FISHERS (project pt.6)

 -PREPARING THE ENCLOSURE:

Prepping the keyboard enclosure is a lot of busy work, and gets very messy from all of the plastic chips, dust, and sometimes smoke. It is always a good Idea to clean up the work area first, and have my HEPA vacuum and smoke absorber at the ready. Wearing eye and respiratory protection is essential, too. It is really not fun to try and pick little plastic bits out of breadboards or parts bins, so putting things away before starting is crucial. 

Giving the enclosure a good scrub with soapy water is a good start in getting things cleaned up, and will make it easier to spot the stains and blemishes that will need extra attention with rubbing alcohol and a scrubber. Removing the stickers from the keyboard was especially challenging. The adhesive is very stubborn, and after trying to heat it up to release it, and finally scrubbing with alcohol, the only thing that seemed to finally get it off was a fine grit sanding block that left a slight buff to the finish, but is hardly more noticeable than the difference in color of the rest of the case–to the strip of plastic that was protected from sunlight for the last 37 years. 

A lot of the inside of the top piece needed to be removed to make room for the new circuit boards and added hardware. Throughout the case there are several lateral-type braces and walls to help shore up the structure of the enclosure. I simply twisted and pulled a lot of them out where needed with some flat pliers that work perfectly for this. In more difficult areas, I use my trusty Dremel tool with a 1.5mm tungsten carbide end mill bit that chips through plastic with ease, but can get pretty messy, fast. 

I had to do some fine trimming around the front of the keys to make a space for the capacitive touch keys. Originally I had thought it would be better to use small 3mm metal brads as the touch points, but I somehow misjudged when drilling the holes through the case, and the circuit board was unable to reach the holes I drilled. Instead of using the 3mm brads, I extended the holes and used 10mm brads to cover up the mistake. They look and work fine, but because of their size and profile, they are much easier to touch mistakenly. The sensors are already pretty sensitive, and they self calibrate on power-up, so the whole area of the 10mm brads are a little more responsive than I would have liked. 

The top face of the enclosure has raised plastic lettering for the sharps/flats above the keys, and the names of the button switch functions on the right hand side. The speaker grill is also raised plastic. The top face of the enclosure needs to be flat so that the faceplates can be mounted to it, so I used a flush-cut saw to carefully knock most of it off, then used a fine grit sanding block to flatten everything down to a flush surface. I had to be careful doing the sharps/flats since the plastic area near the keys would not be covered up by the faceplates, and any scratches or marring would be painfully visible.

In order for the hardware on the circuit boards to pass through the enclosure, I needed to cut out cavities in the top. In the past, I have just cut out huge sections to let the entire circuit board area pass through, but rather than doing that and potentially weakening the strength of the enclosure, I decided to try and see if I could get away with just drilling dozens of oversized holes that the hardware could pass through, leaving the surface of the enclosure more or less intact. It worked out in this case, but the joystick section needed to be mostly cut out since there were so many odd features in the plastic like the speaker grill and the button-switch holes, that it made it impossible to drill all of the holes I needed.

To locate all of the hole taps that I would need to drill, I drew up a guide that matched the perimeter of the faceplates, and created a template with small center taps for the holes printed on it, and the diameter that the holes needed to be cut to. I used my laser cutter to engrave and cut the templates out of cardboard, then taped them all together onto the enclosure. I then drilled all of the holes with a 2mm bit, then removed the template and used a stepped bit to cut the holes to their required diameter. Cutting the holes slightly larger than they needed to be allowed for slight movement in all directions, which I new would be important when fitting the circuit boards to the enclosure. This is also why I held off on drilling the faceplate mounting holes until I was sure that everything lined up with a dry-fit. 

For the joystick and speaker section, I used my Dremel again to cut out the large cavity for the larger parts. I had to go back several times dry-fitting and re-adjusting positions to get things to line up–fine tuning holes here and there with files and Xacto knife. The enclosure's screw-post standoffs were hard to work around even though I gave myself extra space in the circuit board design. Unfortunately it wasn't enough space to move the circuit boards where they needed to go, so I had to grind and chisel the posts in from the sides to get clearance.

With everything fitting into place, I engraved and cut some temporary faceplates out of cardboard that I could use for prototyping. Using thin cardboard makes it much easier to debug since they are lightweight and flexible, and if they get damaged that's OK. They really just need to hold everything together and indicate the functions while wiring up the circuits and testing everything out. I can also write on them if I need to.

Part 7 coming soon...