Re: anyone know where I can find a service manual for Disk II

[Silicon Sam <SiliconSam@gmail.com>]

On Apr 10, 12:16 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Silicon Sam wrote:
> > On Apr 9, 6:26 pm, Mike Willegal <m...@willegal.net> wrote:
>
> >>Hi Michael,
>
> >>        Are you sure about the analog recording thing?  I was speculating that
> >>whole track was simply written with some repeating pattern like 1s and
> >>0s.  Last night I was looking at the signals coming from a regular
> >>formatted disk  and it shows many of the same patterns that are seen in
> >>service manual, with a lot of added noise and jitter. I figure that the
> >>noise and jitter came from the sector headers and actual data not being
> >>a consistantly repeating pattern.
>
> >>Regards,
> >>Mike Willegal
>
> >>Michael J. Mahon wrote:
>
> >>>Mike Willegal wrote:
>
> >>>>Hi Tom,
>
> >>>>Perfect,  just need to find or make a good alignment diskette.
>
> >>>Finding may be easier--it's an analog recording!
>
> >>>-michael
>
> >>>NadaPong: Network game demo for Apple II computers!
> >>>Home page:  http://members.aol.com/MJMahon/
>
> >>>"The wastebasket is our most important design
> >>>tool--and it's seriously underused."
>
> >  The cats-eye signal was written on a floppy by a machine that had a
> > wobble between tracks 15 and 17 (or whatever two tracks) and that way
> > you had a perfect sine wave on your scope on track 16.  As I recall
> > Dysan charged $50 each for them floppies back in the late 70's early
> > 80's.  I wore out and messed up a few of them.
>
> That sounds different than the alignment patterns I saw--
> maybe there were multiple approaches...
>
> How fast was the "wobble"?
>
> -michael
>
> NadaPong: Network game demo for Apple II computers!
> Home page:  http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."

  Not sure, but since the sine wave was a slow one, I would say it
only had to wobble once per revolution.  The object was to write a
signal from 1 track to the other, and measure the track in between.
Obviously the disk can sit still and the head move back and forth
between tracks while writing.  But it would have to be a mechanism far
more precise than the cam that Shugart and Alps used.

  Yes, there are several signals on the disk, this is just how they
made the cats eye recording.