My computer speakers suddenly erupted in a loud ugly uncontrolable hum. Fixable?

A couple of weeks ago I woke up to find my desktop computer external speakers spitting out a loud and horrible hum. Nothing was playing though the speakers at the time; in fact, the computer was not even turned on. WTF, I thought.

A few other observations that might aid in a diagnosis of this problem…

  1. I switched out another set of speakers. They work fine, so I know that the PC itself is not generating the hum.

  2. The manual volume control on the speaker box had no effect in reducing the hum, but if I turned the control all the way to OFF, the sound stopped.

  3. As is customary, the 2 speakers were connected to each other by a wire. When I disconnected that wire, the one still-connected speaker continued to hum.

  4. These speakers are self-powered; that is, there is a line wire that comes from them that must be plugged into the wall. If they are not plugged in, they do not hum (or funtion at all). FYI, this particular pair has one of those transformer blocks at the plug end.

Does anyone have any idea what is going on here, and if it can be fixed? I have a suspicion that this is not a unique problem.

Thanks all, in advance.

I’ve seen computer speakers do this when near something else wireless, like a cell phone or a clock radio - anything in your computer room that might be putting out an EMF field?

  1. If the contact between the speaker plug and the computer is loose, the power generated by the external plug will cause feedback between the non-powered computer and the powered plug. Check the connection, and all should be well.

  2. If you accidentally plug the speakers in the wrong input, you get that sound. Check the plug and see if you plugged into the Line input or the Microphone input.

  3. Gremlins.

Or. if ypu are tired of “computer speakers”, the “line out” feed on the computer works fine with the “aux in” on your stereo.
(at least every computer I’ve built does this) If you have a stereo fit for the purpose - such as playing Cd/MP3/WAV, whatever.

Including a wireless PDA, which are notorious for “will you please move your Blackberry away from the phone?” requests during business calls.

Sounds like (heh!) the power supply for the speakers has failed - you’ve done a nice job of troubleshooting to find that the speakers are the problem, rather than the PC, and even better, to identify it as an internal problem rather than something like a bad cable that would cause a hum that changes in volume as you turn the volume knob up and down.

I’d wager that a capacitor has gone bad and is no longer filtering out the 120 Hz ripple from the incoming electricity.

It’s a 79-cent part, but if you don’t know how to diagnose these things, and how to work on them, you’re probably better off just replacing the speakers unless they’re really expensive.