Please see the link to the guide below...
Bricked Midi fighter Guide
http://bit.ly/Ssp6pb
For older model midi fighters without the red reset buttons on the board a similar but different method is used found here.
http://www.djtechtools.com/forum/showthread.php?t=17824
http://www.djtechtools.com/forum/showthread.php?p=245493
These methods have fixed about 80-90% of broken Midi Fighter Classic's and Pro's