November 25, 2016

Add Thumb Keys Into a Mechanical Keyboard [Filco Majestouch Convertible 2]

If you have a mechanical keyboard with Cherry MX series switches or a similar switch type like OMRON B3G series or ALPS SKCL/SKCM series it is relativity easy to add and or re-position the layout of keys to your liking. These types of switches are their own separate module instead of using contacts on the PCB like rubber dome or Torpre keyboards making it easy to place them wherever you want and wire them manually fairly easily, the hardest part is cutting new mounting holes into the switch plate.

Inspired by this blog: hieroglyphe.blog47.fc2.com tag=「キートップ」 I decided to do a similar mod but in a way that looks nearly factory by using standard size key caps and getting the extra keys custom printed to match. Since I am right handed I made "Space" key usable with my right thumb and the 2 extra thumb keys usable with my left thumb. These 2 extra keys can function as the following: [Enter/BackSpace] [+/-] or [Space/Enter] and are configurable with switches at the back of the keyboard.

[Before] [After]

Build Log:

After disassembly of the keyboard I first started by cutting the switch plate around the space switch where I was originally going to add the extra thumb buttons (one on each side of space bar) This ended up being a bit uncomfortable so I changed the layout as you will see later on. To do this I used a hand held rotary tool with a cutting disk. The switch plate on this Filco board is very thick compared to most keyboard I have seen and required the cutting wheel to contact the metal much longer that I would have liked, this caused a large amount of heat to get into the switches and warp the contacts (as well as lots of metal dust from cutting) If you decide to do this or a similar mod I recommend either removing the nearby switches first or covering them and being very careful not to heat soak the switch plate.

Here you can see the finished cuts, I also cut the PCB from the other side to make room for the switch leads. Please take caution when cutting PCBs as they are often fiberglass which can be harmful when inhaled, use a mask. At this stage I was not worried about cutting though any existing traces as I would re-wire any traces that I had cut manually later. You may also notice the missing switches, I started replacing the broken ones at this stage, in total I had to replace about 20 switches.

Here is a shot of how the switches and stabilizer fit into the newly cut holes.

I then put the keycaps on the switches and aligned them before tacking them down with a little hot glue.

Originally I wired the new thumb buttons to the controller portion of a Razer Blackwidow Ultimate 2013 so I would use the Razer Synapse software to control them, while this worked exactly how it should have I was quite annoyed by Windows installing the "US English" keyboard layout every time the Razer controller was connected. This controller is also plagued with random key repeat issue, one of the many reasons I stopped using the Razer keyboard in the first place. I decided to remove the Razer controller and wire it in such a way that I can use it with out any extra software and still have the same functionality over Bluetooth.

When I had the Razer controller inside my keyboard I sleeved the 2 cables together like this.

A close up of my custom printed key caps from WASD Keyboards.

After a few days of use I decided that this layout was not as comfortable as I liked so I took the keyboard apart again and arranged the keys as shown. I also reshaped the space key with a rasp as I planned to do from the start, this makes it more comfortable than the original space bar.

Here all the wiring on the board is finished, I just needed to attach the switches and mount them in the case. You can also see the method I used to secure the switches into the frame, lots of hot glue, this works very well and is still removable if you decide to change or revert the layout in the future.

Key remapping switches wired.

Again I used more hot glue to secure the switches into the slot I cut out of the rear of the case.

The finished product!

View of the key remapping switches from the back, the only thing that hints that something has been modified.

I created a custom label with the added switch functions listed.

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