From: foegelle@ccwf.cc.utexas.edu (Michael Foegelle)
Newsgroups: comp.sys.apple2
Subject: Atari 5200 Trak Ball modification
Date: 27 Aug 92 15:42:25 GMT
Distribution: comp.sys.apple2
Organization: The University of Texas at Austin, Austin TX

From the volume of responses I have received following my mention of
converting an Atari 5200 trak-ball controller into a working track ball
for the //e (to be used with the //e mouse card) or (I assume) the //c,
here's the dope on how to make one.

For starters, where to get the controller itself...  I ordered mine
from:

   Alltronics
   2300 Zanker Road
   San Jose, CA 95131

   Phone:  (408) 943-9773
   FAX:    (408) 943-9776

It's an Atari Trak-Ball controller (model CX-53) for 12.95 + S&H, but
don't tell 'em how much you heard it was for unless they quote something
higher, because you might be able to get it for less.  (Me and my big
mouth, when I called I coulda saved, $2 if I'd have kept it shut!)

Okay, on to the modification:

If you pull the five phillips head screws from the bottom of the
cabinet, you'll be able to open it up easily.  Be careful when opening
the case.  If you do it while it is still upside down, the 'cue ball'
will remain in the opening and the two encoding wheels which the ball
sits on will fall out.  That's no big deal, but be careful not to damage
the wheels or lose the bearings.  If you flip the case upright and then
remove the top, the cueball should remain sitting on the wheels and
you'll be able to see just how everything is mounted and how it works.
(As well as how it has to go back together again!)

Now that you're inside, the first thing to do is remove the ball and the
encode wheels with the bearings and set them aside out of the way
somewhere so that they won't be damaged.  (It's probably a good idea to
balance the encoder wheels on one end so that you don't warp the wheels
themselves.)

Next, slide the cable connectors off of both the trak ball circuit board
and the button circuit board and remove the cable.  (You may want to
chop the connector off the end and use the cable to connect your
modified track ball/mouse, that's up to you.)

Next, remove these four chips (CD4538, CD4030, CD4011, and CD4013) from
the triangular shaped track ball circuit board by carefully prying them
out with a screwdriver.  (These are static sensitive chips, so if you
want to keep them for possibly use in the future, take steps to
eliminate static charge (like you would on your computer) and wrap them
carefully in tin foil or put them on an anti-static mat. Care should be
taken with the circuit board itself too to avoid zapping the one chip
you left in.)  If necessary, the circuit board may be removed from the
casing by carefully prying back the plastic finger holding the lower
left corner of the board down.  Be careful not to break the finger off.


     _____________
    | <12345>     |                                 KEY
    |          XX |                                 ---
    |          XX |                                 [chips]
    |          XX |                                 XXX - opto sensors
    |             |__________ <connector>
    |                        \__
    |                           \__
    |   [CD4538]   [CD4030]        \__
    |                                 \__
    |         _                          |
    |       _/ \_                        |
    |      /     \                       |
    |      \_   _/                       |__________
    |        \_/        [CA339]                     |
    |                          \          XXXXXXXX  |
    |   [CD4011]   [CD4013]     this one stays      |
    |                                               |
    |_______________________________________________|


The CA339 is a quad comparator which just amplifies the signal from the
opto sensors.  The next step is to just make the power connections and
the necessary connections to the output of the CA339.  My suggestion
would be to get a 14 pin dip header and use it to make the connections
so that you can always unplug the board without changing anything.  The
connections will be made in the socket labelled "CD4030" above.  Pin 1
is the lower left pin in the socket.  You'll be connecting to a male
DB-9 connector for the computer side:

                                             DB-9 connector
 14  13   12  11  10   9   8
 ----------------------------           -----------------------
|                            |          \  5   4   3   2   1  /
|    CD4030 socket           |           \                   /
|                            |            \   9   8   7   6 /
 ----------------------------               ----------------
  1   2    3   4   5   6   7


    CD4030 socket      Signal description      DB-9 mouse connector
    -------------      ------------------      --------------------
      pin #  7              Ground                 pin #  3
            14                +5V                         2
             1               Right                        5
             2                Left                        4
            12                 Up                         9
            13                Down                        8
        ------              Button                        7


 (Note:  Pins 4 and 5 of the five pin connector can also be used as the
power connectors, with pin 4 as +5V and pin 5 as ground.)

The only remaining connection is to make the button connection.  I used
the innermost red button as my mouse button, although you could use
either or both.  On the upper circuit board, pin 1 is the pin nearest to
the center of the circuit board.  Pin 3 should be connected to ground
and pin 2 is the button connection (connect it to pin 7 of the DB-9
connector).

That's it!  That should be everything needed to make the trak ball work
as a mouse on your //e.  Carefully snap the track ball circuit board
back into place if you removed it.  Make sure it is sitting properly on
the alignment pins and that the plastic clips are holding it down
firmly.  Then place the encoder wheel rollers into place, making sure
that the bearings are properly in place and that each wheel rides in the
slot in each opto-sensor.  Spin both making sure they spin freely.
(They should spin for up to ten seconds before stopping.) If the
rollers are placed properly, you may then set the track ball on top of
the mechanism so that it rests on the center of each roller and on the
third 'caster' bearing mounted on the plastic pole which sticks up
through the center of the circuit board.  Before closing the case you
will probably want to plug the trak ball into your computer and test it.
A short circuit of the power supply would be bad for the computer, but
any other bad connections wouldn't hurt anything other than possibly the
track ball circuit board itself, so you aren't likely to lose much even
if you screwed up the connections.  If the connections are all okay, it
should work fine at this point.  If so, just put the cover on the case,
flip it over and install the screws.

If there is a problem, double check your connections first. The only
other change that may be necessary would be if the LED's in the
opto-sensors aren't receiving enough current for them to operate
properly.  I had this problem with one of the sensors on mine.  The way
to correct the problem is to replace the current limiting resistor with
a smaller one (or put a smaller one in parallel).  I'd have to retrace
the circuitry, but I believe the limiting resistors for both sensors are
the two right beneath the horizontal (lower) opto-sensor. (There are
two vertical rows of three resistors; they're the top resistor in each
row.)  The current values are 230 ohms I believe, and I used a 100 ohm
one on the one I replaced and it all works fine.  Again, hopefully you
won't have to make this modification, but you never know.

Finally, if you really want to have this trak ball, but feel you just
aren't up to making the modifications yourself, I'll make this offer for
a limited time.  I will make the modifications for $25 + parts + S&H.
That will probably work out to $45-50 but I'll verify that it works
properly on my //e and make all necessary modifications.  If you're
interested, E-mail me at "foegelle@ccwf.cc.utexas.edu" to arrange it.

And just so that you have some idea what you're getting into if you've
never seen the Atari 5200 Trak-ball, it's a black case approximately 9
inches by 11 inches by 3 or 4 inches tall with a sloping face.  The trak
ball itself is a large (2.5-3 inch) ball in the center with two red
control buttons on either side (the inner one becomes the mouse button
with the above mods.).  Above each pair of control buttons is a rubber
numeric keypad laid out as a telephone keypad.  (These could be modified
to work with the numeric keypad input on the //e, but that's a subject
for a later project!)

Well, I hope that is enough to help you figure out how to make the
modification, 'cuz that's all I'm going to type!  Enjoy and good luck!

Michael Foegelle

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   Michael Foegelle  |                    |   foegelle@ccwf.cc.utexas.edu
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