Chosen Solution
Mackbook pro 15 late 2010, no power. Lamp sil flashing 3 times
Ok, you have a RAM issue. First thing to do is to reseat the RAM. Here’s how: MacBook Pro 15" Unibody Mid 2010 RAM Replacement That failing you need to test both the RAM and the slots. Use only one stick, Put it in the bottom slot and give it a try then move it to the top slot. If it works, you know the slots are good and the stick is good. Do the same thing with the next stick. Now you have a better idea of where you stand. If it is a slot let me know and we’ll work on fixing that.
