Subject: 3400c Sleep light
Date: Sat, 12 Nov 2005 17:59:12 -0500
'Mornin everyone...
I have a question - I just noticed when I put my PB3400c to sleep, the
light blinks and all, but there's a little noise every time the light
comes on (It's like a slight click---click---click)
Is this a problem I should worry about?
Don't worry about it. Here's my guess: The sound is not the HD, it's
definitely not the LED (!), it's probably not coming from the speakers
(although it may be a bit difficult to verify that), but sounds more
like it's coming from a place near the trackpad. If so, then it's the
power supply internal to the PB switching modes. The noise comes from
the magnetics (transformers and inductors) -- they emit some sound,
either through motion of the windings, or sometimes from
"magnetostriction," although the noise is usually not very noticeable.
TVs, by the way, emit a high pitched whine from the flyback transformer
by the same mechanism. Some are loud enough to be very annoying.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Center for Integrated Systems, CIS-205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu
650-725-3709 voice, -3383 fax
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