Noisy modem/router (coil whine?)

Giroro · Jul 16, 2015

I recently bought a used Actiontec C1000A Century Link DSL modem/router and installed it. I find that it emanates an infuriating high-frequency noise/hum/mosquito buzz when powered on. I need to do something about it, as my apartment layout more or less forces me to keep it near my bed.

So I opened it up and applied hot glue to anything that looked like an inductor because I read that might help, and it didn't really.
I haven't been able to isolate which component this noise is coming from, which makes me think it is coming from beneath one of the heat sinks (the important one seems to be just a bent piece of steel soldered to the board, but many of the ICs are underneath some kind of thin metal shells).
I don't have pictures at the moment, but if that helps I can make it happen.

I am wondering if anyone has any bright ideas on what can be done about the sound? I'm thinking something along the lines of spraying everything down with a thick acrylic coating or something to see if that helps. Is there anything else worth modifying whilst I have it open?
I'm not super concerned about accidentally damaging anything as I kinda hate this thing a lot, and can't actually figure out how to return the rental modem (different model) that it's replacing.

cdabc123 · Jul 16, 2015

cover every part of it in inches of foam

photonboy · Jul 16, 2015

Foam will not do much IMO.

Is there any way to safely unmount the main board then use a piece of plastic or other insulated part to touch various components to see if that dampens the noise?

Not sure about spraying with acrylic. I'd have to do more research.

Other:
RENTAL return?

The website for the company you rent from will have the procedure for that. if you can't figure that out contact their SUPPORT. If still stuck start a new thread with the exact details (company you rent from).

If so you can locate the main source vibration.

Giroro · Jul 20, 2015

I'll be able to figure out the rental return, just saying I'm not out much if I break it

I went at it like you said trying to figure out where the noise was coming from when I was putting glue on the chokes and I couldn't even identify which side of the board the noise is coming from as both sides sound similar. Something about this frequency makes it very subtle and pervasive. I would half think it is a problem with my hearing if not for the fact it clearly stops when I unplug the modem.

Most of the ICs are covered in one way or another which makes it tricky. There are 2 long black components, not really ICs that are blocky and maybe 1cmx1cmx3.5cm (I'm not looking at it atm to measure). They are plastic and don't look familiar to me. I think whatever is inside controls the network switching? Given how long they are, if they were both sources of the noise, that might be why I can't quite pinpoint it. But I am unsure. Touching the casing on them didn't do anything, but if there are chokes or something hidden in there, then it probably wouldn't do much to just touch the case.

The wifi radio is off, so I'm pretty sure it's not that, at least. Feel free to speculate any ideas.

photonboy · Jul 22, 2015

Are you certain it's not the AC adapter?

Put your ear close to the main box AND to the AC adapter so you can see which is the problem. I have an adapter for a USB drive which makes a high-pitch noise.

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Noisy modem/router (coil whine?)

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