On Thu, Jun 12, 2014 at 2:08 PM, Keith Lofstrom <[email protected]> wrote: > On Thu, Jun 12, 2014 at 07:28:37AM -0700, Dick Steffens wrote: >> My new computer is generating what sounds like a sine wave of about 975 >> Hz. It is fairly quiet, but noticeable. It is not constant, but nearly >> so. It fades in and out, and sometimes is not there at all. If I'm not >> using the running machine for awhile it goes quiet. I'm guessing it's a >> fan, but wonder what other folks might have experienced like this. I can >> take the box back to ENU for analysis and warranty repair, but it's my >> production machine, so I'd need to transfer some stuff to a backup and >> live with that while it's out. >> >> Any thoughts? > > If "new computer" == desktop, open it up and listen for the > precise area the sound is coming from. CPU fan speed varies > with CPU load, so I would expect a fan to vary in pitch as > well. > > Constant pitch, I would guess either the main power supply, > or the switching power supply on the motherboard. Power > supplies operate at ultrasonic frequencies, you wouldn't > be able to hear that. However, they have feedback loops > that control the output voltage, and if the feedback loop > is wonky, it will cycle around the setpoint, perhaps at an > audio frequency. That would be highly dependent on the > specific motherboard design, and the specific failure of > the feedback loop (connections? component? bad design?). > > Identify the source - power supply or motherboard (or maybe > even the disk or cdrom drive) - then google for that model > number and "noisy". > > If the problem is the disk drive, use "dd" in single user > mode to copy it to another similar disk drive NOW. If not, > put in another disk drive with a scratch distro and let > ENU have that. Disk drives are cheap, your time is not. > > Clinic is Sunday. You can bring it in and we can take a > look. If I remember, I can bring an oscilloscope and we can > probe around (and risk shorting something out, what fun!). > > Keith
Is it possible it is a beat frequency of two synchronous oscillators? -Denis _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
