How to save two Mitsubishi M2896 drive (spindle motor smoked!)

Thanks Tony for your suggestions. What I means is: It happen in two distinct times every time when I used the drive to read through a PC with the software IMD to create images of floppy disks 8 ". Not having the correct power connectors i power the drives in this way: + 5vdc and ground coming by a PC power supply and +24vdc and ground from a Chinese power supply. I must have certainly reversed this last one even for a few seconds exchange +24vdc with the ground. Now both spindle motor supplied also with only +24vdc start smoking in the vicinity of the chip LB1620 and cause of cooling you can not touch it as hot it is. If I try to measure the resistance between pins +24vdc and ground of each spindle motor drive i get 1327ohm on FD0 while i measure 19ohm on the spindle motor drive FD1. There are no visible damage nor to the components nor the PCB wires. In both pcbs anyway the chips LB1620 sunburnt from not being able to keep a finger on it. I searched on ebay and the only place that has LB1620 seems to be: http://www.ebay.it/itm/LB1620-INTEGRATED-CIRCUIT-IC-BOX-74-/390955452872?pt= LH_DefaultDomain_0&hash=item5b06c2c9c8 The input's pins of the pcb are : +24vdc, ground, and the rest could be a control. The point is that I have no experience on these components. Replace the chip could make it burn again for my inexperience.