MacBook only boots fully occasionally, otherwise black screen
Hi! I've got a MacBook which boots and works fine about 1 in 30 times I try to power it on, and the other 29 it makes bootup noises (but no chime), the optical drive revs up, the power light stays on, but nothing else happens. When it works occasionally, it works 100%, and stays on pretty much till I power off. The original owner was told by Apple that it's a GPU problem. I've tried different memory, replacing the DC-in, PMU and PRAM resets, and nothing seems to make a difference or improve the 1/30 ratio. I don't suspect the screen, because, again, when it works, it works. I'm just curious if anyone has any thoughts before I give up and assume it's a bad board.
If you want to see the machine, below is the video I'm using to sell it on EBay. I've been selling lots of MacBooks for parts lately, and would much prefer to sell this as a working machine! :-)