Earlier this year while browsing Reddit, I came across this post which seemingly showed a DS Lite with TV output. I thought that the project was extremely cool, and that I should make some of the boards since everything is documented on the github page for the project. It took me a few months to finally get everything planned and ordered, and another 5 hours to assemble the boards, but I did manage it. The circuit boards came from JLCPCB, and the parts were ordered from Mouser.
The hardest part of assembly was soldering the 45 pin fpc connector to the board as it was hard to line up, and even harder to solder without bridging pins. After 2 1/2 hours of soldering, cleaning, and inspecting the solder joints under a usb microscope, I had 2 of them soldered well enough to be usable. It took another hour or so to solder the rest of the components, and at that point, the boards were almost ready to be used after being cleaned with 99% IPA. 
Butchered shell of my first trial.
As for the DS Lites themselves, one was bought from Facebook Marketplace, and the other one was a mix of parts from a DS Lite bought on Kijiji, and on eBay. The preparations started by carefully removing the top screens from the units as they still worked. The next step was to modify the bottom shell to allow the ribbon cable to pass through between the shell and the left button. I had originally done this modification by removing the plastic on the top of the shell, but this ended up looking highly unprofessional. The next approach was to just notch out the plastic above the left button as shown in this guide (Step 3, point 2). At this point, I had butchered a shell, and needed to find another one to fix my mistake. I ended up taking the face plate from a Gameboy Macro Lite mod that I had done leaving me with a DS Lite that had a black back plate, and pink face plate. As for the silver shelled DS Lite, it was originally a white shelled DS Lite, but since the shell was in really nice condition, I couldn't go through with modifying it so I ended up taking the bottom half of an old ds shell I had lying around instead. Hence the white screen border and silver shell.
The fully assembled tv out boards attached to their respective DS Lite.Since I didn't buy two sets of av ports (don't know why I didn't), I had to salvage some connectors for the time being so that the board could be tested. Eventually this would be resolved by removing the ports from a 3 port av switch.
Nothing is more satisfying than having your newly soldered project work the first time. The two units pictured to the left were my assembled DS Lites after the boards were cleaned the first time. They went through testing, and I knew that the video output as well as the buttons on board for swapping screens, and picture in picture mode were working. Eventually I would also test the audio and hear that the tv was playing sound.
In the end, it was a fun project, and one that will certainly be used in the future to capture gameplay of Pokemon games, or other DS games I'm playing. Going forward, a 3d printed shell to protect the circuit boards, and ribbon cable need to be created. I already have ideas of how it'll be implemented, and will update this project page when the model is finished and has been tested.
Since the time this page was originally written, another modification was made to these DS systems to internalize parts of the mod, and to wire up the AV output to the headphone jack. This took inspiration from Rhotronix and was a simple modification. I also created a 3d printed piece to cover most of the circuit board on the back of the ds lite to protect it and the ribbon cable. All that's left is to play GBA and DS games on the big screen.
