This instructable describes the construction of a extremely simple 12v oscillosope.
The diagram below is a schematic of the Mullard pupil's oscilloscope. This is a single valve (+CRT) oscilloscope that is about as simple as an oscilloscope can get. The Mullard scope is described in the Radio Basics column of Practical Wireless March 2005.
Step 1: Transformer Winding
The transformer was home wound on a ferrite core that I had handy and an aluminium clamp fabricated to enable it to be fixed to the chassis.
Transformer Winding Details:
L1,L4 12 turns 26 swg
L2,L3 3 turns 26 swg
L5 450 turns 36 swg