# Faint Buzzing from PSU while Computer is Off



## NoviceTechie (Feb 2, 2009)

Hi,

Last year in January (09) I built a pc with an 850w PSU (ThermalTake / Toughpower / 850-Watt). By around November it started making a crackling noise, so I got in touch with the RMA department and they replaced it in about 2 weeks. I installed the new one and its nearly October now and I have a few questions..

First off, I thought I heard buzzing sounds, but it was more than likely the fan of my GPU, the CPU fan or the case fans so I dismissed them. But I got more curious so I powered the the unit with the case open and I heard very faint buzzing coming from the power supply. I've read that the PSU is never really "off," unless the power cord is taken off, or unless the PSU is actually switched off.. Is that true?

Also is the very faint buzzing normal when the unit is turned off? I read it could be the capacitors and it could be normal, but since I'm not an electrical engineer, I thought it was worth asking..


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## daz1 (Nov 4, 2006)

second paragraph true

third paragraph is known as capacitor whine (whining) normal ? not really it will probably die sooner rather than later


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## NoviceTechie (Feb 2, 2009)

I hope you don't mind but I have a few follow-up questions.

(Just for safety's sake, though I do plan to build a new PC this coming Jan 2011, I want to replace the current PSU.)

The "capacitor whine," does it sound like high frequency vibrating or buzzing? I'm just a bit confused because this forum had introduced the idea of "Coil Whining," which I'm totally unfamiliar with..What is coil whine and how do you differentiate from capacitor whine?

The forum also made me a bit scared that the squealing or whining or buzzing may be from the motherboard itself, though I really only hear it towards the PSU. In fact if I unplug all the PSU connections, and just plug it into a power source, I still hear a buzzing - what would you call that specifically?


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## daz1 (Nov 4, 2006)

getting a bit techy now , not a electrical genius myself, yes coil whine copper coils/springs can be from a resonence from audio signals /vibration etc etc and can be corrected with a bit of paper/hot wax capacitor whine is more related to a bad or failing capacitor http://en.wikipedia.org/wiki/Capacitor_plague


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## NoviceTechie (Feb 2, 2009)

gotcha - sorry all this information overload is kinda confusing me..

this forum says the capactior whine is nothing to worry bout..

every other post from techsupportguy indicated the whine was a sign of incoming failure..

But its definitely a bad sign when the unit makes the buzzing noise while the computer is turned off right?


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## daz1 (Nov 4, 2006)

i would say yes, i would not accept a buzz,whizz,pop,whine or fart from any of my computers so am siding with you, send it back !!!


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## jiml8 (Jul 3, 2005)

The buzzing is probably coming from the transformer in the power supply. All transformers buzz.

Old-style power supplies used a large transformer that ran at line frequency. They handled substantial currents at low frequencies, and they buzzed at twice line frequency. Modern switching supplies still use transformers, but operate them at much higher frequencies - which allows them to be a lot smaller and still do the same job. They have lower flux densities so they buzz less and at much higher frequencies, but they still buzz.

The buzzing occurs because these things have wire wound in a spool around a metal core, and they are magnetic devices. The core is typically laminated because this reduces eddy currents and heating in the transformer They run on AC, which means the current direction is constantly reversing. When the current reverses, the magnetic field reverses, and all the torques in the transformer reverse. This cause minute shifts in wire positions and minute movement in the core laminations in the transformer and gives rise to the buzzing noise.

I haven't heard a switching supply buzzing for a very long time. But, then, my hearing isn't what it used to be either. Nonetheless, if it is the transformer buzzing, it isn't a problem. If it is a capacitor squealing (and that is a different sound), then failure is imminent.


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## daz1 (Nov 4, 2006)

thanks jiml8 i needed saving there


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## NoviceTechie (Feb 2, 2009)

Is there a way to differentiate between the transformer buzzing and a capacitor squealing?

I guess the downside of forums is I have to be descriptive and I can't always be accurate.

Best way I can put it - the sound I hear is when the unit is plugged in - it happens whether or not the device is on or off. Its literally a buzzing @ a high frequency. Its like that sound you hear when you drive by an electrical plant..


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## NoviceTechie (Feb 2, 2009)

Can't emphasize enough, the part that worries me is that I hear the buzzing when the computer is turned off. As of right now I have the PSU separate from the computer. When I flip the PSU switch on, the buzz is on & it only disappears if I flip the PSU switch off..


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## jiml8 (Jul 3, 2005)

I edited my post slightly before I realized that there had been responses to it already.

Your power supply is not off so long as it is plugged into the wall and the switch on the power supply is on. The switch on the front of the box does not turn the computer on and off, it merely tells the power supply to bring main power up or bring the mains back down. The power supply has to be alive to be able to act on that signal.


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## NoviceTechie (Feb 2, 2009)

jiml8 said:


> I edited my post slightly before I realized that there had been responses to it already.
> 
> Your power supply is not off so long as it is plugged into the wall and the switch on the power supply is on. The switch on the front of the box does not turn the computer on and off, it merely tells the power supply to bring main power up or bring the mains back down. The power supply has to be alive to be able to act on that signal.


Ah I think I understand. So basically so long as the Power Switch in ON on the power supply, electricity is flowing and being regulated - therefore the Sound I hear while the computer is OFF, but the power supply is ON, is completely normal?

So from your perspective, going off of the descriptions I gave beforehand - my current PSU doesn't need to be replaced?

Lastly, do you mind if I ask for a description between the Transformer Buzz and the Capacitor Squeal? I just want to know what look for on future occasions (particularly when I build a new computer).


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## jiml8 (Jul 3, 2005)

If it's a capacitor squeal, you'll know soon enough. The squeal means the electrolytic capacitor is leaking, and it won't leak for long before you have a hard failure. Normally, they only squeal for a few hours - a few days at the absolute most - then you have a failure. Sometimes, that squeal gets loud too.

Most probably you are hearing the transformer. Like I say, I haven't heard one in a switching supply for years and can no longer really describe the sound they make. But for many years I flew radio controlled model airplanes with 2-stroke motors on them. Those things are loud, and these days I am hard of hearing as a result of it.

You are describing it as a buzz. That sounds like transformer to me.


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## NoviceTechie (Feb 2, 2009)

I think I understand. My previous Power Supply may have had the squealing. My current PSU buzzes @ a high frequency.. My previous one actually produced a crackling noise, which definitely didn't seem right.. I had that one RMA'ed asap.

In your experience, is the squeal really loud/audible/distinctly noticeable? I believe the previous adjective to describe it was that its a _whining_ noise.


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## jiml8 (Jul 3, 2005)

I've heard big electrolytics start squealing at a hundred dB or so. Yeah, it can be rather noticeable. But that is not common, and such large electrolytics are not found in modern switching supplies - and neither are the voltages that these big cans would see. If you have one squealing, you'll notice it alright. The more noticeable it is, the shorter the time it'll do it.


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## NoviceTechie (Feb 2, 2009)

Ah gotta go. But thank you jiml8 & daz1 for all your help. From everything you guys have posted, I don't think I have to replace this PSU immediately & you folks saved me the RMA time / shipping costs q;

Have a good day


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## NoviceTechie (Feb 2, 2009)

Things are getting a bit stranger. The sound that appears when the PSU is "on," but the computer is "off" has disappeared. I'm not an electrical engineer, but would that have to do with the outlet I was on? I was thinking maybe since it has been unseasonally warm, the entire house must be using more electricity than usual and maybe its causing some distortion on the line? Does that make any sense?

Or my conservative guess was that turning off the unit for this time gave it enough time to reset/discharge itself?


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