ST506 drive not spinning...

[Tony Duell]

> 
> 
> Anyone know if an ST506 interface drive should always start spinning as
> soon as power is applied? I've never known one that doesn't, but I'm not

Yes, it should. AFAIK there is no motor-on signal on the ST506 interface 
or anything like that.

It's possible the drive needs to pass some internal self-tests before 
starting the motor (e.g. that the microcontroller ROM checksums OK, 
there's no current through the write heads, etc). But it shoudln't depend 
on the intenrface signals.

In the case of a real ST506, I am certain there's no way the controller, 
or any part of the drive logic, can stop the spindle motor. The spindle 
motor controller is a separate PCB with connections to the motor itself 
(coils, hall switch) and a 2 pin power input. That plugs into the logic 
board and carries +12V and ground. There are no other signals to the 
motor control PCB.

-tony