RD54 Stopped Spinning

Robert Jarratt robert.jarratt at ntlworld.com
Fri Apr 3 12:06:22 CDT 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
> Sent: 03 April 2015 17:26
> To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
> Topic Posts
> Subject: Re: RD54 Stopped Spinning
> On 04/03/2015 08:17 AM, Johnny Billquist wrote:
> > On 2015-04-03 09:58, Robert Jarratt wrote:
> >> Bit of an update. I put the transistors back as they seem to be OK
> >> and applied power to see if probing around would show anything. The
> >> Z8 was getting power, and the transistors did heat up within a few
> >> seconds, but the disk did not spin at all.  Is this going to be a
> >> problem with the motor itself?
> >
> > Brushes of the motor (if they have them) would be one thing to check.
> > Check if the motor is getting power?
> >
> If six transistors, then it is brushless (I'm sure that is true). But, you should
> check the Hall sensors.
> Likely one may have failed.  There should be 3 sensors in the motor, at any
> time they should be in a state where one is high and two low, or two high and
> one low.  So, turn the spindle while checking the 3 sensor signals, all should
> cycle.
> If the sensors are OK, then the logic going from the sensors through to driving
> the power transistors is not working.
> make sure the crystal oscillator is running, that regulates the motor speed
> controller.

Yes, it is 6 transistors.

All this sounds like I am going to have to open up the disk to get inside as the motor is on the inside. I don't think there is a way to turn the spindle without opening it.

Interestingly at one point it started working again. Then after I put it all back together again, it stopped working once more. In one case, it seemed to start spinning when I changed the disk's orientation (on its side rather than flat), almost as if it just needed a mechanical encouragement to get it moving. But now, no matter how many times I try, and what different orientations I try, it doesn't work. Does any of that help with pointing the finger at all?



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