I collected several ZX Spectrum series computers, but I don’t have any fancy peripherals. After several attempts I managed to buy ZX Spectrum Microdrive and interface 1 for it.
As always with ancient hardware it is working a bit, but in general not working: tape inside is moving, but nothing from the computer. The only problem, that to open this device I need to tear off the metal cover. According to original documentation, this metal cover is single use only. Now it is impossible to get new cover, so I gently took it off, but some deformation happened.
Interface box goes under the computer, there are special screws to fix it to the computer. For my experiments I was using classic ZX Spectrum.
Inside the microdrive there is one chip and 7805 voltage regulator. There are two electrolytic capacitors near the regulator: 0.22uF and 0.47uF only! Original service manual asked to check voltage with an oscilloscope. The voltage level was normal, but it was full of noise- both capacitors were almost empty. I replaced them with 10uF regular electrolyte and 1uF tantalum capacitor. Now the voltage is very clean.
Another trick is to remove capstan rubber and put it back on the other side. Now it will touch tape with a less worn side.
Inside the interface there is only one microcontroller and RS232 level converters. There is not only standard RS232 levels converter and also some transistors for some sort of “local network”.
I also replaced cable to a more “spectrum” type. At first glance, this “tape loop” system looks very slow, but compared to a similar 3″ disk drive in Amstrad CPC it is much faster! Transfer rate is quite fast, the only slow part is seek and search.
Another problem is felt pad inside cartridge- it deteriorates very fast after so many years of usage and storage.