Chosen Solution
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.
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.
