Printrboard heatbed output, won't turn off now (no replies)

Hey guys, search found nothing on this, basically my printrboard rev D was melting the heatbed plug
even at 60c so I hooked up a relay, it was working at first, but the plug was loose so I took it off,
tightened the connectors and accidentally put it on backwards :\ Needless to say I blew the relay,
the rectifier diode, and now that I replaced them I think I damaged the board, though everything else
works. What it's doing now is activating the relay immediately upon powering up the board, I can't
turn off the heatbed without powering down the whole board. I've been running without it printing PLA
but now I need to make some ABS stuff so I wondered if anyone knows what part of the board I should
look at replacing, the mosfet was my first guess but I'm not really knowledgeable about electronics
as of yet.

Thanks in advance for any advice :P