Re: A2 Joystick Maintenance

["Polymorph" <polymorph69@hotmail.com>]

Michael J. Mahon wrote:
> Polymorph wrote:
> > Polymorph wrote:
> >
> >>So thanks for your advices - I'll give the terminals a little solder
> >>after doing another round of cleaning (with contact cleaner) to
> >>*hopefully* remove any further WD-40 residue. I'll report my
> >>success/failures tonight when I get home.   ;-)
> >
> >
> > Well, after doing *heaps* more cleaning with contact cleaner and a
> > slight bit of manipulation of the pot internals (the sweeper?), I have
> > managed to get the old joystick functioning pretty well (and no
> > soldering was required). The erratic behaviour has gone completely,
> > however, I am still facing the problem whereby one of the pots only
> > gives a range of  0-225 (ie. using the applesoft joystick test). BTW,
> > this was the pot that I did not "manipulate" the internals of
> > (hmmm....maybe I should).
> >
> > Is there any easy way of fixing this, or is this the problem of
> > linearity that you mentioned is hard to fix?
>
> No, a range of 0-255 is exactly what you should see from a device
> whose output is represented as a single 8-bit byte.  ;-)  The Apple
> will respond to any resistance greater than a certain value (near 150K)
> with a time measurement of 255.
>
> That means that you are getting the full range of resistance (and maybe
> a bit more, since 255 is probably reached before the stick reaches the
> end of its travel).
>
> > I imagine most games would function OK with this range, however, the
> > game I tested it with (Sensei) did not respond to downward movements
> > (ie. moving the stick in the limited 0-225 axis). I read that you can
> > counter this when converting an IBM style joystick by introducing a
> > capacitor to increase the resistance somehow. Would it be possible to
> > do something similar here to increase the range?
>
> What you describe is a centering problem, not a range problem.
>
> Any value below 128 (or so) (or above, depending on which way the game
> expects the stick to work) will represent "down", just as the opposite
> side of 128 will represent "up".
>
> -michael
>
> New, faster SUDOKU v2.0 solver for Apple II's!
> Home page:  http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."

Michael,

I think you mis-read my previous post - I am getting 2-2-5 not 2-5-5
from one of the pots. They kinda look the same so it would be an easy
mistake to make....  ;-P

So I am not getting the full 8 bit range.

thanks,
-p