Atari Controller Test Rig « modelrail.otenko

16Jun/200

Atari Controller Test Rig

Long-story-short, I've got a new night-job, bringing a large quantity of Atari-related paraphernalia back to life. I've done it before with the 2600 Jr, and I'm ready to do it again, and again, and again, with this batch.

First up is a box of gamepads and controllers. My initial plan was to get one of the Atari units in a known-state, and then test the controllers from there... but that could lead to issues if the console wasn't actually 100%. Instead, why not just rig up a DB-9 port to a simple 5v LED circuit to test each button?

Google will produce a crap-load of results for Atari Joystick Pinout, so find one of them and get started. I chose this one. It turns out the controllers are very straight forward... they just act as a conduit to ground. Pin 8 is the common ground wire and all buttons (directional-pad inclusive) just join their respective pin to this wire.

The above rig was therefore constructed. Voltage is supplied from my desktop power supply and a miriad of LEDs were selected from the junk box. A selection of 48ohm resistors tie them all to the 5v rail. Their anodes all go to a respective pin on the controller port... starting with Up, Down, Left, Right, A, B from the left-most green LED. Of course, A and B are contentious, as the 2600 only utilises one fire button. Even better, the DB-9 socket also supports trigger, so that's the clear LED placed awkwardly on the left-hand side.

First controller to be tested was an Atari gamepad and it instantly misbehaved. Upon opening it, I found that both A and B buttons were tied high with resistors.

A little googlin' declares that these gamepads are actually for the Atari 7800, which supported two buttons. They've nicely made them backwards compatible though, allowing either button to be the standard button for the Atari 2600 jr. Regardless, those pull-up resistors meant that my A and B button LEDs were always dimly-lit!

Upon pressing either button, their respective LED fully-lit, and so did the left-most trigger LED. This makes me think that trigger is the actual 'button' for the Atari 2600 Jr and A/B are for newer systems. Regardless, the unit still had an issue. For those keenly-observing the photos up until this point, you'll have guessed that the directional pad's right button was crapola. It worked sometimes... and then it worked all the time when you jiggled the cable at the entry-point to the controller. So, what to do? Truncate!

Take a good length off, away from the game pad. Cable fractures, when entering casing/housing, are a very standard thing. Usually, very much like this unit, there's 'protection' inside the casing where the cable is held in-place to prevent it from being wrenched out and putting pressure on internal components. This 'protection' in this case is a zig-zag of pins to hold the cable in place without putting serious pressure on it.

For this unit, this 'protection' has done its job and kept the internals safe, but the cable has instead formed an issue directly after it exits the controller case. Here, thanks to humans like me, waving the controller around (rather than pressing the correct buttons), causes undue stress internally and ruptures the wires. In this case, it actually severed the wire that conducts a directional-right press.

As above, strip the newly truncated cable and tin all ends. Once done, de-solder the original chunk of cable, re-soldering the newly cut ends in the same order. Make sure to keep the white bridging wire between both PCBs. Finally, run the cable through the zig-zag and hold it there for a bit to make sure it understands its new role. If you just place it and let go then the cable tends to want to return to it's standard straight-line form. It's actually tough for a thick cable to make those curves, but as mentioned above, it's for the sake of the guts of the contorller.