Coil whine issues

  • Any suggestions on how to reduce coil whine? Glues and epoxy suggestions are welcome, but I want to try to reduce it on the software side too so that I can make the hardware solutions even more effective.
    My pfsense system is a socket 754 laptop with a Turion ML-40 (k8 at 2.2 ghz,) an ati RS480M chipset, a socket 939 CPU heatspreader attached to the CPU with thermal paste on the CPU and super glue at the edges once it settled, a scythe ninja fanless CPU heatsink held on with zip ties, 512 mb ddr, a 4gb usb flash drive, an atheros mini pci wireless interface as OPT1 (labeled ath0) interface bridged to LAN, a relteak onboard interface as WAN interface (labeled rl0,) a USB NIC as LAN interface (labeled ue0,) and no fans connected.
    I am having coil whine issues. The issue wasn't present in ubuntu x86.
    I have had the same coil whine on pfsense 2.0.1 and 2.1 (i386 nanobsd_vga)
    I'm not sure if it is just normal coil whine, or something else.

  • Can't you hide it in the attic? (or reduce the no. of USB devices attached)

  • Wouldn't be a very good idea. In the summertime the attic gets past 60 C and the router runs by my estimate 20C above ambient at idle. Removing the laptop battery resolved the issue.

  • It might help to enable/disable powerd.

  • Netgate Administrator

    Having a built in UPS is half the advantage of using an old laptop. Seems a shame to have removed it. Was the battery dead? Drawing more current than it should perhaps.
    I used to work for a company that made transformers and coils of various types. Occasionally noise was an issue and the solution was almost always to use a polyurethane potting compound. That stuff does not conduct audio frequency vibrations, like almost completely. However it also doesn't conduct heat, like almost completely!  ::) You had to take this into account at the design stage, just potting an existing inductor could easily lead to overheating and insulation failure.


  • The battery is by my guess at least 7 years old. I tested the battery and it was dead, so I pulled it.
    I have a large UPS under my desk, so it isn't much of an issue.

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