Recent noise in addition to buzzing when reducing brightness on Imac 27"?

Discussion in 'iMac' started by ejosepha, May 29, 2010.

  1. ejosepha macrumors 6502

    Jan 12, 2009
    My week 13 Imac 27" has always made the buzzing noise coming from the top left of the computer when brightness is reduced below 70%, but I really couldn't hear it much when sitting directly in front of the screen so I lived with it. Now, after having had the computer for almost 40 days, there is an additional noise that I first thought was a fan coming on, but I don't believe it is. It's not the original buzzing, but more like an increased fan noise, though the fans rpms remain at their original normal levels. I see that I can get rid of the noise by moving up the brightness to maximum, and then down to minimum a few times. This works, but then eventually the this new fan-like, or higher pitched noise kicks in again.
    Any ideas on what this could be. I realized that increasing the brightness for the buzzing was like turning a halogene lamp up so that the regulator stopped making a similar noise. But now this has been added to the problem.
    Again, it disappears after sliding the brightnes up and down a few times (the original buzzing always remains though at the lower brighntess).
    Any clues of what I am dealing with?
  2. Btom macrumors 6502a

    Nov 19, 2009
    Problem (probably unstable) led back lite power supply.
    Apple Care, Apple Care, Customer Relations, New Computer (in this order).

    Tom B.

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