Faulty Apple Lisa 2/10 Drive - Problem persists

[Tony Duell]

> 
> >I think in my case if I had a drive with a spindle motor problem I
> > would see it through. YMMV
> 
> Well, on thinking further I might just do that.  I'm a little worried about 
> the micro-surgery but what have I got to lose?

Well, you don;'t want to make thigns worse if there's a chance you'll get 
more skills later, on the other hand, I would certainly agree that 
'having a go' is rarely a bad idea. 

> 
> I do have two drives and if a hall-effect device has gone in both there 
> still should be enough good ones to go around for just one drive, right? 
> I'm guessing they can be removed.

Yes, you can remove them non-destructively. They have 4 pins soldered to 
the PCB.. There are 3 in each motor, so if you only have one bad one 
pwere drive,you have 4 good ones which is enough to get one motor going.

> 
> Is there any obvious way to tell wether an individual one is faulty once 
> they are exposed?

Is there any way you could borrow an oscilloscope? It doesn;'t need ot be 
anyting fancy. What I would suggest doing is looking at the signals from 
the hall effect devices at the pins o the TA7259 (IIRC) chip, I think 
it's pins 1,2,3,4,13,14. If oyu have a ;scope with differential inputs, 
you could look at the difference betwene 1 and 2, 3 and 4, 13 and 14. If 
not, or if you're not sure about it, just look at each signal in turn 
using AC coupling. 

My guess is that as this motor is going to rotatge around 600rpm (the 
speed of the normal fixed-speed ones), the pulses will be a fre ms apart. 
This will give yoy an idea of what timebase setting to use. 

Anyway, what you are looking for is a signal or pair of signals that 
looks different to all the others. When you ahve foudn that, trace it 
back to a hall device and change that one.

Obviously you do this before dismantling the motor.

-tony