if you want to see a real interesting way of getting all of the magnetic and electrostatic variables to match and keep the beams focused and converged, see if you can find an old 1960's vintage color TV. the wave shaping circuits that added correction voltages for the focus and convergence were very complex LCR networks, and there were adjustments for every area of the screen (and they also interacted so much, you usually had to do the whole alignment several times to get it right). one of the reasons these convergence networks were so complex, was that instead of the electron guns being arranged in a straight line, they (and the phosphor dots on the screen) were arranged in a triangle. Sony's introduction of the inline tube (Trinitron) with phosphor stripes rather than dots, allowed the convergence to be done primarily with magnetic rings on the yoke. i definitely prefer the magnetic ring convergence adjustments, and can do them in less than 1/5 the time it would take to do the old convergence panel adjustments. i haven't had to converge a tube in about 8 years or so, and the only reason i did them after about 1998 was that i had client with a bunch of (externally identical, but not identical internally) monitors, some with bad tubes, some with bad guts, and not all of the yokes were interchangeable.