VOGONS


First post, by Justin1091

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Hi,

I've a CUV4-X motherboard for that I didn't use for some weeks, I wanted to reinstall it so put it in it's case again yesterday, after powering it up I noticed it had 'coil whine'. When I remove the videocard the noise is gone, tried 2 videocards same results. I've used the board for years and this is the first time it has this annoying sound. I tried two PSU's but same results, I'm sure it's coming from the motherboard just not sure which location.

Here is a picture of the motherboard http://hw-museum.cz/mb/46/asus-cuv4x:
First picture, bottom right - I noticed that coil (or choke or inductor don't know how to call it) is VERY hot to the touch (like I can touch it for 2 seconds then my finger 'burns'), other ones are cool. This is after 10 seconds after powering the PC on and sitting in BIOS. Is this normal? I have no idea if it was always so hot to the touch, might have something to do with the high pitched sound? Anyway I never replaced any caps on the board, but they all look OK, the ones near that hot coil do feel kind of warm to the touch though, probably because that coil is heating them up.

Specs of the pc:

Intel Pentium 3 800eb
256 mb ram
3dfx Voodoo3 3500tv (also tried a Geforce FX 5200)
RTL8139d NIC
Creative Vibra ISA

Reply 1 of 9, by nforce4max

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Check the caps as once they go even if they look ok everything else on the circuit takes a bit of a hit, probably shorted caps that are dry as bones.

On a far away planet reading your posts in the year 10,191.

Reply 2 of 9, by .legaCy

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nforce4max wrote:

Check the caps as once they go even if they look ok everything else on the circuit takes a bit of a hit, probably shorted caps that are dry as bones.

In my experience even new poor quality caps can whine, on a power supply that i replaced all the elecrolytic caps some caps i had to purchase locally and the store didn't have good ones, so i bought and tried and the regret was instant, not to mention that the psu couldn't handle any medium to high load.

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Reply 3 of 9, by Merovign

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If the coil is rocket hot that probably means it's vibrating, thus the whine. Now, this may be caused by something else, like the bad caps everyone goes to first because they're the problem 90% of the time, but I'd still want to replace the coil.

I have a Geforce card with *insane* coil whine, like deafening, and eventually I need to get replacement coils (the card's not in use now). Sometimes the adhesive that holds the coil dries, or gets pushed back or whatever, and then the coil can move freely.

There is probably a more elegant solution, like a different inductor design, that I'm looking for.

*Too* *many* *things*!

Reply 4 of 9, by Justin1091

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Thanks guys, it may indeed be the caps. Strange though that a month ago everything was fine (no idea if the coil was hot though).

If I were to replace the coil also, what is the correct name for it? How to find out it's ratings or whatever? I know how to replace capacitors, never done a coil before.
Anyway, because out of the 3 coils on the motherboard only this one is SO hot there is probably something wrong with either the capacitors or the coil right? Not normal for it to become so hot?

Reply 5 of 9, by .legaCy

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Justin1091 wrote:

Thanks guys, it may indeed be the caps. Strange though that a month ago everything was fine (no idea if the coil was hot though).

If I were to replace the coil also, what is the correct name for it? How to find out it's ratings or whatever? I know how to replace capacitors, never done a coil before.
Anyway, because out of the 3 coils on the motherboard only this one is SO hot there is probably something wrong with either the capacitors or the coil right? Not normal for it to become so hot?

Limited knowledge warning
As far as i know there is the inductance (which is measured in henry), there is a voltage rating, a current rating.
I would wait some more experienced user to comment about just to be sure.

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Reply 6 of 9, by pentiumspeed

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Diagnosing noises in computer is best done with a chopstick. Tap lightly on each components. Does not have to be a coil, it will look like donut, spool type or grey block, also tap on the each capacitor. If you tap or press on each when you get right one, you will know instantly. Drinking straw to ear aimed at item in turn works great.

Also, if you find the noisy coil, best solution is dilated varnish coating and let it cure. Hot glue is not right one.

Cheers, pentiumspeed

Great Northern aka Canada.

Reply 7 of 9, by Tiido

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If just single coil is hot compared to others the VRM has a failure in it, probably in form of a dead transistor though some ceramic cap could also short out.

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Reply 8 of 9, by Justin1091

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Allright guys, been asking the same question over at badcaps forums. Someone there suggested trying a pci videocard instead of agp to test.

Result:
Coil a lot less warm like -50% and no noise. Strange..

About finding the coil, good idea pentiumspeed. I'm now sure it's the hot coil making the noise.

@Tiido big electrolyte caps are probably fine then?

*probably* unsafe to have the PC on when the coil gets that hot right?

Reply 9 of 9, by Justin1091

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In case someone was wondering, it's fixed. Cause was a loose (it was shifted, didn't spot it earlier) ceramic capacitor near the coil. Removed it and soldered it back in: all good!