The ZX81 also had the honor of being one of the first "sure you can get it in a kit" computers. I got mine this way, and at the time, (I was 12) it was a devil to put together. but once you hooked the Z80 up to all the other transistors and so forth, there was hardly anything that could go wrong. Except the infamous "RAM Pack Wiggle", whereby the much coverted 16K Ram Pack, which plugged into the "expansion slot" in the back of the ZX81, would wiggle, and dump RAM mid way through a programming session. this really burned after hours of tapping on the silkscreen keyboard, forgetting to save, then being forced to load the program in via cassette tape, which was hit or miss at best. Also margeted under the name "Timex-Sinclair 1000".