*Model 4 is NOT for replacement of "Inverted T" Arrow key layouts. What you see below is exactly what is available. New bezel required to convert "Inverted T" style machines to standard layout. New bezels are available via links below.
Like many owners of the Tandy TRS-80 Model 4, I experienced failing keyboard contacts. I quickly learned that servicing the stock switches is difficult, time consuming, and no fun.
I designed a replacement keyboard with the help of www.Keyboard-Layout-Editor.com, Plate & Case Builder, and EasyEDA. This replacement keyboard is meant to use Cherry/Gateron MX switch footprints and match the Row/Column wiring of the original keyboard matrix as detailed on the maintenance manual schematic. It's designed so that a typical 20 Pin IDC cable connection can connect to the keyboard, and the other end to the motherboard itself. It also adds footprint support for extra keys that are supported in the ROM but were not shown in the schematic keyboard matrix. Extensive support holes are added for use as a generic retro keyboard by enthusiasts. If +5V DC is supplied via Pin 17(*** See note in project files) and an optional 330 Ohm resistor installed, a Power LED can be installed to coincide with the footprint of the RESET switch for compatible MX key switches.
To purchase parts or an assembled one, click here.
Installation instructions are here.
To purchase a reproduction Model 3 Bezel from Marcel Erz, click here.
To purchase a reproduction Model 4 Bezel from Marcel Erz, click here.
DIY Project files can be found at this link.
Video on how to build and install the keyboard if using original plate and Rev 3.4 PCB:
