High Pitch Noise from PSU - From Electrical Components?

SockMan!

2[H]4U
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Jul 31, 2004
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I'm hoping that you guys can help me since I'm stumped.

My power supply gives off a very high pitch noise; so much so that I'm the only one in my family that can hear it. This noise irritates me more than a delta screamer or tornado fan would. Understandably, I would like to silence the noise; hopefully without having to replace the PSU (It's an Antec SL350).

Apparently, this noise is not coming from the fans, but rather the electrical components. I've tried to touch most of the electical components (mainly chokers) with a plastic toothpick to try to pinpoint the source of the noise. I didn't notice any change in pitch though, so I tried some of the other components to no avail. I also tried stopping the fans, but that just confirmed that the noise wasn't coming from them.

Funny thing is: the noise is intermittent. For example, sometimes it stops temporarily after I move the mouse at the login screen. Also, the PSU has never given me any noise problems when it was in my other computer. Noisy line noise perhaps?

Does anyone have any ideas on what the problem could be? Or perhaps a solution to my problem?
 

Ronbo

[H]ard|Gawd
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hmmm, sounds like you have exceptional high frequency hearing and can hear the windings of the main transformer "humming" or vibrating at the switching frequency of the power supply. I'm told a lot of models use 19Khz as the frequency, so that is entirely possible that when the windings draw enough current, you can hear them. My hearing is shot from years of driving military trucks (even with ear protection), overflying jets, jets 200 yards from my barracks, and heavy metal music to hear much in that range anymore, but when I was younger I know for a fact I could hear 19khz, we tested in a science class. a possible solution is to apply some hot melt glue on the windings, this may help. A long term solution may be to listen to other people's power supplies to find one that switches in a higher frequency, like 25Khz which is above your threshold of hearing. LMK if this helps, or even if it doesn't
 

SockMan!

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Thanks, I'll try the hot glue idea. However, would the glue melt from the heat generated by the PS?

Also, is off-the-shelf hot glue conductive enough to cause problems?
 

Ronbo

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it's what the factories use so I doubt it, but if it fixes your problem for a while and melts, use silicone or epoxy to replace it. I doubt the temp of the tranformer exceeds 450 f which i think is the melt temperature, I'm not sure of that though. And AFAIK this stuff should be totally non-conductive, but it may be capacitive, but I doubt it will affect anything, the windings are insulated with varnish, and the core should not be attached to any voltage, esp if it's a toriodial transformer.
 

Ice Czar

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as Ronbo points out the windings would be a leading suspect

and here is an basically the same from gee, another EE we have that designs PSUs ;)


gee said:
What does it sound like? A fan will "whirr"... power supplies will give off a high pitched squeal, with some louder than others.

They dunk the transformers/inductors used in power supplies into varnish during manufacture, to hold the windings in place. Every once in a while a part won't go the full way into the potitng tank or sometimes a manufacturer will forget entirely... the loose windings and loose transformer core will "dance around" a bit and cause noise.

This doesn't cause any reliability problems, but it can be annoying as fuck.

Does the sound change depending on what you're doing on your computer? if so, this is your problem.

youll see hotglue throughout most supplies
often youll have a pulloff strand hitting a fan as well causing noise
I mention this in case anyone ever uses the search feature :p

and to that end
squeak squeal hum buzz humm pitched
 

SockMan!

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Thanks Ice Czar and Rambo! At least now I know what the issue is.

Unfortunately, it seems as though my liberal (and messy) use of hot glue didn't help at all. I guess I'll just have to shop for a new PS and demote this Antec as a backup.
 

Ronbo

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I generally don't associate the sounds people hear out of their PSU's with this, but it didn't sound like sizzling bacon or some other kind of frying or hissing sound did it? That sound in SMPS's is associated with what's known as "Chaos" and that's a bad thing to have in a (supposedly) highly regulated circuit. It's also a sign of impending doom as something is most likely operating outside of design specs,IE a "chopper" handling too much current.
 

SockMan!

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No, it's just a high pitch tone. No sizzling, grinding, popping, or any other malicious sounding doomsayers.
 

Ronbo

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OK, then odds are it's a winding loose in a place where the hot melt glue can't get :( anti-vibration mounting won't help it either, cause it's not a mechanical vibration.
 

SockMan!

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Well, thanks for your help anyway. At least now I have an excuse for upgrading my PSU!
 

Hypo

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I know what you're talking about, SockMan. I'm the only one in my family that can hear those noises too. It's funny, cause I can also tell when some older TVs are on just by listening.

I have a cheapo Linkworld PSU that I got for $20, and it does the exact same thing. When I replaced my sunon fans (they sound like a whirlwind) with some queiter ones, the noise was very obvious. So obvious, in fact, that I just put my sunons back and overclocked my system.

In my rig, it does this only after I've used the computer for a while. On bootup, it doesn't do the "weeeeeeeee" sound. And when it's REALLY noticeable is when I shut my system down and the PSU/mobo are still on. When I do that, I have to shut it down from the power strip.

But either way, if it bothers you that much, just get a new PSU. I would have returned mine, but for $20 I said it was worth it, because my sister now uses that computer. :D
 

Toronaga

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Dec 11, 2004
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31
It could also be the hard drive. That's what just happened to me. I spent 2 weeks thinking it was the PSU, but it turned out to be the hard drive.
 
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