Well, what happened in step 3 was a series of oversights on my part. Ultimately the reason my first version of the contact disks didn't work is that they weren't thick enough. The disks that I made using the craft foam ended up being a little over 2mm, or 1/8" of an inch, which apparently is not thick enough. I discovered this because I wasn't feeling anything at the end of the keystroke. There should have been *some* kind of bottom resistance when the contact disk touched the PCB, but all I got was the hard plastic-on-plastic of the key bottoming out in its spring.

So foo...what to do? Well, in a fit of desperation, I simply super-glued two disks together and put that into one the keyboard switches. That worked!

Well, kinda. I was getting a lot of duplicated or random characters. For example, if I tried to use the 'a' key, I would get a string of random characters. It was never consistent and could contain even non-text characters like CTRL. Because there was no pattern I made the assumption that it had to be the way I had assembled my experimental double-sandwich stack. I suspected that perhaps because it is a capacitance sensing keyboard, the double-sandwich method was causing some kind of capacitor effect? So I went forward and created about a half-dozen of the double stack disks by simply doubling up the foam, rather than just gluing two sandwiches together. I put version 2 of the craft foam disks into various spots on the keyboard and gave it a whirl. Annoyingly this did not help. The keys were triggering reliably (meaning the foam thickness was good) but they were producing random characters. Not exactly my definition of success. And on top of it all, I was getting very inconsistent key press requirements depending on the placement of the disk, indicating that my materials choice or disk diameter was probably wrong.

Something had to be done.

So at this point I decided to try making a set of disks out of the same foam that Compaq used originally. Based on the previous disks, I figured that they had used polyethylene foam, probably light density, and probably around 1/8". Measuring the old ones proved extremely difficult, as they didn't stay intact through the measuring process. Near as I could tell, they were a bit over 1/8".

Now, a side note about foam. Ah foam. What a pain. I knew what I wanted, but had no idea what it was called! I'm sure there's someone in the foam industry saying that the types and materials and densities are all very different and I'm an idiot for getting them confused. Well, let me tell ya this, I didn't know my polyethylene from polystyrene from polypropylene. All I knew was that I wanted that light grey squashy foam that you sometimes get at the bottom of a box of stuff from electronics vendors. It couldn't be too stiff, it couldn't be too light.

So I tore my house apart, thinking that I must have a sheet of it somewhere. It's one of those materials that you're pretty sure you have laying around but you can't be sure where you last saw it. The basement? Nope. The office? Nope. At work in that junk closet? Nope. Well, apparently I don't have anything even remotely like it, because I still have yet to see anything like this foam just laying around. Oh sure, I had thick stuff. Like 1/2" or larger, but nothing smaller. You could cut the foam thinner, but that seems like it would be a major pain. And even if I did, I certainly didn't have any that was new enough that it would be worth carving up to use in a project. It could disintegrate next year for all I know. I needed new stuff that's the exact size.

So I started digging around on the Internet thinking SOMEONE must sell this kind of stuff. McMaster-Carr? Nope. Amazon? Not as far as I can tell. ULine? Nope, nothing this small. Finally I came across a company called Foam Factory Inc. They had exactly what I needed. I actually ended up buying a few different types, but ultimately what you want is 1/8" closed-cell polyethylene foam in the 2 lb density. This...