[Oldcodger]

It does seem that when it comes to electrics a lot of common sensed folks minds seem to turn to jelly. I regularly post on a car forum and number of times I see the "change this/change that " approach to an electrical problem amazes me. Perhaps, I'm blessed with a decent engineering background, which applies to mechanical s and electrics,but I'm of the old school of "how does it work, what is not working ,and then look for a solution".
Simple example- car lamp not lit- no supply or faulty lamp.
But what needs to be taught is the half it and see technique. It doesn't matter if the fault lies on a light circuit to the top yard of a farm/ a transatlantic circuit or a track on a PCB, for simple no voltage faults. More complicated faults might involve the introduction of capacitors in a circuit to check for open circuit ones, or voltage checks on the cathode of valves, or legs of transistors, but that needs a lot of theory.