Before wasting money on that, how big and how old are the drives? Really small newer drives have what are called IPMs, Intelligent Power Modules, that have all of the power devices integrated into one block, then they are often wave soldered to surface mount PC boards and it's almost impossible to replace them, so nothing is repairable. If they are old enough to have discrete power devices, it may cost more to fix small drives than they are worth. The components may not be made any more and if they are available at all, supply houses that still have them know it and make you pay. Larger drives are sometimes worth it though.
