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  #1  
Old 08-25-2009, 12:00 AM
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Default Intermittent PSU Whine

Can someone help diagnose my PSU whine problem?

My PSU will whine intermittently. Useually more when it is under a load, like playing Half Life 2. It does it sometimes at idle also, but if I hit the computer a few times in the right spot I can get it to stop (I don't hit it that hard).

I opened the case and I can make the whine start or stop by either moving the wires right where they come out of the PSU or putting pressure on the PSU in a ceartain direction.

Just as a temporary fix I pulled the wires where they will stop the whine and tied them there. It pretty much stopped the whine, but it did come back a couple times when playing games, but it was quieter and was much easier to make go away.

It is a 350 watt Antec PSU, but I think it is about 13 years old . I don't have the money to replace it right now and I would like to fix it if possible.

Edit: Also do you think i'm drawing too much from the old 350 watt PSU? I'm currently running:

P4 2.6GHz Northwood 800 FSB with hyperthreading
1GB DDR400
2 HHD's 40GB 5400rpm and 300GB 7200rpm
NVIDIA Geforce FX 5500 256MB
video card has a fan and I have an expansion slot fan. Planning on adding 1 or 2 more 60mm fans.

I can swap in a 5 year old PSU that doesn't whine, but it's a dell brand it is and it's only 250 watt.

Last edited by Alltracturbo : 08-25-2009 at 01:28 AM.
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  #2  
Old 08-25-2009, 01:33 AM
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In general, whines from the power supply are from a fan trying to bind up. If so, you can get by for a while by lubing the sleeve bearing. To do it right you take the fan out, remove the label, pull the c-clip and slide the shaft and fan out of the bearing. You clean the gunk and put a drop or so of light machine oil on the bearing and reassemble. Not all fans come apart this way. Getting the fan out also brings into importance of having the power supply off for a while and putting something over the electrical parts of the supply so you can't contact parts that potentially could still be charged.

The better way is to replace the fan with one that uses ball bearings.
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  #3  
Old 08-25-2009, 01:38 AM
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The noise you probably hear is caused by a loose core on a transformer or choke inductor.... the power supply works by rectifying the raw AC mains power to a steady DC voltage, this is then 'chopped' or in other words switched on and off at about 22,000 times a second (22kHz) and fed to a transformer... where the voltages are stepped down in our case and then rectified back to DC.... hence the name switch-mode power supply.

The are good reasons for doing it this way instead of using a transformer, one is efficiency, the size of the components that will have to provide something like 20 Amps, the weight are other examples imagine the size of a transformer supplying multiple voltages one of which needs to be around 20 Amps. Also rectifying and smoothing a 22Khz pulse calls for smaller components than rectifying voltages derived from a 50~60 Hz supply.

The noise generated I would imagine is either a raspy sound or a rough sounding whistle, what is probably happening is the core of an inductor used in aid of smoothing HF pulses is vibrating at the switch-mode frequency and it's harmonics.

This kind of fault 'may' easily be cured by locating the offending component and dropping some good strong epoxy between the core and the winding.... I did say 'may' because the core itself may not be accessible.

WARNING:
There ARE lethal voltages inside power supplies that can either kill or give nasty shocks - it's the volts that jolt and the mils that kill.... mils is the current measured in milli-amperes, that is a fraction of 1 Amp.

Power supplies are relatively cheap to buy and indeed if the age of the machine is more than about three or four years old it would certainly be feasible replacing it.

Sounds like the good ol' days of mending telly's .... if in doubt give it a clout

davy
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Old 08-25-2009, 07:52 AM
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Thanks for all the great info. I was thinking it wasn't the fan b/c I can make the whine start or stop with a slight movement of the wires right where they come out of the PSU, but just incase I was thinking of screwing another fan onto the PSU as a backup.

If I feel like opening it I can completely replace the fan. I have pleanty of different size computer fans and also probably another 5 or 6 power supplies I can pull a fan out of. I just don't want to use them b/c they are only 200 or 250 watt and I don't think that is enough.


If the whine is coming from a vibrating inductor like you say, would it do any harm to continue using it? Will is cause the PSU to fail faster than if I stopped the whine?

And if I do decide to put some epoxy on the inductor, how much should I use? Does it have to contact most of the coil or just a small spot? I looked up pictures online and some only have a small spot of glue on them and others are rapped all the way around with tape or rubber.
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  #5  
Old 08-25-2009, 02:59 PM
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An old trick I use when fettling video recorders and such like that undeveloped squeaks that are awkward to locate I got beer tube from the local..... and used it as a stethoscope was laughing stock of the workshop - it soon when missing on occasions, you know the kinda thing.... borrowed without asking.

Yes It certainly could well be the fan, they are easy to strip down, remove the back disc any sealing cap and a plastic retaining ring and out she comes... a drop of fine engine oil and it should last a fair while providing the bearing are not worn.... far easier to replace the fan.

But do bare in mind The direction of rotation of the blades, meaning dy'a want the air sucking or blowing theres also the amount of air that it can shift as well, ideally if you get one the same size and about the same power consumption then you won't go far wrong....

....Oooops the fan I didn't mention because I had the immediate impression from your post that it sounded more like a screech originating from a faulty choke or transformer, if the fan is that bad I'm sure you will be able to see it as it spins and screeches, I would imagine also if a fan was that bad it just wouldn't spin.... but you don't know your luck in a raffle so to speak. Also, you may find two little arrows on the side of the casing one telling you the direction of airflow and the other direction of blade rotation - some has em some hasn't.

Regarding the power supply wattage, you need one that is equal to or greater to in wattage of the one you take out, it is the mobo and your config. that decides how much power is drawn not the power supply itself, the power supply has to be able to 'produce on demand' if it fails we are in trouble has voltages will start to fall as soon as the load increases.... imagine a small guy and a big guy shifting a load of bricks, the smaller guy could rightly be expected to sweat more (but you get big guys out of condition mind) . From this you can deduce it's better to have a reserve of power has things will run cooler under full load conditions making things last a little longer.

Heres a little dinky power supply calculator, have a shufty just for fun, you'll find more links n' tips in the Sticky section here, at the top of this board.

Get a plastic tool.... NOT metal tool and have a prod, by using the minimum of pressure as you go along you should it the sensitive spot or item.

davy
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  #6  
Old 08-25-2009, 06:44 PM
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I definetly sounds like a high pitch electric screech or whine and I don't think it is the fan.

I do have a stethoscope, but I don't think it would be good at picking up that type of sound. A beer tube like you said would be good. Or just a regular tube with a small funnel on the end.

My problem isn't getting a power supply equal or greater than the one I take out b/c I put this computer together from a bunch of parts I had laying around.

The motherboard and processor are the only 2 parts I kept in the computer, but it only had a 250 watt PSU. I added a more powerful video card, DVD RW drive, another hard drive which is 7200 rpm, and 2 extra fans.

The PSU calculator you linked to doesn't have my correct processor or video card, but if I pick the closest things it says 329 watts.

I used this calculator and it says 293 watts. http://extreme.outervision.com/PSUEngine

Last edited by Alltracturbo : 08-25-2009 at 06:48 PM.
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  #7  
Old 08-25-2009, 08:43 PM
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Think you've come up with a possible answer there..... the average PSU is around 300 - 400 Watt mark, had another thought how about a 'dry joint' (a soldered joint gone bad) on say a smoothing decoupling capacitor now that 'could' create havoc.... seen that happen in folks houses and their cats and dogs go ballistics.

Always discharge the large smoothing caps (capacitors for short) theres usually two in on the mains side, with a 1K ohm 1Watt resistor or a house hold light bulb, sewing machine lamp or a fridge lamp are good for this - the incandescent type of course.... not the low energy garbage that looks like a half lit candle and takes about 5 minutes to get to full brightness!

Yep, noticed that those PSU (Power Supply Unit) calcs. vary from brand to brand. You mentioned Dell have ya seen this..... ? It's in the Lounge section along with one or two other goodies.

davy
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