Modding additional thumb shift keys into my Filco Majestouch Convertible 2

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Hello there! I have been reading posts on this forum for awhile and decided to finally make an account to post my custom JIS Filco Majestouch Convertible 2 [FKBC108MC/JB2] keyboard. A note for anyone outside of Japan looking to purchase this (or another Filco keyboard) I recommend just importing one yourself as long as customs and shipping would not be to expensive for your country as they generally cost about $50-$100+ USD more outside Japan.

This was my keyboard before the mod (You can see my custom printed key-caps and replaced LEDs from eye piercing blue to dimmer green)



I recently found this blog http://hieroglyphe.blog47.fc2.com/?tag=%E3%82%AD%E3%83%BC%E3%83%88%E3%83%83%E3%83%97 which inspired me to do a similar mod but in a much more factory looking way.

I started by cutting through the metal plate and PCB on either side of the space bar with a rotary cutting tool to make room for the extra cherry switches and stabilizers for the shorter size space bar. When doing this I recommend you cover up all the cherry switches so metal dust does not get in them, this happened to me. Also creating to much heat from the cutting wheel ruined the switches near where I cut and I needed to replace those. I also need to re-route a trace that I cut through but I expected to have to do this before I started this project.




After getting all the cuts made and the switches located and mounted where I wanted I filled the holes in the PCB with heat melt glue to secure them more long-term while still being relatively easy to remove should I want to reverse this mod. I could have just wired the switches to one of the already existing keys on the keyboard effectively duplicating it but I wanted these to be completely separate keys so if I were to re-map them with software it would not effect any other key on the keyboard. I decided what I should do is add a separate keyboard controller for the extra thumb buttons so they can act independently from all the other keys, I removed all the switches from a Razer Blackwidow Ultimate 2013 and cut the controller portion out of the PCB which I then wired the switches to. I needed to cut a hole in the bottom of the case to make room for the USB connection which was to thick to fit inside the case. I also needed to remove all ports  from the Razer PCB to allow it to be thin enough to fit inside the case. Electrically they are num pad "+" and "-" (I do a lot of design so its useful to use as zoom in/out) but I remap them to other things using Razer Synapse software under Windows. When I am typing they function and "backspace" and "enter" which is very useful when typing Japanese as you use "enter" almost as you would "space" when typing English. (For confirming IME suggestion/transformation)




I then matched the lengths of the cables and sleeved them so they look as one cable coming out of the case, I also ordered more custom printed key-caps for the modified keys.



The last thing that I did was shape the space bar so that my thumb does not rest on a sharp corner, I used a "rasp/file" (used google translate) (one of those things that you use to shape metal and wood ) It is actually quite comfortable, even more so than the space bar of most factory mechanical keyboard style space bars. Here is the finished product!