board repair

Hi all,

I have inherited a camtronics 2A driver board, a very nice board.
Wish I can have more of them.

Now I have a small problem (and a nice opportunity to learn board
repair) which I hope some electronics enthusiast/camtronic owner on
the list can provide some helpful pointer.

I may have reversed the polarity to the motor power supply. Now when
I apply the 12-18VDC to the logic side, the LED's does not light up.

I want to know what components of the driver board are most likely to
take a rest when the motor power supply polarity is reversed?

Thanking you in advance

Keongsan