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Let's look at some pictures.
I literally had about $10 to build this in '91 from odd parts, some LEDS and 7406s, lots of heat glue and a cardboard box. This is the front panel. It can hook right up to the Z-80 bus. The thing in the lower left is eight S/R flip flops using 7400s wrapped in electrical tape and using paperclips as contacts. See the plastic sleeve for the red wire that taps out bits? I built this particular piece for no money in '89. Can you tell that I like heat glue??
Here are the lamps I use. They are T 1 3/4 mini-flanged 330 aircraft lamps. They are very cool for binary display panels, don't you think? The bulbs come out through the front.
Here is a scan of the keypad schematic I wrote up in '92:
Here is the whole homebrew computer running the input.txt program. I finished this in '93.
Here is the homebrew running the prog.txt GWBASIC program. It really does write prog.--1 to the leds.
I never did like the way that multiplexing looked. That is why I drove the 7-segment displays with (8) 74ls374 latches connected to (8) 74ls244 buffers w/ (2) 330 ohm resisters in parallel for each segment.
Here is a look at the inside of the homebrew:
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