The first thing I wanted to fix is the weakest spot of the C16, that is the joystick ports: these pretty much directly expose pins of the TED to the outside world, which means that they are a likely entrance door for electrostatic discharge to destroy your precious chip.

Now that I think of it, this might be one of the reasons why Commodore switched to the MiniDIN ports, shamelessly breaking compatibility with the Atari joystick standard: the MiniDIN ports are female and their contacts are recessed, which makes it (slightly) less likely to touch the pins with your fingers while poking around your computer (note that the power and reset buttons are very close!), at least compared to the DB-9 male ports that the Atari standard uses.

Anyway. this is what encouraged a nice guy named Levente Hársfalvi to come up with the design for an adapter that, besides converting the MiniDIN ports to DB-9, interposes a buffer IC between the TED and the actual port, providing some protection. It is this design that I used in my OpenC16JoyAdapter adapter.

Now that we have a lot of free space on the mainboard, why not put these adapters right inside the machine? Here's how we can do it:

The circuit is pretty simple and placing the new components on the board and routing the tracks was not as terrible as I had anticipated, this is what I ended up with:

I had to move some of the ferrite beads for the keyboard lines and a few more things, but I think it came out pretty clean. I think we can even do a bit better, but we'll leave that for later.

Now our TED will be much safer. We could also go the extra mile and replace the infamous Mini-DINs with DB-9 connectors, This would have a few implications, most of which sound good to me. I'll think about it... Feel free to have your say in the comments!