I still have mine in the loft somewhere, built by my own fair hand in 1980!
I recall having to solder 113(!) chip sockets and having to align all the keyboard pins to solder it to the motehrboard.
I upgraded mine to a whole 10K of RAM, which I think cost me about £35!
It worked first time, but I had random characters on the display. I called Acorn and asked for technical support, only to be told, "He's on Holiday" I finally found a bent pin on the video controller ship and it worked fine, and continued to do so.
Might even work now if I can find it...