and replaced the keyboard, then assuming that the replacement keyboard is good, it is highly likely that you damaged something, not necessarily the logic board, during the install.
That the original keyboard does not work either, is worrying.
That said, perhaps you did not connect everything quite like it should be, those ribbon cables can be tricky at times, so it is worth going back in and checking all the connections.
A replacement logic board for the that machine will set you back almost as much as a new laptop.
Let us know what you find
A Macbook Pro was bought into the pawn shop I work at and it was working fine until a few weeks ago. It was missing 3 keys on the keyboard so I deceided to replace the whole keyboard.
Now it will not boot up at all. I was more than careful when disassembling the device especially with the power flex when removing the actual keyboard. I am hoping it is not the logic board as it is an expensive fix.
It came to the point where I put the old one back in to see if it would boot up again but no luck. I checked if the magsafe mains lead was going on another macbook as the LED wasn't lighting when plugged in.
The battery indicator on the left of the laptop is showing one green light (3rd from bottom) but it has been like that since, plus I don't think the battery had much juice in it to begin with.
I have done a lot of troubleshooting including reseting the PRAM and SMC which is what Apple support also told me to do.
Is there any other solutions that I haven't tried that may work. So far it has only cost me the price of the keyboard but a lot of time has went into looking to fix it.
I appreciate any suggestions you have and hopefully we can get this working. I now wish I just ordered the keys I needed of the internet rather than replace the whole thing.