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 Post subject: Solution to coil whine
PostPosted: Mon Oct 06, 2008 8:26 am 
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Joined: Sat Oct 04, 2008 3:29 am
Posts: 96
Location: Edinburgh
I recently built a system with a GeForce 9600GT and was a bit disappointed to hear the strange noises coming from the PC. I've googled my head off trying to find out what's happening here, and that's how I found these forums...

Anyway I worked out the noise was actually coming from the PSU, not the graphics card, even though it only happens during graphical operations (including such trivial things as selecting menu options would make it click), and didn't happen at all before I installed the GLX drivers. The PSU, for information, is an Antec Earthwatts 380W

What seems to be happening here is that the PWM signal from the voltage regulators on the graphics card are getting back up to the power supply, and shaking that big old inductor all over the place. Not wanting to open up a brand new PSU, I thought, there must be a better way to solve this problem.

So... I put a 4700uF capacitor across the 12V rail, wired into a PCIe power extension lead. It doesn't completely eliminate the noise, but it certainly reduces it. I guess more capacitance is required. I should maybe make some sound recordings with and without it.

Oh and of course I take no responsibility for any damage you do to your computer by trying this out! I can't imagine what harm it could possibly do, but you never know.


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PostPosted: Tue Oct 14, 2008 11:38 pm 
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Joined: Mon Jun 09, 2008 3:46 am
Posts: 17
Location: Internutz
Neat idea. Have you seen photos of Intel's recent "Home theatre" targeted Mini-ITX boards? You'll see they potted the coils in some kind of ceramic or rubber. I was thinking about mixing some epoxy, making up a "cookie cutter" for my coils and encasing them in epoxy, but I like this electronic solution. The only possible risk that comes to mind is that of going over your PSU's max amperage rating and blowing a fuse. Since caps act as a direct short while they are charging, you could end up having boot problems if you go overboard on capacitance.


Also I read somewhere that TV servicemen occasionally paint coil windings with some kind of enamel which reduces whine.


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 Post subject:
PostPosted: Wed Oct 15, 2008 4:38 am 
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Joined: Sat Oct 04, 2008 3:29 am
Posts: 96
Location: Edinburgh
I have a "mark 2" in the concept stage, if I ever need another one. I thought maybe if I put a diode in there as well, it would stop the capacitor discharging through the other components when the graphics card wasn't drawing from it. That could improve things without the need for more capacitance.

I guess also something could be rigged up with a variable resistance in series with the capacitor, that is gradually reduced after turning on, to stop the initial power burst.


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 Post subject:
PostPosted: Sat Oct 18, 2008 9:07 am 
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Joined: Sun Aug 11, 2002 3:26 pm
Posts: 191
weboweb wrote:
Also I read somewhere that TV servicemen occasionally paint coil windings with some kind of enamel which reduces whine.

This was very common "back in the day" of serviceable televisions. The stuff was called "coil lacquer". I'd imagine that there are substances that would work better now available (materials technology marches on). Maybe just even a glue gun (?)


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