Early reZet80 history

In the 80s I coded in Z80 assembler on my Spectravideo SV-328 (MK 1).
I also had a Mini Expander (SV-602), an RS232 interface adapter (SV-805) and a serial dot matrix printer (I think it was a Seikosha but I'm still hunting for the proof photograph in the attic).
I remember being very excited about the available Z80 hardware but I never attempted to build my own (I guess coding in assembler was enough of a challenge for a 16-year old teenager in 1983).
Now that I started my reZet80 project in 2016 and I'm designing my own hardware I decided to document my early attempts at electronics.
Stage 1:
I built every component on its own PCB.

I used colored wires for address, data, control in, control out and clock signals I connected to a breadboard.

I used a nonvolatile SRAM chip so I didn't have to bother about keeping ROM and RAM apart.

Program was enterd via DIP switches on the debug board.
I used a sigle-step circuit as clock together with the blinkenlights board to debug every single instruction.

I used a power regulator right from the start.

And I connected my old competition pro mini as input port.

I was able to follow the CPU signals after every clock cycle. But somehow I managed to erase the nonvolatile memory from time to time. And my results were not reproducible all the time.