Most of the problems are obvious due to the nature of currents involved. The IGBT and diode modules crack open. Some of the diode modules have internal SCRs to turn the main power on and off. Problems usually happen in the power supply section that is often a switcher are often of a common variety. These include sorted bridge rectifier, supply cap or switching transistor. If it gets beyond that, the problems won't be very easy. Some of these boards aren't supported very well and get cracks. What make and model do you have?
