The graphic file that purports to be the
internal schematic for the CoCo Max Hi Res
Joystick Pack contributed by Randy Poppe does
indeed provide a circuit for modifying a standard
Tandy Hi Res pack that will result in its working
with CoCo Max 3.  However, this "crack" of the
hardware is imperfect in two ways.


The Problem:

    Randy never approached analyzing the pack in
the proper way, that of removing the epoxy using
methylene chloride-containing paint remover. 
Indeed, the analysis that led to his "crack" was
done by chipping away the epoxy cement using some
hard tool.  The problem was that Randy failed to
discover a second resistor used by Colorware that
modified the scale of mouse response.  

     Thus, those using Randy's crack will find
that movement of the mouse needed to move the
cursor from one end of the screen to the other is
about HALF that when a genuine CoCo Max 3 pack is
used.  While (as noted above) Randy's carck DOES
result in a working CoCo Max 3 hi res pack, the
responsiveness of that pack is substantially
CRUDER than the responsiveness of a genuine CoCo
Max 3 pack.  


The Solution:

     Add a 560,000 ohm 5% tolerance (green, blue,
yellow, gold) resistor in PARALLEL with R7.  R7 is
in most packs originally a 390,000 ohm 2%
tolerance resistor (orange white yellow red)
located next to the cylindrical electrolytic
capacitor C2.  Adding the 560K resistor changes
the scale of respnose of the CoCo Max Hi Res Pack,
and results in more fine control.   Note that this
added resistor is ONLY for use with CoCo Max 3,
and must not be in the circuit of the hi res pack
when it is used with other programs.  

     Randy also for some reason recommends using a
2.2K resistor between pin 6 of the joystick plug
and ground.  This is his added resistor "R9".  I
am not quite sure why he picked this value, for in
the actual Colorware CoCo Max 3 pack that I
analyzed the resistor that they used was 15K. 
Purists might want to make the substitution.


   This little addendum corrects all of Randy's
mistakes.   

   Despite his imperfect "crack", Randy deserves
credit for being the first person to widely
distribute a schematic for Hi Res Pack mods that
DO work.   

   ---marty



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