If my search for a 400k drive comes up short and/or if time allows later
this week I'll work on seeing if I can ID the motor controller IC.
There are two PCBs in the drive, the top of the platter goes through one,
Waht do you mean by 'platter'? Surely not the disk itseld?
and the bottom of the platter goes through another.
When I open it up
again, I'll take some pictures.
it's very possible that one of the PCBs, probably the upper one, is the
spindle motor circuitry. If you are very lucky, it will be similar to the
motors in other Sony drives of the period, and will have similar control
circuitry.
I think there are some photos of a 'standard' Sony drive (in bits) in by
Flikr account (tonyduell). Do the parts look anythting like that?
-tony