Electronica band SubAtomicGlue has a great step-by-step, blow-by-blow account of building and troubleshooting an x0xb0x kit. They call it the xoxl0g.
If you’re not familiar with the x0xb0x, it’s a circuit-accurate recreation of the electronics of the popular TB-303 bassline synth, with an updated sequencer and some goodies like MIDI and USB connectivity.
The blog takes you from starting with a box, through this:
All the way through the completion of x0xb0x #121.
Interesting for synth lovers and acid freaks alike. If you have any doubts about the authenticity of the x0xb0x electronics, check out acid sounds of SubAtomicGlues’s x0x jam session.