Sinclair Interface 1
Interface 1 ULA replacement
The ULA is most important chip inside the interface. However, the most damageable. So, there's an idea to build a replacement from TTL SMD chips.
Microdrive on cassette tape
There's an idea to build Microdrive using ordinary tape recorder with auto-reverse.
Another idea is to build Micridrive replacement using 8051 microcontroller. It would possess a 512kB PEROM and simulate 4 cartridges.