In the basics, he left out a very important point, no pun intended. The condenser does NOT only protect the breaker points, it is NECESSARY to form the spark. If you remove the condenser out of a Kettering (breaker points battery) ignition, it will not start or run.
This is because, when the points open, and the coil field collapses, the voltage generated in the coil is generated in BOTH the primary and secondary. The primary voltage being generated CHARGES UP the condenser (capacitor) until the coil has completely discharged it's magnetism. At this INSTANT, the capacitor/ condenser is fully charged, and now things REVERSE. The charged capacitor now discharges it's energy BACK INTO the coil, charging the coil magnetism (flux) AGAIN. At the peak of this magnetism, the capacitor is discharged once more, the coil field is at it's peak, the coil now discharges AGAIN and AGAIN charges up the cap.
This "seesaw" ---known as "ringing", or "flywheel effect" continues until electrical losses or load on the circuit (the spark gap at the plug) finally runs down the ringing, ----just in time for the points to close and start all over
Anyone that has ever seen a scope ignition pattern should immediately recognize the above description from seeing that pattern.
In the representative pattern below, you can see this oscillation or ringing. It is damped out by the load of the spark plug firing, which is the "flat line" to the right of the initial pulse. The reason that the spark jumps up so high at first, is that it takes some "overshoot" so to speak to ionize the plug gap and get "The fire going." After the plug fires, conditions, IE fuel mixture, compression, causes a load which "pulls down" the spark voltage. Finally, the coil and cap "run out of soup" and the voltage power supplied by the coil can no longer maintain the spark. The SECOND high spike at the end of the plug firing is caused because when the plug finally stops firing, the coil has JUST enough energy, and is now "unloaded" it's voltage jumps up for a momentary spike, Finally, the final ringing at the end is where the energy in the coil/ cap is finally petering out, and further to the right, you can see the points closing, to start things all over again.
Some electronic (breakerless) ignitions such as the older NOT HEI GM stuff and the Mopar ECU used in the early 70's into the 80's essentially worked exactly the same way as breaker points, and the scope patterns look very similar.
80s GM HEI, however does NOT work quite the same way. To put it simply, HEI is designed to operate withOUT a condenser in the system
(Incidently, GM 4 terminal HEI modules are VERY adaptable, can be used with many mis-matched breakerless distributors, as well as adapted with a simple circuit to a points distributor. I'm using a GM HEI on my Toyota powered crawler, with the factory Toy breakerless dist. I'm also using HEI on my 67 Dart, with a factory equivalent Mopar breakerless dist.
A "real world" scope pattern, stolen from "that other place"
