I’m making progress on building BMOW’s case. After more than a year of sitting naked on my desk, it’s finally going to get a proper enclosure: a gutted X-terminal that is just the perfect size… or so I thought. A couple of weeks I ago, I used a Dremel to cut out a divider that partitioned the interior space. Then this past weekend I did the first test-fit. Uh-oh! While the BMOW board did just barely fit inside, the lid wouldn’t fit on with the board in the enclosure. It was actually both too wide and too tall, by just a fraction of an inch in both dimensions. Doh! Here’s what the test fit looked like:

The lid (not shown here) has small tabs that extend into the case, and fit into grooves in the base. These tabs were bumping into the BMOW board when I attempted to close the lid. That’s not surprising, since you can see in the photo that there’s virtually zero extra space horizontally. In fact there’s about 1/16 inch of space to spare on both sides, so I cut the tabs down to that size with the Dremel, and now they just barely squeak through.

I wasn’t out of the woods yet, though. The lid still wouldn’t close, because the board was just a fraction of an inch too tall. Putting a ROM in that green ZIF socket you see in the photo was just barely enough to prevent the lid from closing. After some thought, I decided to solve that problem by using shorter standoffs underneath the board, so it would sit lower in the case. That was easier said then done, however, because the wire-wrap pins on the bottom are about 3/4 of an inch long, so the standoffs need to be taller than that. I found some standoffs that worked, but now those pins came so close to the bottom of the case, that they actually made contact with the jagged remnants of that divider I’d previously removed. I had to go back and grind the divider down to a nub with the Dremel before it all fit.

The next problem I faced was how to anchor the board securely in the case. Drilling mounting holes for the standoffs would work, but I don’t have any way of measuring and drilling the holes accurately enough to match the holes in the board. In the end, I decided to screw the standoffs into the board, then stick the whole thing in the case and hot glue the standoffs to the case’s base. This had “bad idea” written all over it: there was a decent chance I might accidentally melt or glue the the board itself while anchoring the standoffs. That was risky enough, but it gets worse. You can see in the photo that I had good access to the top and side of the board with the glue gun, I couldn’t really reach the bottom side. Unfortunately BMOW has only two mounting holes on the bottom side: bottom-left and bottom-middle (hidden under the cable in the photo). I actually dragged the whole thing down into the basement, and drilled a new mounting hole in the bottom-right of the PCB with everything still mounted on it, and the whole thing in the case. It was a little comical. I covered all but that corner with a towel to protect it from flying metal flakes off the drill, but one mistake could have easily destroyed a year’s work.

Fortunately the surgery went without a hitch, and I got the board nicely mounted in the case. I also ditched the jury-rigged power cable you see in the photo that has caused me so many headaches, and carefully wired up new power connections, this time with a real power switch too! With the new connections, I measure 4.96 volts on the board, instead of the 4.75 or so I used to see with the old hookup.

The hardest part of this job is hopefully behind me now, but there’s still a lot of work to do fashioning new connectors from the BMOW board to the case holes, and building a small off-board audio mixer/amplifier circuit. I need to build new VGA, keyboard, USB, volume, audio, and reset cables, solder them all to the appropriate connectors, and devise some way to mount them all neatly and securely aligned with the holes in the case. Earlier I’d considered building a small custom PCB for this, but I think I’ll probably just do it all by hand. I have a strong suspicion that hot glue will play a role once again!