The Expert is a Brazilian manufactured in the 80's and it is compatible with MSX standard. It uses a detachable keyboard but it lacks the Caps Lock LED on the keyboard because the 13 pin connector used ran out of pins (even the shield is used as a 14th conductor for GND). 

One day I heard about that issue on my favorite podcast, and just for fun I have designed a Caps Lock cartrige for the Expert. Some time later I have added another feature to the cartridge that is not implemented on the computer:  a RESET button. 

I have designed PCBs for the MSX cartriges before, like the MSXDOS2 cartride that contains a ROM with the MSXDOS2 kernel with some glue logic to perform the bankswitching (the circuit was not designed by me though). Such cartridge allows the Expert - an MSX1 machine - to run  MSXDOS2 without a Memory Mapper. 

On this sunday afternoon I have merged the two projects and created the Ultimate MSX Caps Lock cartridge:

The PCB and schematics files are available on Github. I have just routed the board, not assembled the circuit yet, sou use it at your own risk.