I have a computer power supply that I've removed from its box and utilised as a power unit in a custom built computer case.

The problem is that the PSU whines a lot when the graphics card is used (it used to before, but it was masked by its noisy fan). Here is an mp3 recording of the sound it makes:

https://www.dropbox.com/s/8ip4tscyqysih14/psu noise.mp3

That's windows performance index's graphics tests, hence the variety in the sound depending on the graphics card noise.

As you can hear, it's pretty distracting. If I remove the graphics card from the computer, the noise vanishes (and no, it's not coming from the graphics card). I don't know much about power supplies, is there anything I should be looking at specifically on the PSU to replace? Or maybe clean up the 12v rail with a filter between it and the graphics card?

 

Hello,

It could be that the heavy load of the graphics card is giving problems.
How old is the power-supply?
It could be that the output capacitors have dried out and cause a rimple on the voltages when there is a heavy load.

Bertus

 

The PSU is about 5 years old now I think, and it's had almost daily use, though fairly light loads most of the time. It's a Corsair vx450w.

Is there any way to test the capacitors? They don't appear to be bulging or anything.

 

Hello,

I have taken one of the pictures and made some notes in it.

Bertus

 

Thanks for that. I don't have an ESR meter, so what I might try is replacing those capacitors if I have some equivalents spare and seeing if anything improves.

One question though... do those capacitors just help to clean the 12v rail? Is there any chance it would be possible to clean the rail using an external filter between the graphics card's power input (PCI-E power connectors) and the PSU if that's the case? Might be easier to try that if so? But then again I don't know much about power filters etc.

Thanks for your help so far Bertus.

 

Hello,

When you are suspecting the 12 Volts to cause the trouble, look for the capacitor that is connected to the yellow wires.
In the hardwarebook there is a desciption of the connector:
http://www.hardwarebook.info/ATX_v2.2_Power_Supply

The capacitor needs to be a low ESR type.

Bertus

 

It could be coil whine, happens quite a lot on ATX power supplies. What graphics card are you running?

 

It could be coil whine, happens quite a lot on ATX power supplies. What graphics card are you running?

I used a mic and placed it near various components and it seems to be coming from the various coils and also (maybe) the main transformer.

The graphics card is an nVidia GTX 460, which requires quite a bit of power (165w).

What I'm going to try is using a separate PSU to power the card, and see if that stops the whining on the main PSU. If it does, then I might look into making a filter to go between the card and the main psu.

 

Ok, so I have some interesting results.

Using a separate PSU to power the graphics card through its PCI-E power connectors, the noise basically becomes a none issue on the main PSU. I can still hear it if I put my ear to it, but it's basically gone.

I think the graphics card is definitely the source of this noise. If I put my ear to the graphics card, I can hear the same fizzy sound, albeit pretty quiet. The secondary PSU that's used to power the card also shows the fizzy sound, but only when the graphics card is plugged in.

So, can anyone recommend a filter that I can build to filter the power drawn by the graphics card? Would an RC low pass filter do, or would something more advanced yield better results?

 

Again if you think it's the graphics card then it's possibly coil whine or the cooling fan(s), it happens, and a filter will not help.

 

Look up magnetostriction.
It usually means you have a heavy load on a transformer or coil. Newer PSUs are running at higher frequencies and the effect is not usually noticable.

If it was an older model when you bought it, the technology could be 8 to 10 years old.

It is not a problem, it is just physics.

 

Look up magnetostriction.
It usually means you have a heavy load on a transformer or coil. Newer PSUs are running at higher frequencies and the effect is not usually noticable.

If it was an older model when you bought it, the technology could be 8 to 10 years old.

It is not a problem, it is just physics.

That could be it. Perhaps the card's power draw varies as it's drawing the frames, as each frame seems to correspond with the whining (so the higher the frames per second, the more frantic the buzzing sounds). What's interesting is that a card with similar power draw (nVidia GTX 660) on the same system results in the whining going away, despite the power draw being very similar (though slightly less). This is why I'm wondering if some kind of filter would help - if the graphics card is causing the whining by extremely fast variation in power draw, I would have thought that making a filter to isolate that 'noise' from the PSU would help IF it's possible.

 

if the graphics card is causing the whining by extremely fast variation in power draw, I would have thought that making a filter to isolate that 'noise' from the PSU would help IF it's possible.

If intermittent power draw is the problem the filter would need to provide an additional power reservoir of some sort to smoothe things. Perhaps the 'non-whining' card draws power in bursts above the audible rate?

 

Graphics cards run hot and are notorious for drying out the electros on the graphics card itself.

The result is that the graphic card draws high current pulses from the PSU instead of smooth DC. That will cause symptoms like you describe.

 

coils and transformers whine or hum with load. its a fact of life. ac magnetic fields and loose lamanations usualy. high frequecy transformers whine, due to the high frequency.

 

Get a higher power PSU.

 

What about a capacitor reservoir to smooth things out? I have some spare caps that might do, so I can give it a go... but let me know if my thinking is off on this one.

Get a higher power PSU.

I don't think that'll help. The system only draws 200w max even when the graphics card is stressed out with FurMark (a synthetic 'burn in' tester that stresses the card beyond realistic levels). The PSU is rated to give 450w, so it's barely stressed.

 

You could try replacing the primary electro caps first

 

Ok, that's probably sensible. I'll focus on the one's Bertus mentioned first. I'll have to remove it from the casing, but from what I can see through the mess of wires at least one of the capacitors looks like it might have leaked (just a bit on the very top). I'll get some replacements on order and update the thread with an update.

 

Better to replace the lot.
Say if 1000uf one is leaked replace all the 1000uf ones. Just a precaution.
Cause the 1000uf ones will have come from the same batch when assembled u know.
so even if the rest 1000uf ones OK, it won't be after a while
That's what I do.