As someone with an affinity for both wireless devices and mechanical keyboards, I am saddened that wireless mechanical keyboards are few and far between. Only a handful of models exist, and unfortunately none of them quite fit my tastes. For this reason, I decided to go with a DIY approach. I figured since I had already voided the warranty on my Das a while back (with the vinyl wrap), I'd just go all the way and make the thing wireless.

This build log can serve as a guide for doing wireless mods in general. The process should be the same for most keyboards.

Phase 0: Planning

After a bit of research, I decided upon a method that is essentially replacing the internals of the mechanical board with that of a wireless one. The mechanical switches would be wired to replicate the membrane matrix of the wireless board, and connected to the wireless board's controller. This seemed like a straightforward, reliable, and cost efficient approach.

Being my first attempt at this, I decided to go for the least expensive board I could find. I ended up choosing a HP K2500 to be the donor keyboard since it had the same (104-key) layout as the Das and minimal amount of additional features. The small USB dongle was also nice.

The donor keyboard - HP K2500

Final shot of the Das before the transformation.

Phase 1: Dismantling

Not much to say about the wireless board, everything came apart after removing the screws. 

K2500 disassembled

Things get a bit complicated with the Das, since all switches had to be de-soldered in order to separate the PCB.

Underside of the Das' circuit board; K2500 matrix and controller can also be seen

There are other ways to isolate the switches from each other, such as scratching out all the connections, which may be more practical on other keyboards. I opted to remove the whole PCB just to be safe. Doing so would also leave me with a functional keyboard controller and PCB in case I ever need it in the future.

PCB separated

At this point with the PCB off, I noticed that the switches were a bit loose with only the backplate holding them, so I went ahead and secured them with some hot glue. In hindsight, I should have done this after the wiring, as then I could have also glued down the wires at the same time and do everything in one pass. Also, the glue would not have gotten in the way as it did occasionally during the wiring.

Keys glued in place

Phase 2: Wiring

Wiring all the switches will easily take up the bulk of the modification process and will depend heavily on one's soldering proficiency. The general procedure I used goes as follows:

For each of the 26 pins on the controller: {

* Trace its path on the membrane and make note of all the keys it runs
  through.
* Mark the corresponding switches on the mechanical board, and wire
  them together.

}

Mapping one continuous run of keys from the wireless membrane to the mechanical switches using red inspection arrows

Some useful advice for this process:

* The connection paths on the membrane are often unnecessarily long and
  winding in order for them not to cross each other. The switches do
  not have to be wired in any particular pattern, as long as they are
  all connected.
* Using a different color of wire for each run will make things easier
  on the eyes. Either way, double and triple-check before and after
  soldering.
* Depending on the keyboard, the space behind the backplate may be
  tight, it is best to keep the wiring as neat as possible. Thinner
  wire also helps.
* Being consistent also goes a long way in keeping the wiring neat. One
  thing I did was wire all the runs from the top membrane to the
  thicker pin on each switch (and vice versa).

All wired!

Close up on controller

After soldering everything, I hooked up the batteries and did a quick test to see if everything was wired correctly. Once I made sure every key worked as it should, I went ahead with the final assembly.

Phase 3: Assembling

Firstly, I did a quick fit to make sure there was room for everything inside the case and finalize the placement of the internals. 

Testing the fit

As you can see, everything fit nicely (and with ample room to spare thanks to the Das Keyboard's signature "hump").

Now came the matter of securing the controller and batteries in place. I had originally planned to 3d-print some sort of custom bracket structure. However, since I didn't have access to a printer at the time, I turned to some good ol' improvisational ingenuity...

The raw materials...

After scavenging around the house, I settled with two plastic clips that held a pen in its packaging and a cap for the end of a DVI cable. Together, they made a crude but effective battery compartment.

...for when you don't have a battery pack.

Next, I took an old graphics card cooler that was lying around and cut out a rectangular chunk of plastic. I glued this to the backplate so that it would press down on the controller and secure it in place.

This area of the cooler here...

...ended up here.

Finally, I wanted to do something to address the empty slots originally used for the USB passthroughs, as well as the hole at the top where the cable once was. 

Bits of plastic also cut from the cooler

Noticing that the plastic from the graphics card cooler was similar enough, I carefully cut out and sanded these pieces to fill the gaps. They actually turned out better than I was expecting since the color and and texture was a near-match. 

I was quite happy with this until I managed to get glue all over the edge as you can see here. I ended up sanding it down which meant losing the textured finish on the plastic. (Oh well.)

All done! :D

Final thoughts:

Overall, everything went smoother than I had anticipated. (I think software development has conditioned me to expect roadblocks.) The most challenging aspect of the entire process would be the soldering, since I had limited experience with that. 

For anyone looking for a list of tools and materials used, here is a rough overview of the stuff required since I didn't include an explicit list anywhere:

* Soldering kit (soldering iron, solder, solder removal tool/wick, wire
  stripper, tweezers)
* Lots of wire (I believe I used 30 AWG)
* Whatever else required to do the job (glue, tape, power tools, etc)

That's it for the build log. I probably could have taken more pictures along the way, but hopefully my explanations are clear enough for most parts.

Some additional pics of the keyboard are here.