The motors are old and obsolete; not much market for parts. Until recently, you couldn't even get impellers; you still can't get wp kits or carb kits. A schematic wouldn't help much, unless you were considering manufacturing your own cd box.
Any electrical or electronic component will fail eventually if their contacts, grounds are in poor electrical condition which can heat up any component and fail. All contacts including powerhead grounds where components connects to must be in shinny clean state and cleaned from time to time. This is overlooked, if connected should do its homework right, wrong..
