TI99/4A Computer and Joystick Adapter

Recently I scored a great TI99/4A Home Computer plus games from eBay. There are some really good games on this 8bit micro, and luckily most can be picked up relatively cheaply.

The item was pick up only, and in another state. Luckily I had a mate visiting that same area at the time, and he was able to pick it up for me and bring it back in his luggage. How is that for service!

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The only bad thing in my opinion about the TI99 is the terrible joysticks! So after a clean up of the unit, the first task was to make a joystick adapter allowing the use of standard sticks, such as the Atari 2600 controllers.

So pictured below are the terrible sticks. You can’t see this in picture, but the 2 joysticks are connected to a single D9 plug hence the need to make an adapter.



There is plenty of information available online about how to make an adapter. I chose to follow this one http://www.mainbyte.com/ti99/hardware/cables/joystick.html due to its quality diagram (pictured below).


Diagram from http://www.mainbyte.com/ti99/hardware/cables/joystick.html


My goal was to make a little case for the adapter, making it nice and neat. Starting out with a piece of stripboard, I cut most of the traces on the back for placement of the diodes. I also cut a couple of holes into the single strip on the right because the scrap stripboard I used I needed another connection.



Soldering in the diodes is so easy. essentially just connecting 2 diodes together the anode end and having the cathodes separated. There are 2 diodes per input (left, right, up, down, button). Some people don’t even use diodes when making these adapters, but I assume that when using 2 joysticks at a time they are needed.



Now soldering a DB9 connecter and length of cable to the stripboard.



Time to make an enclosure for the adapter. I use painters tape to mark out where the cuts need to go. Then use a hobby drill to roughly cut out within the area. That allows use of a needle file set to carefully file away and make a neat job. Seriously I recommend investing in a needle file set for this work, they are cheap. I have seen many projects online with rough cutouts – there is no excuse.

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Now have cut and measured wires to connect up the joystick ports of the adapter.



To connect the base of the enclosure to the stripboard I use 3M double sided tape. I don’t know how long it lasts exactly, but I do know that cheap no name double sided tape goes brittle and loses its adhesiveness much quicker.



Now the icing on the cake is a nice printed label.



Parsec – a great game on the TI99! Much better with a different joystick.



Lets finish off with a few random TI99 photos I had on my phone. One thing to add is the TI99 has very good quality RF. Can’t really tell from the picture below though. I really need to get hold of a speech module now!

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