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Mid 2010 Model A1278 / 2.4 or 2.66 GHz Core 2 Duo processor

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High frequency sound when brightness low or mid...

Hello guys,

I'm having a problem with my old MacBook Pro. It works great, but it's producing some high frequency sound on the left upper corner of the keyboard. I've mentioned that it's present only when the screen brightness is around the middle or a bit lower than that. When I move brightness to 0% it dissapears, at 1% I can hear that a little bit, 2% bit more and so on. I've also mentioned that the sound frequency is going up with every percent of brightness, but when it passes the middle it goes to high, so I can't hear that-(more than 20kHz?) It sounds almost the same when it's running on battery power...

What can I do about it? I have a schematics and boardview for my motherboard so I thought it can be some capacitor? What component can create a noise like this? I have one donor-board, so I can easily replace any component without a problem...

I can record a noise by your request, but I think that my explanation is clear.

Thanks.

Answered! View the answer I have this problem too

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It might be that the problem is with the Lcd panel. You can try setting your brightness to the level where the noise is at its peak, then turn off the machine, carefully disconnect the Lcd cable, keep it isolated from the rest of the board, restart the Mac and see if the noise it's still there.

Sometimes it's a bit difficult to spot exactly where such high frequency noises are generated.

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I've done that and there is no noise like before. There is a little of noise (I guess it's normal), but not that much.

Sorry, but I can't see why this method of removing LCD cable should give me some usable results. I'm sure that the noise is comming because of the brightness. When LCD cable is disconnected from MB, there is no power drain from the board, no action there, so it doesn't have a reason to produce any sound. Correct me if I'm wrong!

Some more suggestions?

Thank you for your answer!!

p.s.

The noise that I described in my first post sounds like CCFL inverter transformer in normal operation. Those are located as separated pcb in laptops which are using Cold Cathode Fluorescent Lamp for backlight.

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I have no idea of your technical skills and available equipment to troubleshoot further. By removing the Lcd cable, what one achieves is to try to get confirmations , help isolate the problem and rule out other possible faults. The easy way at this stage would be to have the Lcd replaced, that would give a more certain answer about where the fault is likely to be located. The other option is to troubleshoot the logic board by checking that all values are correct from the backlight IC to the LVDS.

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NeleRS will be eternally grateful.
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