6 Feb
2011
6 Feb
'11
8:27 a.m.
Thanks for that explanation Tony.
The switch is part mechanical and part light sensor. A plastic pin is
pushed down when the disk is first inserted (incidently, this pin is at
exactly the same location as the hole in a 3.5 inch HD disk which is why the
Lisa doesn't acknowledge those kinds of drives). This pin is joined at
right angles to a plastic block which cuts off a light beam thereby
activating the switch.
The plastic block is probsly what's called a 'slotted optoswitch' in most
catalogues. Inside is an LED (sometimes vixible red, sometimes IR) and a
phototransistor. Puting something opaque in the slot cuts the light off
from the phototransistor.
[...]
I tried manually moving the platter to different
starting positions before
activating the switch but whether the motor fired or not seemed random. It
is interesting that 2 or my 3 Lisa floppy drives have this symptom.
It may be a stnadard problem... Perhaps the motor control IC was a bit
underrated so it fails easil, or perhaps said IC was not particularly
reliable anyway.
Some fault on the circuit board for sure. My plan at this stage is to seek
Is there just one PCB in the drive, or is the spindle motor as separate
board? Can you identify the spindle motor controller IC? If not, what ICs
are on the board (and we'll see if we recognise anyof them)?
-tony