RD54 Stopped Spinning

Robert Jarratt robert.jarratt at ntlworld.com
Sat Apr 4 16:06:04 CDT 2015

> -----Original Message-----
> From: cctech [mailto:cctech-bounces at classiccmp.org] On Behalf Of tony
> Sent: 04 April 2015 20:57
> To: General Discussion: On-Topic Posts
> Subject: RE: RD54 Stopped Spinning
> > here the schematics of the XT 1140 from a basic four manual
> >
> > http://www.ardiehl.de/basicfour/download/mai2000/Maxtor_XT-
> 1140_Schema
> > tics.pdf
> Thanks for that, it is something I have been looking for for some time.
> Page 9 of that .pdf seems to show the spindle motor controller. My guess
is the
> 3 signals H1, H2, H3 are the signals from the 3 hall sensors in the motor.
I think
> I would start by seeing what is there (look as though they should be TTL
> so easy to check) and also see what the Z8 is sending to the motor driver
> circuits.
> Y1 is the clock crystal, see page 12 of that pdf. I assume it is
oscillating, do you
> see the expected 6MHz on pin 9 of U41?
> I don't think it'll be possible (or at least not at all easy to replace
the hall
> sensors. My guess is that  the angular position of the platters is
critical and they
> won't centralise accurately enough either.
> So I would only dismantle the HDA as a (very) last resort.
> -tony
> =

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?

Changing one of these sensors is probably going to be beyond me :-(



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