Rob writes in –
Sometimes the best way to take a step forward is to take a step back in time. So Andrew Smith designed a fully-functional toy oscilloscope, made out of parts he found in his junk box, such as the EF91, EF80 and EF184 valves. Using a DC-DC converter to power the old (but still working) 7cm CRT he discovered in his loft, Andrew housed it in the same wooden box as the rest of the circuitry. The whole system runs from a single regulated 12.6V DC supply, which can be derived from a “wall-wart” PSU. Doc Brown would be proud.