Macbook Pro 2008 15 inch not starting up

[flyboy6060]

I have a 2008 15inch Macbook Pro. It will occasionally start up but about 95% of the time it won't turn on. Once turned on it will stay on (until I turn it off) but if I let it go into sleep it will not turn on again. If I power it off it won't turn back on again also (except for the 5% of the time that it does). I have tried all the normal items like the SMC reset. I have brought it to 5 apple genius bars (I travel a lot) and everyone says they have no clue. Yesterday I opened the whole thing up and took a look. I blew out everything with compressed air and I took the hard drive out and replaced it with an older one (I wanted to put the SSD one I had it there in my wife's computer) and when I got done putting all the things back together (keyboard, 30 screws etc) it started right up. Then, of course, it won't start up again. Any ideas as to what to replace? I have been told a new logic board by a couple of shops but I decided to just buy a new macbook pro (which I am typing on now with) but I would love to fix that one! Thank again in advance!

 

[honestone]

Given that you cleaned the inside, and changed the internal drive for an older (assume it is/was working fine?), an issue with the logic board seems the likely culprit.