After a long hiatus I decided to start anew. Now, I'll be using smaller boards (24*30 holes, 7*9 cm), display will have only 4 digits, overall design will be more modular. Each board will have more manageable amount of components, so it should be easier to debug, or at the worst scrap and make new one.

Here is the first board, which will be the front one. It has digits and 2-to-4 decoder, which selects which digits to light.

Other boards are: 4-to-16 decoder, 16-to-7 encoder (from which signals should drive display of digits) and multiplexor (4x 4-to1 mux), with 16 bit input and 4 bit output, this will be driven also by decoder on front board. At first, for 16 bit word switch bank will be used. At some future time I am doing to make 16 bit register, so this display should be able to read contents of that register and display it as hex number.