I thought I'd revisit the original Spectrum and got hold of a +3 in need of attention. Once spruced up, I set about redesigning the simple IDE interface in KiCad. I have been using KiCad for several months and I am warming to it. Now having completed several projects with it.
The IDE interface is pretty easy to construct. The only problem may be finding the 34-way edge connector. I found a seller on eBay who supplies uncut edge connectors (http://www.ebay.co.uk/usr/retrocomputershack?_trksid=p2047675.l2559) It is a fairly simple task to cut the edge connector down with a junior hacksaw, pull the two contacts out where a key is required and use a piece of scrap PCB as the key. I wouldn't recommend using the interface without a key, it's too easy to short out connections and fry your computer in the process!
After assembly is complete, you will need to follow instructions on the World Of Spectrum pages to produce a pair of +3e ROMs and fit them inside the Spectrum's case. Having done this, attach the interface on to the rear of your Spectrum and then a standard ribbon cable from your IDE device to the interface. Pay attention to where Pin One is at both ends. I used an old hard drive. I have attempted to get a CF Card adaptor working but with no success so far. I will post here if I manage to do so.
Power the IDE device first, then the Spectrum. After a pause, you should see a copyright message like this:
Now follow the instructions on the World of Spectrum pages for preparing your device.