RD53 Disk Not Rotating

It's been about 10 years since I looked at one, and then I didn't need to repair anything in that area. So I am not very familiar with it to put it mildly. There are normally 2 sections of such drives that use power transistors. One is the spindle motor driuer, the other is the power amplifier to drive the voice coil positioner. The latter is likely to be a full-H circuit, using 4 transistors (2 NPN and 2 PNP most of the time). Most spindle motors are 3 phase, so expect 3 identical transistors to drive the windings. There could eb anotehr transitor for speed control, or braking, or... I don;t know how hard it would eb to trace the connections from the positioner conenctor or the motor connecotr back to the transistors, but uou might discover which are which that way. Well, it might tell you whether the fault is in the electronics (repairable) or in the motor itself (much harder). My worry is that if there's a shorted power transisotr, or a fault that causes oen ot be turned hard on, it could damage the motor windings. Or if there's shorted motor winding, or a fault with the hall effect swtiches that cuases one transistor to be on all the time, then it might damage the tranasistors. But I think that;s unlikely, and it should eb OK to swap the boards. Just don't blame me if it isn't :-) I just hope it's not a problem in the motor. With a very few drives -- the Micropolis 1200 series 98" winchesters), it's possible to dismantle the mtoor without having to pull the HDA apart, but even then you need special tools. With most drives it's impossible to repair winding or hall effect switch trouble without taking the heads and platters out. Good luck! -tony