Changed the battery and power adpater, reset SMC, and still nothing.

Dear all,

I have a Macbook Pro 13" Early 2011. The old battery wasn't charging properly, so I checked the status and saw that it went into Service battery mode. But just before that I thought it could be the power adapter because it had some wear.

So I changed the battery (bought a new one here @ ifixit) and installed it.

the computer was working perfectly and I didn't realise that it still wasn't charging. Ok, reset the SMC. Nothing changed: new battery status normal but not charging and one thing that is constant throughout this whole process: the mA is negative (don't know what it means).

Now my computer has no power even to come on.

I'm going to use a friend's computer to recharge the battery, but I don't know what to look for any more and would like to have an idea of what could be the problem (hardware maybe) before I get to take it to repair.