Laptop power issues can extend to a number of different possibilities. I don't know if you have an AC/DC Mains screwdriver, but I know the general use ones are for AC, and your laptop uses DC power, as well as those things can give false positives (had one trigger on my belt buckle). Personally I think that a multimeter is a better tester for your situation, and the first thing I would check is the AC adapter to make sure it has enough voltage to power your laptop.
You mentioned that you cleaned your laptop with Benzene, which is a pretty heavy duty chemical, and is something that I would not consider using to clean a computer, due to the health implications, but I cant say that it would damage the board, even though that stuff is highly flammable (Isopropyl Alcohol is my top choice). I do have to ask, what prompted you to clean the board? Liquid damage is really the only reason I would consider manually cleaning a board versus simply blowing away the dust.
If its still open, you can check your power port with a multimeter to see if the port is damaged, but make 100% sure you don't make contact with the board while it is plugged in and set the board on a soft antistatic surface (I like shipping foam). I have seen instances where the hot lead from the DC jack burned out from a fracture, and where it simply burned the contact with the board. If you have never soldered before, I highly recommend bringing it to a professional before attempting to put a new port on yourself.
Finally, if you are positive the DC jack and the AC Adapter are good, and you pulled everything off of the board and it still won't power on, then you most likely have a dead motherboard, which unfortunately I see a lot in my line of work. The only fix for it is to replace the board; I don't know anyone that diagnoses and fixes complicated boards like that nowadays.
Good luck, and hopefully it's something simple like the AC Adapter.