I found this project on github when I had some repair tasks.
I modified the circuit at severeal points and adapted it to my capabilities:
- I use Android NANO module, because it contains all the necessary components: quartz crystal, reset button, ISP connection and even a 5V LDO too - it is matter, because the USB does not provide stabile 5V all the time, it depends from computers, USB-PSUs, USB-HUBs...
- I put the 4116 adapter into the board, which separated with a jumper array
- I use my proven power supply for +12V and -5V: it provide +12V with a MT3608 module (the trimmer potentiometer is changed to fix resitors)
The -5V maker is same solution that the original ZX-Spectrum uses: it connects into the pulse point of MT3608, makes cca. -12V with voltage doubler then stabilizes the -5V with zener diode - the zener stabilization is sufficient because the 4116 DRAM -5V consuption is little, max. ~200uA (you can see it on my own made ZX Spectrum boards too).
