your PC runs. And just light a large light, it emits a frequency of sound as a result. Because of the small size and milliamp rating in the tiny motherboard light, the sound is much higer pitched than a large light. Nothing to worry about. Just follow the same steps as above, hit the killswitch breaker or unplug your PC.

3. Too many plugs on one circuit. this is very common, and easy to correct. I know its easy to just get a 10 to 15 plug power strip to plug all you power cords into, but somtimes causes this noise. try not to plug everthing into the same wall outlet, spread them to another nearby outlet if possible.
Also, if your PC is plugged into an outlet in your house that uses the same circuit breaker/fuse as a refrigerator or freezer, can cause this problem and electromagnitic field interference, whic can also lead to this result.

Stopping problems like these for good can be extremely difficult, and is usually gonna cost you some big bucks to pinpoint the exact causes and replace or reconfigure the components which are at fault. This type of service calls for very advanced electical knowledge, even I have to hire an electrician to test for this.

I hope this helps you, if you have any questions just ask.;)