George (GGG) is a wealth of information on the slave boards, he has fixed a lot of them. A very common failure is the drive FETs, actually only one of them seems to fail most often. There is also a 27 ohm resistor associated that George says he sees failed at times. Finally, I think those SMT IC's on the top are on the list if the FET's and resistors are good. Again, GGG is the ace on these, he's fixed way more of them than I have.