Introduction: DIY TI-99/4a Composite Video Cable
Being the type of guy that is very much into retro technology, I find it hard to pass up a good deal on vintage electronics. Recently I came into the possession of a second Texas Instruments TI-99/4a computer.
Having one with lots of bells and whistles, I decided I would turn this particular computer into a loaner unit for a friend who works as an IT Director. Since he likes to toy around with retro tech as well, I figured this would be the perfect opportunity for the two of us to collaborate on coding projects. There was only one problem...
The TI that I got such a good deal on had no power cable, or video cable. Bummer... But that shouldn't stop someone from getting this beautiful piece of technology up and running. I decided to start off with the video cable. So off to the forums I went. Specifically, http://atariage.com/forums/
There I found several threads dealing with the topic or pinouts. But mostly what I found was a good supply of people who either didn't have the basic tools or skill to make a video cable, or simply just wasn't comfortable in doing it.
This article is for the second group. I hope someone in the future will benefit from this and get that classic machine running once again.
Step 1: Required Components
The items needed for this build are pretty simple.
Composite A/V Cables
A little confidence
The are only two physical items needed to make this cable. But the last one may be the most important. If you've never done any type of hardware modification, things like this can seem intimidating. Trust me, it's easy. Just have confidence in your ability to make it happen.
I think sourcing the cable should be very self explanatory. And the DIN-5 plug can be purchased on one of the various online websites, or auction sites if that is what you prefer.
Step 2: The Basic Tools
The tools needed are very basic. And they are items that most people will have on hand, or can buy from the local big box store for a few bucks. If you don't have an item, buy it. These are very basic tools.
A pair of side cutters
A pair of needle nose pliers
A soldering iron
Electrical Solder and Flux
For the purpose of this article I am using Rosin core solder. It has the flux in the core, and requires no extra flux to make a good joint. However, if you choose to use something else just make sure it's for electrical use.
Step 3: Disassemble the Plug
These plugs are a four piece design and come apart with little difficulty. Simply push the black rubber/plastic piece back, and pull the metal tube out. It will come apart in halves, revealing the inner most piece. This is where the work will take place.
Step 4: Clip & Strip!
First things first, clip the ugly end off of the cable. We're going to make it prettier by giving it a new face!
Next, strip those wires to reveal the ground shield and the inner wire.
Afterwards, remove the foil from around the wire, and lastly strip it back a little. You'll want to do this for all three wires.
Step 5: Soldering
This is the part that everyone seems to worry about. Let me say this now, this is easy. But there are tricks to make things easier.
First thing you'll want to do is to slide your plastic outer shell over the wires. Depending on their thickness, it may be loose or snug. Don't worry, this will be solid by the time we're done with it.
Afterwards, you'll want to twist the red and white wire to make a temporary connection. Do the same with all three ground shields. They'll be connected together, and we want to make sure they hold tight.
The next thing you'll want to do, and possibly the most important, is to tin your wires and the cups of the connector. On the connector it has three cups you'll want to tin. If you're looking at the back side, the side you'll solder, with the pins on the bottom, you'll (from left to right) want to tin pins 1, 3, and 4. To say this another way, the top left, the bottom, and the pin just to the right of the bottom pin.
Tinning is easy. If using a cored solder, simply touch your iron to the wire or pin. After a moment, begin feeding solder to it. Once it begins to stick, rub it in with the iron, and you're done. If using a difference type of solder you may need to apply the flux to the part first.
After the tinning is done, position the first wire to be soldered vertically over the back side of the plug with the pins pointing up. Touch the iron to the pin, and press the wire down into the cup light. Pull the iron away, give it a moment to cool, and check to make sure it is soldered. Now do the same for the other wire, saving the ground for last.
The ground takes a little more solder to make a good joint. But once you get a little on there it holds nice. You can then add a little solder to the joints to stiffen them up if necessary.
Step 6: Protecting the Computer
As an extra precaution, I like to add a little bit of liquid tape around the freshly soldered wires to make sure that they do not short out. Especially considering that the TI has one of those pins at 12v DC. It could easily get your system, or at least the video chip, and possibly your TV.
After it dries, you'll want to fit the two piece metal housing. There are keyholes in the housing for pieces of the molded plastic core to slip into. Once in place you'll want to use a pair of pliers to pinch the clamp down around the cables. This will ensure that if the cables are pulled it won't break your solder joints.
When you're done, replace the second piece of the housing and slide the rubbing casing back into place. You're almost done!
Step 7: Testing the Cable.
Provided you followed the steps completely, you should be ready to test your cable. Plug it in, and turn it on. I bet you'll see something similar to the picture above.
If not, go back and check your work...and check to make sure the TI is plugged in. Sometimes we forget, right?