Hardware Mini2440 Power Broken

Hello guys, 
My mini2440 power plug is broken,I want to solder it, but i don't know
which one is the positove pole, ground pole, could you please tell me, what
is no1, no2, and no3. here is the images

1 and 3 are -ve and 2 (the centre contact) is +ve.

1 and 3 are connected together.

I made a metal bracket ... basically a thin piece of sheet ally, about
1-1.6mm thick that has a hole drilled in it that fits around the round
front edge of the DC socket and the other end is clamped under the screw on
the RS232 connector.