Macbook Pro power issue.

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I have a few macbook pro A1226 macbooks. They all have the same symptoms. When you plug in the power supply and try to power them on all you can hear is the hard drive spin, fans do not turn on. Now when I press firmly on the memory slot(from the trackpad side) the macbook will power on and fans spin and it works. Now all of these macbooks came in to me broken(defective video) and I had new gpu installed on them. You are probably thinking that not all of the solder balls are connected and when I press firmly they get connected, but I have tried few different chips and these boards all have same thing. If anyone had same problem and can share some light, that would be very grateful. Thanks.