Below are some pictures showing my KTM-2/80. I built this on a Radio Shack ASCII keyboard encoder I picked up at a flea market. All that was needed was to build the KTM in the space provided above the keyboard, cut the traces for the KTM's matrix, and install a connector between the keyboard and the KTM board.
First picture shows KTM assembled. Actual board size is 3" x 13".
Bottom of keyboard showing trace cuts and wires added for new matrix. What made this easy was the fact that each switch was labeled with its function.
Picture showing bottom of KTM. Point to point wiring using 30 gauge wire is used to save height space and looks much neater. I had to glue two boards together for the 13" length. The two blue boards shown below are were the joint was made.