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Second prototype: the case

Building a nicer case than the one for the first prototype was a small project in itself: the positioning of all the items is not self-evident, and finding a way to mount the front panel items without polluting the front with screws and nuts also took some thinking.

First of all, we make the sidewalls of the case. They are pieces of 12 mm thick MDF, with grooves on the sides where the horizontal and vertical pieces meet, and also grooves on the front and back along the long side, in which the front and back panels will slide. Making the grooves is precision work that took a few iterations to get just right.

The back is 3 mm thick MDF board. It will also be the place where the PCB will be mounted, so we have to glue two supports to it that can hold the screws for the PCB without going all the way through.

This is the PCB mounted to the back panel.

Next up is the front panel. We do this in two layers, because working with one layer would require drilling holes and having screws and nuts on the outside. The outside panel is 3 mm MDF, like the back panel. The inside panel is 6 mm MDF, in which we will make holes to mount the potentiometers and the speaker.

As you can see, we used the routing tool to take away about 3mm of thickness in the area around the speaker, to catch the flange of the speaker in a press-fit with the outer front panel. The on-off switch/volume pot meter area receives the same treatment, so that the retaining nut for the switch/potmeter can be mounted flush with the surface of the panel.

The sliding potentiometer for tuning is mounted on a piece of PCB, which in turn is mounted from the back onto the inner front panel. The sliding potentiometer doesn't have any "mechanical" way of being mounted, so using PCB is the only option.

The outer front plate is decorative, so it was made with some extra care. The routing tool was used to make all the openings, for maximum "straightness" of all the grooves. The groove for the slide potentiometer is 3 mm wide (smallest routing bit I have), so only the handle protrudes. The hole for the on-off/volume switch is also just large enough to allow the shaft to come through. In the middle is a circle-shaped area with 6 mm wide, horizontal grooves. Initially I wanted the grooves to be 3 mm wide, but I couldn't think of a good way to do this while making sure all the grooves would be straight. This will be something for version #3 of the case.

This is the case with all the electronics mounted in their intended places. I left the wires long enough to be able to dismount the case without having to pull on the wires.

The final result looks like this:

Not bad for the second try! Some points for improvement though:

  • Paint the MDF, or use a nice type of wood that doesn't need treatment to look good.
  • Think of nicer way to make the speaker area. Possibly use speaker cloth on the inside somehow.
  • The battery compartment needs some thinking. Currently the batteries are on the inside, so the case has to be opened to get at the batteries.
  • Find a good way to mount the antenna.