A85: How to replace TI-85 link recepticle.

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A85: How to replace TI-85 link recepticle.

How can you fix a broken link port (in as much detail as possible)?  I need
mine to be fixed badly?

[Jan Zumwalt]  There seems to be a lot of interest in this, and it is
obviously the Achilles heel to the TI-85. I will answer this as a FAQ and
hopefully it will get posted to TICALC.ORG.

A few pointers first. You can take the calculator completely apart if
necessary and make repairs safely. A friend of mine spilled juice on his
and completely cleaned all the parts. He then deliberately installed
the "ON" key and "ENTER" key upside down just to play with peoples minds.

TI uses SMT (surface mount technology in the production of this calculator
which ordinarily requires special solder paste, applicators and 
soldering/desoldering technique. However, this particular part is readily
accessible and uses extra large solder pads so standard transistor/IC 
soldering techniques can be used.

Parts: 30 watt pencil iron or soldering station, 10" .031 (21 gauge) 60/40
resin core solder, 1ea 2.5mm female miniature receptacle, and patience. 
 
1) Remove the AAA batteries and unscrew the two screws at the bottom of the 
   case. Remove the third screw holding a metal plate over the button 
   battery.

2) Gently pry the two plastic halves of the calculator case apart with the
   blade of a medium flathead screwdriver.

3) The calculator will look like the drawing below. Locate the three solder
   pads directly next to the receptacle (the 1,2,3 in the drawing).


               /'\
                |
                |
        .      top     .
        .              .
        |              |
        |              |
        |              |
        |  ..........  |
        |  .        .  |
        |  . battery.  |
        |  .  area  .  |
        |  .        .  |
        |  ..........  |
        |              |
        |              |
        |              |
        |      ,1      |
        |      ||      |
        |     2||3     |
        \------==------/

4) Using a jewelers screwdriver apply moderate pressure to the receptacle and 
   apply quick heat to the pads in rotation until it lifts free.  
 

5) Resolder the new miniature receptacle to the pads making sure that the 
   connections are correct as shown below


---------\
          '--------\/\
          | 3 | 2 |  1> 
          .--------/\/ 
---------/

6) If you have a multi-meter, check your connections with a plug inserted.

7) reassemble the case by snapping the plastic halves together and replacing 
   the three screws. Replace batteries and your done.

                
Note: TI uses an unconventional male plug that may cause problems if you are
making a cord with the factory receptacle. The problems is the 2.5mm jack 
used by TI MUST have a smooth barrel. The common ones available at Radio 
Shack have a detent that helps hold the jack in but WILL SOMETIMES NOT MAKE 
CONTACT in the TI female socket. The TI female just uses raised bumps in the 
barrel for contacts while the walkman style has metal fingers that project down.

I ended up cutting my TI link cord in half and splicing onto it.  I looked in 
Newark and Allied for the proper jack, but found none. If I find the proper parts,
I will order two dozen or so for other people. If someone knows where or how I
can get these parts, please e-mail me. 

--------\/\
   |   |   >  Walkman style jack     /---  Walkman contact
--------/\/                       \_/

-----------                        _  _   TI contact
   |   |   >  TI style jack         \/
-----------

Jan W. Zumwalt
zumwalt@alaska.net
http://www.alaska.net/~zumwalt
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