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Whistle from motherboard when programming through LPT!

Discussion in 'Misc Electronics' started by Valentin Tihomirov, Nov 14, 2003.

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  1. Case of my PC is open and I hear weak whistles when programming EEPROMs
    using LPT. The application is mine, driver is not. What can produce the
  2. Andre

    Andre Guest

    The little filter caps on the LPT port might be slightly piezoelectric ? :)

  3. This can be caused by two simple phenomena. The first is power supply
    droop. I have had this happen on electronic devices before and it was cured by
    slightly larger filter capacitors. The second is that some devices undergo
    constriction effects in rapidly changing electrical or magnetic fields. The
    whine from a television or monitor is due to magnetostrictive effect in the
    transformer, and some ceramic capacitors are also known to do this, due to
    voltage induced dimension changes. In other words, something similar to
    piezoelectric effects.


    Chip Shults
    My robotics, space and CGI web page -
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