4 Apr
2015
4 Apr
'15
2:51 p.m.
-----Original Message-----
From: cctech [mailto:cctech-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 04 April 2015 22:18
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic Posts
Subject: Re: RD54 Stopped Spinning
On 04/04/2015 04:06 PM, Robert Jarratt wrote:
sensors to
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 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.
few
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 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.
Thanks. There is no critical data on the drive. I just wanted to use it to
show my MicroVAX II at DEC Legacy (in the UK next week) working without
booting off a network :-(
Regards
Rob