cx80 Modify a CX-80 Trakball to have two working buttons?

[Lando242]

I picked up an old CX-80 Trakball, which I've heard was intended for the 8-bit computer line, a while back but had no good use for it. I then bought a 2600-daptor D9 so I can use some vintage controllers on my PC when playing emulators. I have found the trackball to be excellent for games that used a trackball originally, especially in MAME. Being limited to only one button is kind of a pain though. Is it possible to modify one of the buttons, which are duplicates for ambidextrous control, to be a separate button and still work through the 2600-daptor D9?

[Lando242]

After further research I found an interesting kludge. It seems it was not unknown to modify these old trakballs to function as a mouse on the Atari ST or Amiga. The 2600-daptor D9 supports the Atari ST and Amiga mice out of the box. This only requires running 4 new wires from one of the chips in the trakball. The specific instructions I found said to use pins 2,4,10, and 12 off of the 14 pin IC on the bottom right of the PCB. This was with the PCB removed from the unit, and flipped over so components are facing up, and the wires going to the cord sticking out the top. Disconnect the Red, Brown, Orange, and Yellow wires from the PCB and extend them so you can connect them to pin 2 (red), pin 4 (brown), pin 10 (orange), and pin 12 (yellow) on the IC. The trakball should now work as an ST mouse. You just need to swap the wiring around a bit to make it an Amiga mouse but I didn't look into that any further. Please note that I have NOT TESTED THIS. It is going off of a guide published in 1991!

 

Sadly, to get an additional button requires replacing the original cord completely. Atari only put 7 wires in the trakball's cord, as that was all that was needed. So, pins 5 and 9 are empty on its connecter. Pin 9 would have been for button 2 (ST and Amiga mouse) and pin 5 for button 3 (Amiga). If I decide to go that far, it should be a fairly easy mod. The wires coming from the power cord use a weird kind of spade connector and just clip onto the PCB. So, get a cord that has additional wires, connect the main ones up where needed, scratch the trace going to the second button on the PCB, and wire it to pin 9. Furthermore, you could install an additional button and wire it to pin 5 and the ground for a third button for use on the Amiga. You could even install a selector switch to swap between trackball and mouse modes if you wanted.