4 Apr
2015
4 Apr
'15
2:17 p.m.
On 04/04/2015 04:06 PM, Robert Jarratt wrote:
So when I fired it up again with the scope, the disk
started to spin. This was a stroke of luck as I was able
to probe what I believe were the outputs of the hall
sensors. All three oscillated, but one of them showed
significant sideways wobble on the scope, which suggests
to me that the signal is not absolutely regular. It does
seem to suggest that one of the sensors is not working
well. However, would this be enough to explain why it
stopped dead in its tracks when it was working before?
Yes, the logic is generally
that you decode 6 legal states
of the Hall sensors to decide which of the 3 motor terminals
to drive high and low. if the Hall sensors give a signal
that has all 3 high, or all 3 low, the decode logic will
fail, generally leaving all transistors off. If it gets in
that state again, a vigorous twist of the drive around the
spindle axis might shift the rotor to a position where it
will start up again.
Changing one of these sensors is probably going to be
beyond me :-( Thanks Rob
I'd get the data off it quickly and retire the drive.
You
may only have a few minutes run time before the sensors go
more flaky and the drive shuts off. But, now that you know
the secret, you ought to be able to recover data, if that is
the plan.
Anyway, it seems you have completely diagnosed the problem.
Jon