Exploring vector rescanning.
Found this video (it's not mine) but I'm experimenting
using the LZX modular system to do a similar thing.
Input the video signal into the z-input of your scope and supply the X & Y inputs with
The circuit uses a LM1881 IC - Its a video sync separator.
Here is another video using the same idea:
Creating X and Y sawtooth ramp signals from the vertical and horizontal sync pulses.
Schematic is here:
Using a Tektronix 485 in XY mode
There is a useful muffs post on Vector Rescanning